JP2016209909A - Dipping nozzle for strip casting apparatus and strip casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dipping nozzle which maintains a scum handling function and has a low-cost and simple structure capable of manufacturing uniform products and a strip casting apparatus using the dipping nozzle.MEANS FOR SOLVING THE PROBLEM: A dipping nozzle for a strip casting apparatus comprises a hollow straight nozzle arranged in a horizontal direction and a hollow straight tube projecting in a vertical direction from the longitudinal center part of the hollow straight nozzle, has a roll-directional discharge opening in the nozzle longitudinal surface of the hollow straight nozzle arranged in a horizontal direction, and a side-weir-directional discharge opening in the nozzle width-directional surface of the hollow straight nozzle arranged in a horizontal direction, and has the relation of 0.1≤h/H between the height h from the lower end of a nozzle inner face of the roll-directional discharge opening and the side-weir-directional discharge opening and the height H of the nozzle inner face.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for continuously casting a thin slab such as aluminum or iron using a twin roll casting apparatus.

  The twin-roll casting device is a method in which a solidified shell is formed on the surface of a moving casting cooling roll by guiding a high-temperature molten metal between a pair of horizontal casting cooling rolls rotating in opposite directions, and the solidification is performed. It is an apparatus for taking out the shell as a thin cast piece from the roll gap outlet.

A conventional twin roll casting apparatus will be described in detail with reference to FIG.
FIG. 5 is a view for explaining a conventional strip casting apparatus equipped with a pouring nozzle for a strip casting apparatus.
In FIG. 5, 100 is a conventional immersion nozzle, 21 is a molten metal, 22 is a solidified shell, 23 is a thin cast piece, 3 is a tundish, 4 is a side weir, 5 is a scum weir, 6 is a cooling roll for casting, 8 Is a bender roll, and 9 is a twin roll casting apparatus.
The molten metal 21 is guided between the casting chill roll 6 through the conventional immersion nozzle 100 attached to the tundish 3 and the lower part of the tundish 3 to form the solidified shell 22 and then the thin cast slab. 23.

An outline of a molten metal injection method and apparatus in the twin roll casting method will be described.
As a simple device, there is an immersion nozzle that injects molten metal vertically downward (hereinafter referred to as “vertical downward injection immersion nozzle”).
However, when a vertically downward injection immersion nozzle is used, the solidified shell is thinned at the center of the slab width due to direct injection of the molten metal to the solidified shell solidified on the roll surface, and the molten metal is formed on the side weir side. As the temperature is lowered, the solidified shell becomes thick, the solidification uniformity of the entire slab deteriorates, and the slab surface breaks due to non-uniform solidification.

Non-Patent Document 1 discloses a two discharge port immersion nozzle (hereinafter referred to as a “side weir direction injection immersion nozzle”) that injects in the direction of the side weir.
However, when the side weir direction injection immersion nozzle is used, there are the following three problems.

First, the formation of the metal is suppressed by supplying heat from the molten metal to the side weir, but conversely, the solidified shell at the end of the slab becomes thin.
Second, the molten metal flows from the side weir side toward the center of the roll width, the thickness of the solidified shell at the center of the width increases, and solidification becomes uneven throughout.
Thirdly, a film in which non-metallic inclusions such as iron oxide and alumina contained in the molten metal, non-metallic oxides due to oxidation of metal elements on the surface of the molten metal during twin roll casting, etc. float on the surface of the molten metal (hereinafter, “ Scum ”), which accumulates in the center of the width, penetrates between the solidified shell and the roll, and becomes a heat removal resistance during solidification, thereby causing surface defects such as solidification delay in the center of the width and slab surface cracks. It is a problem of generating.

In Patent Document 1, in order to solve these three problems, a wide immersion nozzle (hereinafter, referred to as “roll direction injection wide immersion nozzle”) that injects in the direction of the cooling roll for casting (hereinafter referred to as “roll direction”). ) Is used.
The molten metal injected by the wide immersion nozzle in the roll direction flows from the center of the roll surface to the side weir, and after colliding with the side weir, turns around to the nozzle in the center of the pool to float the scum floating on the surface. And away from the solidification start portion between the roll and the roll to suppress the above defects.
However, if the injected molten metal causes large undulations on the molten metal surface, the solidification start point varies in the width direction, resulting in non-uniform solidification and cracking. Take measures such as using a thin slit shape.

