JPH0768357A - Twin-drum type flat nozzle for continuous casting - Google Patents

Abstract

(57) [Summary] [Purpose] In a flat outer nozzle for twin-drum type continuous casting, which has an inner nozzle in the upper part, a meltable metal and a rectifying refractory (filter) in the lower part, and a slit nozzle hole in the lower part. Using a rectifying refractory with a large number of through-holes that can be obtained easily and at low cost, the outflow distribution of the molten metal flowing out from the slit nozzle holes can be made more uniform, and the molten metal from the tundish can be stably supplied into the moving mold. Provide a flat outer nozzle structure capable of. [Structure] A rectifying refractory having a large number of through holes is arranged on the bottom, and a mesh is arranged on the upper part of the refractory so that the upper space of the mesh and the slit-shaped nozzle hole are communicated with each other. The hole diameter of the through holes in the rectifying refractory is 2 to 30 mm, the hole area ratio in the rectifying refractory is 10 to 30%, and the hole area ratio of the through holes in the rectifying refractory or the through holes. The flow resistance of the molten metal was different between the central part and both sides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat outer nozzle structure for a nozzle used when a molten metal is supplied from a tundish into a moving mold in a twin-drum type continuous casting apparatus.

[0002]

2. Description of the Related Art In continuous casting using a conventionally known twin-drum type continuous casting apparatus, as shown in FIG. 5, a pair of rotating cooling drums Ra, Rb and both ends of the cooling drums Ra, Rb are provided. 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 side weirs Sa and Sb in contact with each other to form a molten metal pool p of a predetermined level in the moving mold. Meanwhile, a solidified shell is formed by cooling with a cooling drum, and the solidified shell is pressure-contacted and integrated in a gap formed at the closest portion of a pair of cooling drums to obtain a wide thin cast piece c. At this time, in order to obtain a homogeneous slab, it is necessary to suppress the positional fluctuation of the meniscus formed in the moving mold as much as possible, therefore, the control accuracy of the supply amount of the molten metal in the moving mold, further Yu It is is required.

In order to meet such a demand, for example, in the invention of JP-A-63-203254, a nozzle having a filter made of a porous refractory and a fusible metal member is proposed. The nozzle shown here is shown in FIG.
As shown in Fig. 4, the lower part of the inner nozzle a is internally installed in the upper opening of the flat outer nozzle b, and the outer nozzle is flat, and the slit-shaped nozzle hole is formed in the side wall near the lower closed end (bottom part). o is formed.

Here, as shown in FIG. 6, a porous refractory f and a fusible metal member d are incorporated in an outer nozzle b.
A high pressure loss is applied in the outer nozzle b during the casting start, the outer nozzle b is filled with the molten metal, and the tundish, the inner nozzle a, the outer nozzle b, and the molten metal in the moving mold are densely continuous,
I try to cast. However, when this flat outer nozzle is used, it is difficult to maintain a uniform outflow distribution in the axial direction of the cooling drum of the molten metal that flows out from the slit-shaped nozzle holes o when the molten metal is supplied from the inner nozzle.

That is, in general, since the through holes of the porous refractory material (filter) are formed uniformly over the entire area, the amount of molten metal flowing out at the central portion, which is close to the nozzle holes (slit holes) of the inner nozzle. In many cases, the molten metal outflow tends to decrease on both sides thereof, and it is inevitable that the meniscus position in the moving mold is high in the central portion in the axial direction of the cooling drum and low in both sides thereof. Further, the porous refractory used here has problems in terms of economical efficiency and long-term stable casting.

As an example of the method for producing this porous refractory material,
There is an example in which urethane foam is used as the material of the skeleton, and the skeleton is coated with mud mixed with refractory fine powder and a binder several times and then heat-treated, etc., but the urethane foam used as the material is bedding, etc. Many of the cushioning materials are mainly manufactured, and the hole diameter varies considerably depending on the manufacturing lot due to the manufacturing method.

