JP2834657B2 - Tundish device capable of controlling molten metal flow - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses the flow of molten metal in a tundish, thereby increasing the residence time of the molten metal, thereby improving the floating effect of nonmetallic inclusions and the like in the tundish. The present invention relates to a tundish device capable of controlling the flow of molten metal.

[0002]

2. Description of the Related Art In continuous casting, molten metal (hereinafter, referred to as molten metal) is used.
Molten steel) is once poured from a ladle into an intermediate container called a tundish, and then poured into a mold from this tundish. One of the important roles of the tundish is to adjust the flow rate and flow rate of molten steel to the mold and to float and separate nonmetallic inclusions mixed in the molten steel.

[0003] That is, in the molten steel poured into the ladle,
Non-metallic inclusions such as various oxides as well as molten steel are mixed. If molten steel is poured into a mold in a state containing such impurities and casting is performed, defective properties or the like due to inclusions will occur, and it will be impossible to manufacture a slab conforming to product standards.

[0004] Since these impurities usually have a lower specific gravity than the molten steel, the impurities are floated and separated from the molten steel by retaining the molten steel in the tundish for a certain time, and only the clean molten steel is injected into the mold. Here, the floating separation of inclusions mixed in the molten steel in the tundish can be made better by increasing the residence time of the molten steel in the tundish, stirring the molten steel in the tundish, and the like.

[0005] For this reason, the ordinary tundish is designed so that the molten steel pouring position from the ladle to the tundish and the molten steel pouring position from the tundish to the mold are made as far as possible, so that the molten steel stays in the tundish. The time is configured to be long. In addition, a method of preventing inclusions from flowing into the mold by providing a weir in the tundish and promoting the floating of inclusions, and wiping the molten steel in the tundish with inert gas etc. to stir the molten steel It is also well known how to promote the flotation of inclusions.

Further, Japanese Patent Application Laid-Open No. 4-123851 discloses that an electromagnetic force is applied near the molten steel liquid surface of a tundish in a direction toward the outlet of the tundish to accelerate the flow rate of the molten steel, thereby reducing the presence of nonmetallic inclusions. On the other hand, a tundish for continuous casting which promotes levitation is disclosed in Japanese Patent Application Publication No. 3-501230, in which a magnetic field generator is provided outside the tundish so that the flow direction of the molten steel is substantially equal to the flow direction between the molten steel inlet and the outlet. Tundishes that suppress the flow of molten steel and extend the residence time by applying a magnetic field in orthogonal directions are disclosed, respectively.

However, in these various methods,
Insufficient levitation separation of inclusions from molten steel in the tundish is not possible, or expensive magnetic field generators are required, and inexpensive equipment can be used to better separate inclusions from molten steel. The advent of devices that can do so is desired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to suppress the flow of a molten metal in a tundish by using a plasma arc, so that the tundish is prevented. A molten metal flow controllable tundish device that improves the residence time of molten metal in the interior, improves the effect of removing non-metallic inclusions, and enables stable production of high-quality slabs with no defective properties Is to provide.

[0009]

In order to achieve the above object, the present invention provides a tundish having a molten metal injection part and a discharge part, and a flow of molten metal from the injection part to the discharge part of the tundish. A plurality of plasma torches, or a plasma torch and a counter electrode, and a plurality of plasma torches, or a driving power supply for the plasma torch installed between the plasma torch and the counter electrode, By arranging the plasma torch or the plasma torch and the counter electrode at a predetermined distance interval, by the magnetic field generated by the current flowing through the molten metal through the plasma arc generated between the plasma torch or the plasma torch and the counter electrode,
A tundish device capable of controlling molten metal flow, characterized in that a braking electromagnetic force is applied to the molten metal flowing in the tundish.

It is preferable that the position of the plasma torch is configured to follow the liquid level of the molten metal in the tundish.

[0011]

The molten metal flow controllable tundish apparatus of the present invention comprises a plasma torch, a counter electrode and a plurality of plasma torches arranged substantially horizontally in the flow direction of the molten metal, and a plasma torch directed toward molten steel in the tundish. By injecting the arc and using the magnetic field generated by the current flowing through the molten metal through the plasma arc, a braking electromagnetic force that suppresses the flow of the molten metal in the tundish is given, and the residence time of the molten metal in the tundish Can be extended to increase the floating separation effect of inclusions.

As is well known, by injecting a plasma arc, a current flows through the plasma arc from the positive electrode to the cathode of the plasma torch (or the plasma torch and the counter electrode). Here, in the tundish device of the present invention, a plasma torch or the like is arranged substantially horizontally in the flow direction of the molten metal, and a plasma arc is emitted toward the molten metal. In other words, in the present invention, the current flowing through the molten metal through the plasma arc is parallel to the flow of the molten metal (in the flow direction of the molten metal or in the opposite direction).
Becomes Therefore, a magnetic field is formed in the direction perpendicular to the flow of the molten metal by the current, and a braking electromagnetic force for suppressing the flow of the molten metal is generated by electromagnetic induction. That is, similarly to the so-called electromagnetic brake, the flow of the molten metal is suppressed, and inclusions mixed in the molten metal can be floated and separated well.