  In Patent Document 2, when a roll direction injection wide immersion nozzle is used, a refractory weir (hereinafter referred to as “scum weir”) installed in parallel to the roll width direction is used, A method for adjusting the hot water flow between the scum weirs and promoting the accumulation of scum on the side of the nozzle at the center of the pool is disclosed.

However, the conventional immersion nozzle for a strip casting apparatus as disclosed in Patent Documents 1 and 2 has the following problems.
Hereinafter, the problem of the conventional immersion nozzle for a strip casting apparatus will be described with reference to FIG.
FIG. 3 is a diagram for explaining a conventional immersion nozzle for a strip casting apparatus.
A conventional immersion nozzle structure for a strip casting apparatus includes an inner nozzle 101 from a tundish and an outer nozzle 102 that surrounds the inner nozzle 101 and extends downward in parallel to the roll.
Furthermore, in order to distribute an even molten metal flow to the discharge port 105 that extends in the casting width direction provided at the lower part of the outer nozzle 101, a complex structure such as mounting a refractory material of the porous body 103 inside is adopted. .
Therefore, the conventional immersion nozzle for the strip casting apparatus is heavy and has the following two problems.

The first problem is that a conventional immersion nozzle for a strip casting apparatus is difficult to handle and requires introduction of a robot or the like for quick installation, and is expensive.
Secondly, the bare metal that grows in the contact portion near the roll of the side weir is occasionally peeled off and caught in the molten metal pool, sandwiched between the solidified shells and taken into the slab, and as a result, only the end of the slab is cast. The thickness of the piece increases instantaneously, and the unsolidified part at the center of the width is pulled out below the roll as it is, forming a red-hot part (hereinafter referred to as “hot band”), and the slab breaks at that part. However, the problem is that the slab thickness is extremely uneven and the product does not become a product.
When the second problem occurs, it is known that the fluctuation of the hot water level is large.

FIG. 4 illustrates the state of the molten metal surface when the casting apparatus using the conventional flat-shaped strip casting apparatus immersion nozzle shown in FIG. 3 is used.
FIG. 4A is a diagram illustrating a cross section of a strip casting apparatus equipped with a conventional immersion nozzle for a strip casting apparatus.
FIG.4 (b) is the figure which drawn the molten metal surface level in the strip casting apparatus provided with the conventional immersion nozzle for strip casting apparatuses.
In FIG. 4, 100 is a conventional immersion nozzle, 4 is a side weir, 7 is a scum accumulation location, 105 is a discharge port, and arrows indicate the flow of molten metal.

The cause of the large fluctuation of the hot water level will be described.
When the conventional shape nozzle as shown in FIG. 3 is examined by a simulation or the like, the molten metal flowing out from the discharge port 105 shown in FIG. In the direction of No. 7, a vortex is formed in the vicinity of the scum accumulation point, so that the molten metal flow is biased, and the fluctuation of the molten metal surface level becomes large. As a result, as shown in FIG. 4B, the fluctuation of the hot water level becomes large.
Therefore, it has not been considered to perform strip casting using the conventional flat-shaped immersion nozzle for a strip casting apparatus shown in FIG.

  Patent Document 3 discloses a wide thin plate continuous casting apparatus in which an immersion portion of a nozzle is an inverted T shape.

  In Patent Document 4, for the purpose of enabling a metal to flow in a mold in a more stable and more uniform state than a conventional immersion nozzle used in a continuous casting method of metallurgical products, a tubular first portion, Combining the hollow second part in an inverted T shape, one end of the first part communicates with a container containing liquid metal, the other end opens inside the second part, and at least the interior space of the second part 1 part is a nozzle for introducing a liquid metal into a continuous casting mold of metal of the type which is oriented in a direction substantially perpendicular to the first part and has at least one opening opened at both ends in the casting space of the mold. Having an obstacle located in the passage of the liquid metal inside or on the extension of the first part, the obstacle having a part with at least one hole for diverting the metal from the preferred track inside the nozzle Features It discloses a nozzle for.