When this is used as a porous filter material used for the purpose of supplying the molten metal that is uniformly rectified from the discharge port of the flat outer nozzle, it is necessary to carefully select and control the pore size. If neglected, uneven flow will occur in the molten metal flow out of the discharge hole, and in extreme cases, a wavy phenomenon will occur in the moving mold, inclusions will be involved, and it may cause scratches or wrinkles on the slab, or the occurrence of hot bands. This may cause troubles such as melting of a cast piece or interruption of casting due to insufficient molten metal for casting.

[0008] As a manufacturing process of this porous refractory material, a material such as urethane foam is coated with mud mixed with the refractory material and a binder, and the excess coating material at the clogging site is removed to ensure that the coating material has sufficient strength. Heat treatment or natural standing until repeated until the specified strength is obtained, the labor cost required for the work increases, and as a coated refractory, durability, thermal shock resistance, etc. are required.
Since there are many cases where raw materials such as ₂ O ₃ and Zr ₂ are used, when a filter is formed from such a porous refractory material,
Its price becomes very expensive.

The thickness of the urethane foam skeleton coated with the refractory layer varies depending on the manufacturing method, but the pore size of the porous filter is limited, and a thickness of several mm is customary. There is a concern that the casting amount may be limited to a small amount in terms of durability.

Separately from this, when it is used for steel types such as aluminum-killed steel with a large amount of deposited deposits such as Al ₂ O ₃ , the skeleton of the porous filter changes with time,
The deposits are repeatedly accumulated, and eventually the porous filter is clogged, so that the target casting amount cannot be obtained, and it is often necessary to give up casting during casting.

[0011]

DISCLOSURE OF THE INVENTION The present invention is for twin drum type continuous casting in which an inner nozzle is provided in the upper part, a meltable metal and a rectifying refractory (filter) are built in the lower part, and a slit nozzle hole is provided in the lower part. In the flat nozzle, this straightening refractory material (filter) is formed of a refractory material that is easily and inexpensively obtained, and the outflow distribution in the axial direction of the cooling drum of the molten metal flowing out from the slit-shaped nozzle holes is made more uniform. It is intended to provide a flat outer nozzle structure capable of stably supplying molten metal from a dish into a moving mold.

[0012]

According to a first aspect of the present invention, in a flat outer nozzle for twin-drum type continuous casting having an inner nozzle insertion hole in an upper portion and a slit nozzle in a lower end portion, a large number of flat bottom nozzles are provided. A rectifying refractory having a through-hole is provided, and a net-like body is provided above the refractory. The upper space of the net-like body is communicated with the slit-shaped nozzle hole, and the side wall is provided with an electric heating electrode. A twin-drum type flat outer nozzle for continuous casting characterized by being arranged.

A second aspect of the present invention is the same as the first aspect, wherein the rectifying refractory material is Al ₂ O ₃ , MgO, CaO, SiO ₂ , ZrO.
_2. A twin-drum type flat outer nozzle for continuous casting, which is formed of a refractory material composed of a single component of SiC, C, BN or a composite component thereof.

According to a third aspect of the present invention, the twin drum continuous type according to the first aspect is characterized in that the diameter of the through-hole in the rectifying refractory is set to 2 to 30 mm and the hole area ratio in the rectifying refractory is set to 10 to 30%. Flat outer nozzle for casting. Claim 4
The flat outer nozzle for twin-drum type continuous casting according to claim 3, wherein the hole area ratio in the rectifying refractory is small in the central portion and large in both side portions.

A fifth aspect of the present invention is a flat outer nozzle for twin-drum type continuous casting according to the first aspect, wherein a flow resistance portion is formed in a through hole of the rectifying refractory material. A sixth aspect of the present invention is the flat outer nozzle for twin-drum type continuous casting according to the fifth aspect, wherein the flow resistance in the through hole of the rectifying refractory material is large in the central portion and small in both side portions.