Here, if the distance between the flow of the molten metal and the plasma torch arranged in the horizontal direction is too small, the distance to be applied to the braking electromagnetic force in the flow of the molten metal is too short, and the distance between the molten metal and the torch is mixed. The floating inclusions cannot be floated and separated well.

On the other hand, if the interval between the plasma torches is too wide,
The path of the current flowing in the molten steel becomes unstable, and it is not possible to exert a good flow suppressing force. That is, as shown in FIG. 2, the main current that generates an electromagnetic force acting to suppress the flow of molten steel is a current a that flows linearly from the positive electrode to the negative electrode of the plasma torch. However, as the distance between the plasma torches increases, the currents b and c flowing in a curved manner between the torches increase, and the braking force decreases. Also, if the distance between the plasma torches is too wide, the impedance of the plasma system decreases, and if the input power is the same, the current flowing in the molten steel decreases, and the magnetic field generated in the molten steel also decreases. become weak.

In the tundish device of the present invention,
Plasma torches arranged horizontally with the flow of the molten metal are arranged at predetermined intervals, preferably 500 to 1000 mm, at which a braking electromagnetic force can be applied to the molten steel flow. Therefore, according to the tundish device of the present invention capable of controlling the flow of the molten metal, the residence time of the molten metal in the tundish can be appropriately lengthened, and the inclusions mixed in the molten metal can be floated and separated favorably. Thus, it is possible to inject only clean molten metal into the mold.

Further, the present invention suppresses the flow of the molten metal by injecting the plasma arc toward the molten metal. The plasma arc is very high temperature, and by using this to heat the molten metal in the tundish, secondary scouring, prevention of nozzle clogging, acceleration of inclusion removal, etc. can be measured. No. 3-2432
No. 54 and Japanese Patent Publication No. 4-52599. Therefore, according to the tundish device of the present invention capable of controlling the flow of molten metal, not only the floating separation of inclusions by controlling the flow of molten metal but also the effect of heating the molten metal in the tundish by the plasma arc can be obtained at the same time. It is possible to stably produce higher quality slabs. Moreover, since the result also serves as a heating facility, the facility is inexpensive as a result.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tundish apparatus capable of controlling the flow of a molten metal according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of a tundish device (hereinafter, referred to as a tundish device) of the present invention capable of controlling the flow of molten metal. In FIG. 1, (a) is b
FIG. 2 is a schematic plan sectional view taken along line -b, and FIG. 2 (b) is a schematic front sectional view taken along line aa.

In the tundish apparatus 10 shown in FIG. 1, a molten metal (hereinafter referred to as molten steel) 30 is a ladle 32.
Is supplied to the tundish 36 by a long nozzle 34 and injected into a mold 40 from an immersion nozzle 38 provided at an outlet of the tundish 36. Reference numeral 42 arranged below the mold 40 is a slab support roll. The tundish 36 is the main body 4
4 and a lid 46 for closing the upper surface of the main body 44, and a weir 4 for promoting the floating of nonmetallic inclusions and the like at the bottom.
8 are arranged.

Here, in the tundish apparatus 10 according to the present invention, the lid 46 is provided with the plasma torches 12 and 14 and the drive power source 20 for both plasma torches. The plasma torches 12 and 14 inject the plasma arcs 16 and 18 into the molten steel 30, respectively. In the tundish device 10 according to the present invention, both plasma torches are arranged along the flow direction of the molten steel 30.

The tundish device 10 of the present invention has the above configuration, that is, a plurality of plasma torches, or a plasma torch and a counter electrode are arranged horizontally in the flow direction of molten steel.
By having a configuration in which the plasma arc is injected into the molten steel 30, a current in the horizontal direction (that is, the flow direction or the opposite direction) to the flow of the molten steel is caused to flow into the molten steel by the plasma arcs 16 and 18, and the flow of the molten steel is caused by the current. A magnetic field is formed in a direction orthogonal to the magnetic field, and the electromagnetic brake effect is obtained by electromagnetic induction by this magnetic field and the flow of molten steel.
The flow of the molten steel 30 from the long nozzle 34 to the immersion nozzle 38 is suppressed. This operation will be described later in detail.

According to the present invention, the electromagnetic brake extends the residence time of the molten steel 30 in the tundish 36, improves the effect of reliably floating and separating inclusions mixed in the molten steel 30, and stably produces a high-quality slab. It is possible to manufacture. Moreover, since the plasma arcs 16 and 18 are injected toward the molten steel 30, the result also serves as a heating means for the molten steel 30 in the tundish 36.
As a result, effects such as secondary scouring, prevention of nozzle clogging, and acceleration of inclusion removal can be exhibited.