However, in the inverted T-shaped immersion nozzles disclosed in Patent Documents 3 and 4, when the molten metal falls inside the vertical pipe, the flow is condensed and thinned, and the molten metal flow is staggered. It is easy to happen. Therefore, at the bottom of the inverted T-shaped nozzle, a pulsating flow or a drift is generated in the flow of the branched flow molten metal, and the flow of the molten metal discharged from the nozzle is biased. Furthermore, vortices are generated in the molten metal flow, increasing the instability of the nozzle discharge flow.
Therefore, there is a problem that cracks, wrinkles, and the like are likely to occur in the manufactured cast plate.

  Furthermore, in the inverted T-shaped immersion nozzle disclosed in Patent Document 4, the flow rate is reduced by disposing a filter-like porous body at the lower end of the vertical tube in order to suppress the fluctuation of the flow in the vertical tube, Since the discharge flow is stabilized by filling the inside of the vertical pipe with molten metal, the discharge flow may be caused by the possibility of a decrease in productivity due to clogging of the porous material or the porous material not changing uniformly over time. There is a concern that the bias and instability of the will not be resolved.

Japanese Patent Laid-Open No. 06-126395 Japanese Patent Laid-Open No. 08-164448 JP 60-021171 A JP 09-108794 A

“Mathematical and physical modeling of steel flow and solidification in twin-roll / horizontal belt thin-strip casting machine”, R.I.L.Guthrie and R.P.Tavares, Applied Mathematical Modeling 22 (1998) pp851-872

  An object of the present invention is to provide an immersion nozzle having an inexpensive and simple structure capable of maintaining a scum handling function and producing a uniform product, and a strip casting apparatus using the immersion nozzle.

  The inventors have conducted intensive research and development to realize an immersion nozzle having an inexpensive and simple structure that can maintain a scum handling function and can produce a uniform product, and `` If a nozzle with a simple structure is used, The molten metal supplied from the tundish is supplied by a straight pipe up to just above the molten pool, and combined with a straight nozzle having a sufficient length with respect to the casting width in the lateral direction, that is, the direction parallel to the roll axis, It is only necessary to provide slits or a plurality of discharge ports in the lateral nozzle and perform injection similar to that of a complex nozzle. "

However, in the case of performing this simple combination, the inventors do not fill the nozzle with molten metal, and the injection flow from the center of the width becomes strong, and the symmetry in the width direction is lost and the mold is lost. We faced the problem that it was difficult to create a uniform flow from the discharge port, such as the fluctuation of the hot water level inside.
Moreover, even if the inside of the nozzle was filled with molten metal, the flow discharged from the nozzle was poor in uniformity, and hot bands and cracks were often generated in the slab, and the yield of the slab was reduced. .

This is a period until the inside of the nozzle is filled at the initial stage of injection, or even after the inside of the nozzle is filled with molten metal. This is because it becomes uniform. As a result, a slab hot band or the like is generated.
Here, the molten metal pool is a portion of the molten metal pool between the rolls, and has the same function as the mold in the continuous casting method.

As a result of earnest research and development, including the hydrodynamic simulation of the behavior of the molten metal in the nozzle, the inventors have found that the straight nozzle has a side weir direction discharge port (hereinafter referred to as “first discharge port” or “side weir”). And a roll direction discharge port (hereinafter referred to as a “second discharge port” or a “roll direction discharge port”), and all the discharge ports are substantially in a horizontal plane. As a result, it was found that vortex flow formed in the vicinity of the scum accumulation place can be suppressed when the conventional shape nozzle as shown in FIG. 3 is used. The roll direction may be referred to as “scum weir direction”.
Furthermore, it has been found that by using a strip casting apparatus immersion nozzle having a roll direction discharge port and a side weir direction discharge port in combination, the injection flow rate into the casting space can be optimized and the solidification can be made uniform.

  Further, the position h from the lower end of the nozzle inner surface and the height H of the inner surface of the nozzle are determined in advance at the lower end position of the side dam direction discharge port which is the first discharge port and the second discharge port. When the injection starts inside the nozzle, the lower part of the nozzle horizontal portion is first filled with molten metal, and then the molten metal is discharged while the molten metal surface in the nozzle rises as a whole. After that, the inside of the nozzle was completely filled with the molten metal, and it was found that the nozzle was discharged in the roll direction in a state of being nearly uniform from the discharge port.