[0016]

In the present invention, since a relatively inexpensive refractory material obtained by a very general manufacturing method is used, and a through hole can be formed in the refractory material by drilling, for example, it is extremely easy and low in cost and high in cost. A porous refractory having accurate through holes can be obtained. Further, by changing the combination of the mesh and the through-hole diameter (2 to 30 mm), the number, and the hole shape (flow resistance) of the through holes of the porous refractory material thus obtained,
It is possible to rectify the molten metal supplied to the moving mold through the slit-shaped nozzle holes, remove inclusions and finely control the amount of molten metal, the flow velocity, for example, by selecting the hole area ratio or the flow resistance of the through holes, The effects of making the outflow distribution of the molten metal from the slit nozzle holes uniform, reducing the fluctuation of the position of the meniscus in the moving mold, stabilizing the continuous casting, and facilitating homogenization of the cast pieces can be expected. Furthermore, since the temperature of the molten metal can be maintained uniform by heating with an electric heating electrode, Al
_It enables stable casting for a long period of time even for steel grades such as aluminum-killed steel that produces a large amount of ₂ O _{3 and the} like.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiment shown in FIG. A twin-drum type flat nozzle for continuous casting to which the present invention is applied includes an inner nozzle 1 and an outer nozzle 2. An insertion hole 2a for accommodating the inner nozzle 1 is provided above the outer nozzle 2.
Is provided at the bottom, and a multi-layer (3) made of a meltable metal for imparting a pressure loss to the molten metal from the nozzle hole of the inner nozzle 1 is provided.
Layer) and a rectifying refractory 4 for rectifying the molten metal flow having a large number of through holes 4a are built in, and a slit-shaped nozzle 5 for letting the molten metal flow out to the moving mold is provided on the side wall near the lower closed end. Is provided. Also, on the side, the outer nozzle 2
An electrode 7 for lowering the thermal shock to the rectified refractory material 4, preheating for preventing the solidification of the molten metal, and energization heating for adjusting the temperature of the molten metal is attached, and the upper wall is filled with the gas filled in the outer nozzle. A degassing hole 6 is provided for discharging the liquid and confirming that the outer nozzle is filled with the molten metal. Since the lower part of the outer nozzle 2 is electrically heated,
The refractory used here is formed of a conductive Al ₂ O ₃ refractory containing carbon such as graphite or ZrB ₂ mixed therein.

The fusible metal forming the reticulate body 3 used here has a melting point equal to or lower than that of the cast metal,
It is preferable that the outer nozzle 2 is not completely melted until the outer nozzle 2 is filled with the molten metal and the molten metal flow is continuously continuous. In the case of casting metal such as steel, which does not become an inclusion in the molten metal, SUS304 is used.
Is preferably used.

This fusible metal is assembled into a wire-like wire having a mesh area of 10 to 20 mm ₂ by a wire having a diameter of 0.5 to 3 mm, and 2 to 5 sheets are piled up to form a multi-layered structure. For example, it is necessary to bundle them with a numbered wire so that they do not come apart or float up, and this numbered wire is fixed by being sandwiched between the side wall of the outer nozzle and the side surface of the rectifying refractory material. The use of multiple layers is effective in appropriately diffusing the drop impact of the molten metal from the inner nozzle 1 and smoothing the continuity of the molten metal flow, and is also effective in enhancing the meltability of this fusible metal. is there.

The rectifying refractory material 4 is not obtained by the conventional manufacturing method, but for example, a refractory material obtained by molding and firing by a very general method is penetrated into a large number by drilling, for example. Holes formed, or those obtained by embedding a large number of rods in a tension state during molding and firing, and then pulling out after firing to form a large number of through holes. Desired hole shape, hole diameter, number of holes, etc. It can be formed extremely easily and inexpensively.

Further, since the rectifying refractory 4 is to be electrically heated in order to alleviate thermal shock, preheat for preventing molten metal solidification, and adjust temperature of molten metal as described above, it is conductive like the outer nozzle 2. Although it can be said that it is desirable that the refractory with, it is not essential, for example, the generation of many grades of _{Al 2 O 3, CaO, Al} 2 O 3, ZrO 2, BN, C
In the casting in which the single component or a combination of these components is effective and durability is important, Al ₂ O ₃ , MgO, ZrO ₂ , B
A single component of N and C is effective. Further, for casting in which importance is attached to economy, a single component of SiO ₂ , Al ₂ O ₃ and C or a composite component thereof is effective.