The plasma torches 12 and 14 used in the tundish device 10 of the present invention are not particularly limited, and any known plasma torch can be used.
The inside of the tundish 36 is of course an atmosphere corresponding to the plasma torches 12 and 14 (plasma arcs 16 and 18) to be used.

The drive power supply 20 may be either AC or DC. In the illustrated example, a direct current is used as an example to simplify the description. This will be described in detail later. The amount of electricity that the driving power supply 20 supplies to the plasma torches 12 and 14 may be appropriately determined depending on the type of the plasma torch and the like, and is not particularly limited. If the amount of power is high,
Naturally, a stronger electromagnetic braking effect can be obtained, but at a very high power, the plasma arcs 16 and 18 can be used.
Temperature becomes too high, which may adversely affect the molten steel 30.

In the tundish device 10 of the present invention, the plasma torch to be used is not limited to the two shown in the illustrated example, but may be a single plasma torch combined with a counter electrode, or if necessary. Three or more plasma torches may be used, or both may be used in combination.

Here, the tundish device 10 of the present invention is used.
In the above, it is necessary to arrange the plasma torches in a horizontal direction with respect to the flow of the molten steel and at an interval capable of applying a braking electromagnetic force to the flow of the molten steel. As described above, if the distance between the two plasma torches is too small, the distance to be applied to the braking electromagnetic force in the flow of the molten metal is too short, and it is not possible to float and separate the inclusions mixed in the molten metal satisfactorily. . On the other hand, if the distance between the two plasma torches is too wide, the path of the current flowing in the molten steel becomes unstable, as shown in FIG. If the input power is the same, the impedance becomes small, and the current flowing in the molten steel becomes small, and the magnetic field generated in the molten steel is also weakened.

Accordingly, the tundish device 10 of the present invention
In the above, it is necessary to arrange the plasma torches at intervals at which good braking electromagnetic force can be applied to the flow of molten steel. This interval varies depending on the size of the tundish 36, the output of the plasma torch, and the like, and cannot be determined unequivocally, but it is generally considered that an interval of about 500 to 1000 mm is preferable.

FIG. 3 shows the interval between the plasma torches and the amount of inclusions in the molten steel when the tundish device 10 is configured using EB (electron beam) as a plasma torch (naturally, a smaller amount has a better flow suppressing effect). The relationship is shown below.
In the example shown in FIG. 3, the plasma torch is a DC torch and the input power is 1.2 MW. As shown in FIG. 3, the inclusion in the molten steel is smallest when the plasma torch interval is about 700 mm, and the plasma torch interval is 500 to 10 mm.
When the distance is between 00 mm and 100 mm, the inclusion can have a good effect of removing inclusions of 0.8 mm ² / g or less.

The distance between the liquid surface of the molten steel 30 and the plasma torches 12 and 14 is not particularly limited.
14 and the characteristics of the desired plasma arcs 16 and 18, that is, the desired amount of current flowing through the molten steel 30, may be determined as appropriate. When the distance between the liquid surface of the molten steel 30 and the plasma torches 12 and 14 changes, the impedance changes and the characteristics of the plasma arcs 16 and 18 change. Therefore, the plasma torches 12 and 14
It is preferable to be configured to move up and down so as to keep the distance from the liquid level of the molten steel 30 constant.

Hereinafter, the operation of the tundish device 10 of the present invention will be described in detail. As described above, molten steel 30
Is supplied to the tundish 36 from the long nozzle 34 and injected into the mold 40 from the immersion nozzle 38. Therefore, the molten steel 30 in the tundish 36
Can be indicated by the arrow m as a large flow.

On the other hand, the plasma torches 12 and 14
The plasma torch 12 is disposed horizontally in the flow direction of the molten steel 30, that is, along the direction of the arrow m.
Is connected to the plus side, while the minus side is connected to the plasma torch 14. Plasma torch 12 from drive power supply 20
When power is supplied to and the plasma arcs 16 and 18 are injected, a current flows through the molten steel as indicated by an arrow n. Therefore, by this current flow,
A magnetic field that rotates clockwise in the direction of current flow, that is, a magnetic field indicated by an arrow o is formed.

Since this magnetic field is in a direction orthogonal to the flow of the molten steel 30 (arrow m), electromagnetic induction is generated by the magnetic field and the flow of the molten steel 30, and the electromagnetic force is applied in a direction to suppress the flow velocity of the molten steel 30. Force is generated. That is, the flow of the molten steel 30 is suppressed similarly to the electromagnetic brake. Therefore, in the tundish 36, the molten steel 30 is prevented from flowing at a high speed from the long nozzle 34 to the immersion nozzle 38, the residence time of the molten steel 30 in the tundish 36 is increased, and the floating separation of inclusions is performed. Can be performed well. In addition, the effect of heating the molten steel in the tundish 36 by the plasma arcs 16 and 18 can be obtained as described above.