In addition, when the area of the side dam direction discharge port as the first discharge port and the roll direction discharge port as the second discharge port has a predetermined relationship, the effect of suppressing the scum entrainment phenomenon is improved. I got the knowledge to do.
The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) A hollow straight nozzle arranged in a horizontal direction, and a hollow straight pipe projecting in a vertical direction from a longitudinal central portion of the hollow straight nozzle,
A width direction surface of the hollow straight nozzle arranged in the horizontal direction (hereinafter referred to as “nozzle width direction surface”) has a first discharge port,
The longitudinal surface of the hollow straight nozzle arranged in the horizontal direction (hereinafter referred to as “nozzle longitudinal surface”) has a second discharge port,
Between the height h from the nozzle inner surface lower end of the first discharge port and the second discharge port and the height H of the nozzle inner surface,
0.1 ≦ h / H (Formula 1)
An immersion nozzle for a strip casting apparatus, characterized in that:

(2) at least one or more the sum of the cross-sectional area of the first discharge port and S _1,
At least one or more the sum of the cross-sectional area of the second outlet port and S _2,
0.1 ≦ S ₁ / (S ₁ + S ₂ ) ≦ 0.3 (Formula 2)
The immersion nozzle for a strip casting apparatus according to (1), wherein:

(3) A strip casting apparatus having the immersion nozzle for a strip casting apparatus according to (1) or (2).

  The immersion nozzle for the strip casting apparatus of the present invention is an immersion nozzle having an inexpensive and simple structure capable of producing a uniform product while maintaining the scum handling function. By using the immersion nozzle for the strip casting apparatus, the scum There is a remarkable effect that an inexpensive strip casting capable of maintaining a handling function and producing a uniform product can be realized.

It is a figure explaining the immersion nozzle for strip casting apparatuses of this invention. Fig.1 (a) is the immersion nozzle for strip casting apparatuses of this invention seen from the roll direction, and AA sectional drawing of Fig.1 (a) is FIG.1 (b). It is a figure explaining the mode of the hot_water | molten_metal surface when using the immersion nozzle for strip casting apparatuses of this invention. FIG. 2 (a) is a drawing depicting a cross section of a strip casting apparatus equipped with an immersion nozzle for a strip casting apparatus of the present invention. FIG.2 (b) is the figure which drawn the hot_water | molten_metal surface level in the strip casting apparatus provided with the immersion nozzle for strip casting apparatuses of this invention. It is a figure explaining the conventional immersion nozzle for strip casting apparatuses. FIG. 3B is a sectional view taken along the line BB in FIG. It is a figure explaining the mode of a molten metal surface when the conventional immersion nozzle for strip casting apparatuses is used. FIG. 4A is a diagram illustrating a cross section of a strip casting apparatus equipped with a conventional immersion nozzle for a strip casting apparatus. FIG.4 (b) is the figure which drawn the molten metal surface level in the strip casting apparatus provided with the conventional immersion nozzle for strip casting apparatuses. It is a figure explaining the mode of the molten metal surface of the strip casting apparatus using the conventional immersion nozzle for strip casting apparatuses.

(First embodiment)
The first embodiment of the present invention is an immersion nozzle for a strip casting apparatus.
The immersion nozzle for a strip casting apparatus according to the present invention will be described with reference to FIG.
FIG. 1 is a view for explaining an immersion nozzle for a strip casting apparatus according to the present invention.
Fig.1 (a) is a figure explaining the immersion nozzle for strip casting apparatuses of this invention seen from the roll direction. FIG.1 (b) is a figure explaining the immersion nozzle for strip casting apparatuses of this invention seen from the side dam direction.
In FIG. 1, 1 is an immersion nozzle for a strip casting apparatus, 11 is a height h from the lower end of the nozzle inner surface of the discharge port, 12 is a height H of the inner surface of the nozzle, 13 is a roll direction discharge port (second discharge port), Reference numeral 14 denotes a side weir direction discharge port (first discharge port). As the molten metal, molten steel is used.
As shown to Fig.1 (a), the immersion nozzle for strip casting apparatuses of this invention is the hollow straight nozzle arrange | positioned in the horizontal direction, and the hollow straight which protrudes toward a perpendicular direction from the longitudinal direction center part of the said hollow straight nozzle. With a tube. Such a shape may be referred to as an inverted T shape.
As shown in FIG. 1 (a), the nozzle longitudinal direction surface of the hollow straight nozzle arranged in the horizontal direction has a roll direction discharge port 13 on the nozzle width direction surface of the hollow straight nozzle arranged in the horizontal direction. Has a side weir direction outlet 14.