The hole diameter and quantity of the through holes 4a of the rectifying refractory material 4 differ depending on the size of the flat outer nozzle 2, the casting amount per hour (sheet thickness, drawing speed) and the steel type, and depending on these casting conditions. Although it can be freely selected, the proper range of the pore size can be said to be 2 to 30 mm through some experiments. If it is 2 mm or less, the molten metal cannot pass through the through-hole due to its surface tension, and if it is 30 mm or more, the melt flow after passing through the through-hole 4a is disturbed, and the corrugation phenomenon (disturbance of the meniscus position) of the melt in the moving mold is generated. There is a risk that wrinkles may occur on the slab.

Regarding the shape and arrangement of the through holes 4a,
Impurities in the molten metal should be taken into consideration so that they can be precipitated and removed in the refractory in the through holes and the flow velocity of the molten metal can be controlled. Regarding the hole shape, a straight shape as shown in FIG. 2 (a) is generally used. However, S (W) as shown in FIG.
The through holes 4a are formed so as to have different flow resistances even if the through holes 4a have the same area by adopting a V shape, an inclined hole shape like (b), a female thread shape like (c), or a mortar shape (d). It is also possible.

From the viewpoint that the molten metal flows out uniformly from the entire slit-shaped nozzle hole 5 of the flat outer nozzle 2, in the rectifying refractory, for example, the distance (at a distance) from the nozzle hole of the inner nozzle 1 to the outer nozzle 2 When the amount of molten metal from the slit-shaped nozzle holes 5 is different, by combining through-holes having different large and small hole areas, or through-holes having different flow resistances, as a result, the slit-shaped nozzle holes 5 of the outer nozzle 2 can be made uniform over the entire area. A quantity of melt can be fed into the moving mold.

For example, this varies depending on the position, size, orientation, and molten metal outflow condition of the nozzle hole of the inner nozzle 1. (1) In the straightening refractory material, the area of the central through hole near the inner nozzle 1 The ratio is made small, and the area ratio of the through holes at both ends far from the inner nozzle 1 is made large. (2) In the rectified refractory material, the hole area ratio of the through holes is made the same, and the flow resistance of the molten metal in the through holes is made large at the central portion close to the inner nozzle 1 and small at both side portions far from the inner nozzle 1. It can be realized by the above.

It is effective that the deaeration holes 6 are densely filled with a plurality of wires and gas (air) is discharged to the outside of the outer nozzle 2 through the gaps between the wires. The reason is that the filled molten metal comes into contact with the wire and solidifies to form a sealed state.

As shown in FIG. 4, the flat outer nozzle 2 of the present invention having the above-mentioned structure has the inner nozzle 1 mounted on the tundish 8 side in the opening 2a at the upper part thereof to form a twin drum. A flat nozzle for continuous casting is constructed.

The inner nozzle 1 is inserted from the inside of the tundish into an insertion hole 10a formed by a refractory block 10 arranged inside the outer skin 9 of the bottom of the tundish, and its upper part is fixed. , The lower part is the insertion hole 10
It penetrates through a and projects below the tundish. The lower end of the inner nozzle 1 is a closed end, and a nozzle hole 1a is provided in the side wall near the closed end.

Above the inner nozzle 1, a stopper 11 for controlling the amount of molten metal supplied from the tundish 8 is arranged so that its vertical position can be adjusted. That is, the amount of molten metal supplied can be controlled by adjusting the gap between the upper end surface of the inner nozzle 1 and the lower end surface of the stopper 11.

The lower part of the inner nozzle 1 is inserted into the upper opening 2a of the flat outer nozzle 2 of the present invention, and the upper end surface of the upper opening is the heat-resistant paste 12 on the outer surface of the outer skin 9 of the tundish. Is abutted through the flat outer nozzle 2
Is a support 13 and a movable support 14 fixed to the support.
And the bolts and nuts 15 that fix them
Fixed.