In order to confirm the effects of the present invention, the present inventors conducted the following experiments. <Experimental Example> Continuous casting was performed using the tundish apparatus 10 of the present invention shown in FIG. In addition, the size of the tundish 36 (dimension on the inner wall) is 1.2 m × 3.0 m,
At a depth of 1.0 m, the distance from the long nozzle 34 to the immersion nozzle 38 is 2.0 m. The casting speed is 3
ton / min. The plasma torch was arranged at substantially the same position (interval: 0.6 m) as shown in FIG. The current supplied to the plasma torches 12 and 14 was 5000 A. As a result, the residence time of the molten steel 30 can be preferably extended as compared with the case where the tundish device 10 of the present invention is not used, and the inclusions in the cast continuous cast piece can be reduced by about 20%. Was completed.

The example described above is an example in which a DC power supply is used as the drive power supply 20. However, when an AC power supply is used as the power supply, only the direction of the magnetic field is reversed according to the frequency, and the molten steel 30 is not used. The traveling direction and the magnetic field are always orthogonal. Therefore, a good electromagnetic braking effect can be obtained as in the case of the DC power supply. When the AC power supply is used as the driving power supply for the plasma torch, if the frequency becomes too high, the current flows through the molten steel surface due to the skin effect, and the suppressing force of the molten steel flow does not reach the bottom of the tundish. Would. Therefore, when an AC power supply is used as the driving power supply for the plasma torch, it is preferable that the frequency be lower than the commercial frequency (50 or 60 Hz).

There is no particular limitation on the type of tundish that can be used in the present invention.
A two-tank tundish with a swirl tank and a floating tank, etc.
Various known tundishes are available.

Although the tundish apparatus capable of controlling the flow of molten metal according to the present invention has been described in detail, the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, changes may be made.

[0037]

As described above in detail, according to the tundish apparatus of the present invention capable of controlling the flow of molten metal, the function of the electromagnetic brake is exhibited by utilizing the plasma arc.
By suppressing the flow of the molten steel in the tundish, the residence time of the molten steel can be appropriately lengthened. Therefore, it is possible to satisfactorily levitate and separate nonmetallic inclusions and the like mixed in the molten steel, and to inject only clean molten steel into the mold. In addition, since the plasma arc is injected toward the molten steel, the effect of heating the molten steel in the tundish by the plasma arc can be obtained at the same time, and a slab of higher quality can be stably manufactured. In addition, since the heating device also serves as a result, the equipment is inexpensive.

[Brief description of the drawings]

1 (a) and 1 (b) are schematic views of a tundish apparatus capable of controlling the flow of a molten metal according to the present invention, wherein (a)
Is a top sectional view, and (b) is a front sectional view.

FIG. 2 is a diagram for explaining the relationship between the interval between plasma torches and the flow of current in a tundish device capable of controlling molten metal flow according to the present invention.

FIG. 3 is a graph showing a relationship between an interval between plasma torches and an effect of removing inclusions in a tundish device capable of controlling molten metal flow according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tundish apparatus 10 12,14 Plasma torch 16,18 Plasma arc 20 Drive power supply 30 Molten steel 32 Ladle 34 Long nozzle 36 Tundish 38 Immersion nozzle 40 Mold 42 Slab support roll 44 Main body 46 Cover 48 Weir

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-15951 (JP, A) JP-A-4-89160 (JP, A) JP-A-3-124351 (JP, A) JP-A-61- 255750 (JP, A) JP-A-59-220264 (JP, A) JP-A-6-114511 (JP, A) JP-A-59-163062 (JP, A) JP-A-59-202144 (JP, A) JP-A-59-202142 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/10 B22D 41/015

Claims (2)

(57) [Claims] 1. A tundish having a molten metal injection part and a discharge part, and a plurality of plasma torches or plasma torches arranged horizontally in a flow direction of the molten metal from the injection part to the discharge part of the tundish. And a counter electrode, and a drive power supply for the plurality of plasma torches, or the plasma torch provided between the plasma torch and the counter electrode, and arranging the plurality of plasma torches or the plasma torch and the counter electrode at a predetermined distance. By applying a braking electromagnetic force to the molten metal flowing in the tundish by a magnetic field generated by a current flowing in the molten metal through a plasma arc generated between the plasma torch or between the plasma torch and the counter electrode. Tundish device capable of controlling molten metal flow. 2. The tundish apparatus according to claim 1, wherein the position of the plasma torch is configured to follow the liquid level of the molten metal in the tundish.