[Lower position of all discharge ports]
The following relationship is satisfied for all of the roll direction discharge ports 13 (second discharge ports) and the side weir direction discharge ports 14 (first discharge ports) (hereinafter referred to as “all discharge ports”).
In FIG. 1A, 11 is the height h from the lower end of the inner surface of the nozzle of all the discharge ports, 12 is the height H of the inner surface of the nozzle, and between these h and H,
0.1 ≦ h / H (Formula 1)
Have the relationship.
This is because if the lower end of the discharge port is too low, the molten metal supplied from the center in the nozzle width direction is less likely to be dispersed, and it is easier to discharge from the discharge port near the center of the width to the pool. However, the molten metal supplied from the center of the nozzle width spreads in the nozzle width direction through the nozzle inner bottom and flows into the nozzle by arranging the discharge port slightly above the nozzle inner surface bottom. This is because the water is dispersed and discharged from each discharge port equally. h / H is 0.1 or more, more preferably 0.125 or more. On the other hand, when h / H is 0.5 or more, the discharge flow becomes unstable and the effect is reduced.

  Furthermore, it is important that the lower end position of each discharge port is at the same height as the position of the lower end of the nozzle in order to stabilize the discharge flow at the beginning of molten metal injection. However, there may be a difference in height at the lower end position of each discharge port due to the occurrence of an error during manufacture. According to a 1/1 scale water model experiment or the like, it has been found that these height differences do not cause a problem if the standard deviation divided by the average value of the height h is within 0.5.

  The height H of the inner surface of the nozzle matches the inner diameter when the nozzle is a cylinder. In order to maintain the uniformity of the molten metal flow at an average casting speed of 30 m / min to 300 m / min, H is preferably 10 mm to 50 mm.

According to the 1/1 scale water model experiment, by imposing such a condition on the lower end position of the discharge port, the flow spreads in the space below the discharge port of the nozzle, and the pressure uniformity in the space is It was found that the fluctuation of the molten metal flow in the vertical pipe was absorbed, and the deviation of the discharge flow was suppressed. Furthermore, when only the nozzle end horizontal discharge port is provided, or the nozzle end horizontal discharge port is provided, and the discharge is vertically suppressed at the nozzle bottom, the drift can be significantly suppressed. I understood.
Further, the shape of each discharge port is not particularly limited, but the processing cost can be reduced if they are the same shape.

[Discharge port cross-sectional area ratio]
The sum of the cross-sectional area of at least one side weirs way discharge port (first discharge port) and S _1, the sum of the cross-sectional area of at least one roll direction discharge port (second discharge port) Is S ₂ and
0.1 ≦ S ₁ / (S ₁ + S ₂ ) ≦ 0.3 (Formula 2)
Have a relationship.
Here, the lower limit of 0.1 in (Equation 2) is intended not to inhibit the solidification of the slab and to suppress the formation of the metal on the side weir side. Since it was not possible, it was made 0.1 or more.

In addition, the upper limit of 0.3 in (Equation 2) is mainly intended to restrain the hot water ripple, and if it exceeds 0.3, the flow that collides with the side weir and reverses becomes stronger, and the discharge in the roll direction It interferes with the flow created by the flow, forms stagnation in the roll width direction, and scum easily enters between the roll and the shell. It has been found that the deviation in the width direction of the molten metal surface where cracking due to non-uniform solidification tends to occur is greater than ± 5 mm, that is, greater than 10 mm. Wherein in order to achieve an average casting speed stable is the total area _S 1 + _{S 2} of the discharge port ^is preferably 50 mm 2 500 mm ^2.

(Second Embodiment)
2nd Embodiment is a strip casting apparatus which has the immersion nozzle for strip casting apparatuses of this invention.
Specifically, in FIG. 5, it can be realized by using the strip casting apparatus immersion nozzle 1 of the present invention in place of the conventional strip casting apparatus immersion nozzle 100.