After the tundish 8 and the flat outer nozzle 2 are brought into contact with each other in this manner, the lower portion of the flat outer nozzle 2 and the porous refractory 4 are preheated by the electric heating electrode 7 and positioned with respect to the moving mold. , The stopper 11 is raised to form a predetermined gap between the lower end surface of this stopper and the upper end surface of the inner nozzle 1, and the molten metal is supplied from the tundish 8 to the flat outer nozzle 2 through the inner nozzle 1 to form a multi-layered structure. The flat outer nozzle 2 is filled with the molten metal by the action of the mesh body 3 and is rectified by the porous refractory 4, and the molten metal is densely continuous between the tundish 8, the inner nozzle 1, and the flat outer nozzle 2, It is supplied with a uniform outflow distribution into the moving mold from the slit-shaped nozzle hole 5 below the flat nozzle, and continuous casting is started. After the shift to the steady operation, the position of the stopper 11 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.

When the outer nozzle 2 of the present invention is used, a multi-layer mesh body 3 and a porous refractory material in which a large number of through holes 4a are formed so that the molten metal outflow distribution from the slit-shaped nozzle holes 5 becomes uniform. By the action of 4, the molten metal can be supplied from the slit-shaped nozzle holes 5 into the moving mold with a uniform outflow distribution, the fluctuation of the meniscus position is suppressed, and the continuous casting operation is stabilized, so that a homogeneous thin cast piece can be stabilized. Can be cast into.

The present invention is not limited to the above-described embodiment, but the structure can be appropriately changed within a range satisfying the structures of claims 1 to 6.

[0034]

[Experimental Example] The flat outer nozzle of the present invention shown in FIG. 1 was attached as shown in FIG.
0 mm slab was continuously cast at a casting speed of 2.5 m / min.
Table 1 shows the specifications of the flow control refractory (filter) for the present invention and the conventional flat outer nozzle used in this experimental example.

[0035]

[Table 1]

As shown in FIG. 5, in continuous casting using the flat outer nozzle of the present invention, the distribution of the molten metal outflow amount from the slit-shaped nozzle holes of the flat outer nozzle to the moving mold is
Almost uniform in the axial direction of the cooling drum for a long time, the meniscus position was extremely stable, and no wrinkles were observed in the obtained slab.

On the other hand, in the case of the conventional example, the distribution of the outflow amount of the molten metal is large at the central portion of the porous refractory material (filter) and is small at the side end portions thereof. The meniscus position inside is high in the center of the filter,
It was low on the side edges, and wrinkles were observed in the obtained slab.

Further, in the present invention, since the through holes of the rectifying refractory material (filter) are linear and have a large hole diameter, the progress of clogging is extremely slow and continuous casting of about 600 tons can be continued. In the case of the conventional example, since the through holes of the filter are minute and are formed in a labyrinth,
Due to the rapid progress of clogging, continuous operation of about 10 tons forced the suspension of operations.

Even when the filter of the present invention is used for continuous casting of aluminum-killed steel in which a large amount of alumina is formed, the progress of clogging is slow, and continuous casting of several hundred tons is possible. However, in the case of the conventional example, since it becomes unusable in an extremely short time, it is difficult to put it into practical use.

[0040]

In the present invention, since the rectifying refractory (filter) obtained by forming a large number of through holes by, for example, drilling the relatively inexpensive refractory obtained by a very general manufacturing method is used. The through holes of the rectifying refractory (filter) can be formed easily with high accuracy and at low cost.

Further, by changing the combination of the mesh-like body and the through-holes of the straightening refractory material obtained as described above, the hole diameter (2 to 30 mm), the number, and the hole shape (flow resistance), the slit nozzle is changed. It is possible to rectify the molten metal supplied to the moving mold through the holes, remove inclusions and finely control the amount and flow rate of the molten metal.For example, the hole area ratio of the through holes in each part of the rectifying refractory or the through hole By selecting the flow resistance and making the outflow distribution of the molten metal from the slit nozzle holes uniform, the fluctuation of the meniscus position is reduced, the continuous casting is stabilized, and the homogenization of the slab is facilitated. Can be expected.