[Bath level]
The state of the molten metal surface when the strip casting apparatus using the immersion nozzle for strip casting apparatus of the present invention is used will be described with reference to FIG.
FIG. 2 (a) is a drawing depicting a cross section of a strip casting apparatus equipped with the immersion nozzle for strip casting apparatus of the present invention, and FIG. 2 (b) is equipped with the immersion nozzle for strip casting apparatus of the present invention. It is the figure on which the hot_water | molten_metal surface level in a strip casting apparatus was drawn.
In FIG. 2, 1 is an immersion nozzle of the present invention, 4 is a side weir, 7 is a scum accumulation location, 13 is a roll direction discharge port (second discharge port), and 14 is a side weir direction discharge port (first discharge port). ), Arrows indicate the flow of molten metal.
As depicted in FIG. 2A, the molten metal regularly flows out from the roll direction discharge port (second discharge port) 13 and the side weir direction discharge port (first discharge port) 14, and as a result, FIG. As shown in FIG. 2 (b), there is little fluctuation of the molten metal level, that is, a molten metal level difference.
From this, it can be confirmed that when the strip casting apparatus using the immersion nozzle for a strip casting apparatus of the present invention is used, the molten metal surface level is stabilized.

[Equipment used]
Steel thin-wall casting is performed using a twin roll casting apparatus using a casting cooling roll having a width of 400 mm and a diameter of 600 mm.

[Casting conditions]
A casting speed is set to 60 m / min, and a thin cast piece having a thickness of 3 mm is cast. The contact arc angle between the solidified shell and the roll was 45 degrees. As the molten metal, molten steel was used.

[Nozzle conditions]
The nozzle of the example of the present invention is an assembly in which a straight cylindrical refractory with an outer diameter of 60 mm, an inner diameter of 40 mm, and a length of 260 mm is closed and screwed to the lower end of a vertical straight refractory pipe having an outer diameter of 100 mm and an inner diameter of 70 mm. Used, the discharge port was machined in a horizontal direction on the surface in the longitudinal direction of the nozzle and the surface in the width direction of the nozzle.
The size of the discharge port in the roll direction is a square with a side of 10 mm, one discharge port for the side weir is provided at each end, a plurality of discharge ports in the roll direction are provided, and evaluation is performed by changing the total value of the cross-sectional areas. However, the total area (S ₁ + S ₂ ) of the discharge ports was uniformly 3600 mm ² .

As a nozzle of the comparative example, a conventional wide nozzle and a conventional inverted T-shaped nozzle were prepared. Conventional wide nozzles use a porous material to equalize the flow, and the discharge ports are in the roll direction. In the conventional inverted T-shaped nozzle, the end outlet in the scum weir direction is the same as that described above, and the nozzle in the horizontal direction (roll direction) on the nozzle bottom surface is not provided but the outlet is provided vertically downward.
However, the shape of one discharge port is the same as the horizontal direction of the longitudinal surface of the nozzle, and discharge ports are provided only in the vertical direction.

[Evaluation method]
If there is no occurrence of a hot band and the oil level difference is 12 [mm] or less, it is a pass (◯).
If no hot band is generated, the oil level difference is 12 [mm] or less, and there is no metal adhesion, it is an excellent pass (（).
If it is not passed (◯) or excellent (◎), it is a failure (x).

[Example of the present invention]
As an example of the present invention, No. 1 satisfying only (Equation 1). No. 6, 10, 11, No. 1 satisfying (Formula 1) and (Formula 2) 7, 8, 9, 12, 13, 14 were prepared.

[Comparative example]
A comparative example is No. which does not satisfy (Formula 1). 1-No. 5.
Comparative examples in the case of the conventional wide nozzle and the conventional inverted T-shaped nozzle are respectively No. 16, no. 17.

In this application, as shown in FIG. 2 (a), the flow discharged from the nozzle bottom in the direction of the side weir is reflected by the side weir, and the direction is changed by the discharge flow from the surface in the longitudinal direction of the nozzle. Interfering with the flow flowing in the direction, the generation of vortex flow is suppressed, the molten metal flow becomes uniform, and the occurrence of the molten metal level difference is suppressed.
No. 16, as described above, the flow shown in FIG. 4A is generated, so that a vortex flow is generated in the vicinity of the scum accumulation portion, so that a difference in molten metal level is likely to occur.
No. 17 is a conventional inverted T-shaped nozzle, and as described above, the difference in height of the flow becomes large, and both the adhesion of the metal and the hot band occur.