Further, since the through holes of the rectifying refractory material are formed large and linearly, and the temperature of the molten metal can be maintained uniform by heating with the current-carrying electrode, aluminum-killed steel that produces a large amount of Al ₂ O _{3 and the} like. With regard to steel types such as the above, since the adhesion and growth of these products to the filter is small, the filter is unlikely to be clogged and stable continuous casting is possible for a long time.

[Brief description of drawings]

1A and 1B are explanatory views showing an embodiment of a flat outer nozzle of the present invention, FIG. 1A is a partial sectional front view, and FIG. 1B is a partial sectional side view of FIG. 1A.

2A and 2B are explanatory views showing an example of a porous refractory material in an embodiment of a flat outer nozzle of the present invention, in which FIG. 2A is a partial sectional front view and FIG. 2B is a plan explanatory view.

FIG. 3 is an explanatory cross-sectional view showing Example 4 of a through hole of a porous refractory material (filter) used in the flat outer nozzle of the present invention.

FIG. 4 is a partial sectional front view showing an example of mounting the flat outer nozzle of the present invention.

FIG. 5 is a graph for explaining the effect of the experimental example of the present invention.

FIG. 6 is an elevational explanatory view showing an example of a twin-drum type continuous casting apparatus using the flat outer nozzle of the present invention.

7A and 7B are explanatory views showing an example of a conventional outer nozzle, in which FIG. 7A is a partially sectional front explanatory view, and FIG. 7B is a side explanatory view of FIG. 7A.

[Explanation of Codes] 1 inner nozzle 1a nozzle hole 2 flat outer nozzle 2a upper opening part 3 reticulate body 4 straightening (porous) refractory material 4a, 4b, 4c, 4d through hole 5 slit nozzle hole 6 degassing hole 7 energizing heating electrode 8 Tundish 9 Outer skin Iron skin 10 Fireproof block 11 Stopper 12 Heat-resistant paste 13 Support 14 Movable support 15 Bolts / nuts a Inner nozzle b Outer nozzle c Cast piece f Porous refractory d Meltable metal member e Molten metal p Hot water pool Ra, Rb: Cooling drum Sa, Sb: Side weir o Slit nozzle hole

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[Procedure amendment]

[Submission date] September 8, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 6

[Correction method] Change

[Correction content]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukio Inoue 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works Service Center Kurosaki Ceramics Co., Ltd. Kimitsu Branch Office (72) Inventor Yasushi Tsutsui 20-1 Shintomi-shi, Nippon Steel Co., Ltd. (72) Inventor Hideki Oka 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Hikari-shi, Nippon Steel Co., Ltd. (72) Takashi Arai, Hikaru Yamaguchi Prefecture 3434 Shimada, Oita-shi, Nippon Steel Corporation Hikari Steel Works

Claims (6)

[Claims] 1. A flat outer nozzle for twin-drum type continuous casting having an inner nozzle insertion hole in the upper portion and a slit nozzle in the lower end portion, and a rectifying refractory material having a large number of through holes is arranged at the bottom portion thereof. At the same time, a reticulated body is disposed on the refractory, the upper space of the reticulated body is communicated with the slit-shaped nozzle hole, and the side wall portion is provided with a current-carrying heating electrode. Flat outer nozzle for continuous casting. 2. The rectifying refractory material according to claim 1,
₂ O ₃ , MgO, CaO, SiO ₂ , ZrO ₂ , Si
A flat outer nozzle for twin-drum continuous casting, characterized by being formed of a refractory material composed of a single component of C, C, BN or a composite component thereof. 3. The twin-drum type continuous casting according to claim 1, wherein the rectifying refractory has a through hole having a diameter of 2 to 30 mm and the rectifying refractory has a hole area ratio of 10 to 30%. Flat outer nozzle. 4. The flat outer nozzle for twin-drum type continuous casting according to claim 4, wherein the hole area ratio in the rectifying refractory material is small in the central portion and large in both side portions. 5. A twin-drum type flat outer nozzle for continuous casting according to claim 1, wherein a flow resistance portion is formed in a through hole of the rectifying refractory material. 6. The flat outer nozzle for twin-drum type continuous casting according to claim 4, wherein the flow resistance in the through hole of the rectifying refractory is large in the central portion and small in both sides thereof.