[Evaluation]
For the inventive examples, No. 1 satisfying only (Equation 1). Nos. 6, 10, 11, and 15 are acceptable (◯) and satisfy No. 1 satisfying (Equation 1) and (Equation 2). 7, 8, 9, 12, 13, and 14 were excellent passes (◎).
However, No. which is a comparative example. 1-5 and no. 16 and 17 were disqualified (x).
No. In the case of 16 comparative examples, the difference in the molten metal surface was 10 mm, but the adhesion of the metal base occurred and the generation of hot bands was observed occasionally.
No. In Comparative Example 17, the difference in hot water level was 18 mm, and both metal adhesion and hot band occurred.

Moreover, in order to investigate the influence when the lower end position of each discharge port varies, a sample having a difference in height at the lower end position of the discharge port was prepared. Table 2 shows the results of the difference in height difference.
No. Nozzle condition of the present invention example in 13 h = 5 mm (Equation 10)
h / H = 0.125 (Formula 11)
S ₁ / (S ₁ + S ₂ ) = 0.2 (Formula 12)
No. of Table 2 shows an example in which the difference in height difference is given while maintaining the average value of the nozzle lower end position height h at 5 mm. 18-23.
No. 18-No. 22 is an example of the present invention, and the value obtained by dividing the standard deviation of the height difference by the average value of the height is 0.5 or less.
No. 23 is a comparative example, and the value obtained by dividing the standard deviation of the height difference by the average value of the height is more than 0.5.

As in the example of the present invention, when the value obtained by dividing the standard deviation of the height difference by the average value of the height is 0.5 or less, no hot band is generated.
As in the comparative example, when the value obtained by dividing the standard deviation of the height difference by the average height value exceeds 0.5, a hot band is generated.
Generally, it does not depend much on the shape of the discharge port and the average value of the lower end of the nozzle, and if the value obtained by dividing the standard deviation of the height difference by the average value of the height is 0.5 or more, hot bands are likely to occur. It can be confirmed that there is a tendency.

  INDUSTRIAL APPLICABILITY The present invention can be used when continuously casting a thin slab such as aluminum or iron using a twin roll casting apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Submerged nozzle for strip casting apparatuses, 11 ... Height h from nozzle inner surface lower end of discharge port, 12 ... Height H of nozzle inner surface, 13 ... Roll direction discharge port (second discharge port), 14 ... Side weir Direction discharge port (first discharge port), 21 ... Molten metal, 22 ... Solidified shell, 23 ... Thin-walled slab, 3 ... Tundish, 4 ... Side weir, 5 ... Scum weir, 6 ... Cooling roll for casting, 7 DESCRIPTION OF SYMBOLS ... Scum accumulation part, 8 ... Bender roll, 9 ... Twin roll casting apparatus, 100 ... Conventional immersion nozzle, 101 ... Inner nozzle, 102 ... Outer nozzle, 103 ... Porous body, 104 ... Reinforcement material, 105 ... Discharge port.

Claims (3)

A hollow straight nozzle arranged in a horizontal direction, and a hollow straight pipe protruding in a vertical direction from a longitudinal central portion of the hollow straight nozzle,
On the surface in the width direction of the hollow straight nozzle arranged in the horizontal direction has a first discharge port,
The longitudinal surface of the hollow straight nozzle arranged in the horizontal direction has a second discharge port,
Between the height h from the nozzle inner surface lower end of the first discharge port and the second discharge port and the height H of the nozzle inner surface,
0.1 ≦ h / H (Formula 1)
An immersion nozzle for a strip casting apparatus, characterized in that: At least one or more the sum of the cross-sectional area of the first discharge port and S _1,
At least one or more the sum of the cross-sectional area of the second outlet port and S _2,
0.1 ≦ S ₁ / (S ₁ + S ₂ ) ≦ 0.3 (Formula 2)
The immersion nozzle for a strip casting apparatus according to claim 1, wherein:   The strip casting apparatus which has an immersion nozzle for strip casting apparatuses of Claim 1 or Claim 2.

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