JPH05138302A - Method for preventing leakage of molten metal in twin roll strip continuous casting - Google Patents

Abstract

PURPOSE:To stably cast a cast strip having favorable shapes of the end parts and uniform width for a long time by preventing molten metal from invasion and leakage in a gap between side weirs pressed to the side surfaces of rolls and the side surfaces of the rolls in the twin roll strip continuous casting. CONSTITUTION:Ferromagnetic bodies 2a, 2b, 3a, 5b are arranged in each of the inner parts of the rolls 1a, 1b and the side weirs 5a, 5b, and DC magnetic fields are impressed between the rolls 1a, 1b and the side weirs 5a, 5b. As the other way, the ferromagnetic, bodies are arranged in the inner parts of the rolls 1a, 1b and by impressing the magnetic fields from the outsides of the side weirs, the magnetic fields are generated between the side weirs and the rolls 1a, 1b. By impressing DC current along drawing-out direction of the cast strip 10 from the rolls 1a, 1b, electromagnetic force is acted to the molten metal 9 between the rolls 1a, 1b to prevent the leakage of the molten metal from the gap between the side weirs 5a, 5b and the rolls 1a, 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin roll type continuous casting of thin plates for directly producing thin plate-shaped ingots from molten metal.

[0002]

In the twin-roll type thin plate continuous casting method, when molten metal is poured between two rolls rotating in opposite directions, the molten metal also flows in a direction parallel to the roll axis.
It flows out from both ends of the roll. To prevent this outflow,
Conventionally, a casting method has been known in which a side weir is pressed against the side surface of a rotating roll, for example, JP-A-60-1625.
No. 58 and Japanese Patent Application Laid-Open No. 61-144245, a method using vertically divided fixed side weirs,
JP-A-60-166146 and JP-A-60-170
There is a method using the vibrating side weir disclosed in Japanese Patent No. 559. As a casting method that does not use a side weir, a method in which a magnetic field is generated in the roll gap by bringing a magnet close to the roll surface and the molten metal between the rolls is held by the action of this magnetic field is disclosed in JP-A-1-266946. It is disclosed.

[0003]

In twin roll type thin plate continuous casting, it is important that the end shape of the slab is good and that the width is uniform. It is important to completely prevent the invasion of the molten metal and the accompanying leakage of the molten metal.

When the side weir is pressed against the side surface of the roll,
When molten metal enters the gap between the roll side surface and the side weir surface, cast burr is generated, and when the side weir surface is scraped by the cast burr, the molten metal flows out from the scraped gap or the slab is cast. Due to the occurrence of dripping on the surface, it becomes difficult to continuously cast a good slab, and long-time casting cannot be performed.

In the method in which a magnetic field is generated in the roll gap and the molten metal between the rolls is held by the action of the magnetic field without using side dams, when the depth of the molten metal between the rolls becomes deep, the molten metal is acted only by the action of the magnetic field. Can no longer be held, molten metal flows out from both ends of the roll, and it becomes difficult to continuously cast a thin plate cast piece having a good end shape.

When the end shape of the cast slab is defective and the width is not uniform, it is necessary to cut the end of the cast slab to make the width uniform in the process of commercialization, resulting in a decrease in yield and an increase in work processes. Becomes

The present invention solves the above-mentioned problems, stably manufactures a thin plate slab having a good end shape and a uniform width, and is capable of long-time casting of the slab, the molten metal in twin roll type thin plate continuous casting. To provide a leak prevention method.

[0008]

According to a first aspect of the present invention, molten metal is poured into a gap between a pair of rolls rotating in opposite directions, and the metal is solidified to produce a thin plate-shaped slab. In twin roll type thin plate continuous casting, when holding the molten metal between the rolls by pressing the side weir against the side face of the roll, a ferromagnetic material is installed inside the roll, and a side composed of refractory and ferromagnetic material. A direct current magnetic field is generated between the roll and the side weir using the weir, and a direct current is applied along the direction in which the thin plate slab comes out of the roll, so that the corner portion of the roll and the side weir This is a method for preventing leakage of molten metal in twin-roll type thin plate continuous casting, characterized in that electromagnetic force is applied to the molten metal to prevent leakage of molten metal from the gap between the side dam and the roll.

A second aspect of the present invention is a twin roll type continuous plate casting in which molten metal is poured into a gap between a pair of rolls rotating in opposite directions and the metal is solidified to produce a thin plate-shaped slab. In order to hold the molten metal between the rolls by pressing the side weir against the side of the roll, a ferromagnetic material is installed inside the roll, and a magnetic field is applied from the outside of the side weir made of refractory to the end of each roll. A magnetic field is generated between the roll and the side dam by applying, and by applying a direct current along the direction in which the thin plate slab comes out of the roll, a corner portion of the roll and the side dam is generated. This is a method for preventing leakage of molten metal in twin-roll type thin plate continuous casting, characterized in that electromagnetic force is applied to the molten metal to prevent leakage of molten metal from the gap between the side dam and the roll.

[0010]

1A and 1B show a method for preventing leakage of molten metal when a ferromagnetic material is installed inside the roll and inside the side dam and a magnetic field is generated between the roll and the side dam. 1A is a plan view and FIG. 1B is a sectional view taken along the line AA ′ in FIG. 1A.

As a method of applying a magnetic field to the roll gap, a method of installing a magnet inside each roll to generate a magnetic field in the roll gap, or a method in which the roll is made of a ferromagnetic material or a ferromagnetic material and a paramagnetic material is used. There is a method of generating a magnetic field in the roll gap by bringing a magnet installed outside the roll close to the ferromagnetic material of the roll, which has a composite structure composed of a non-magnetic material, and FIG. 1 shows the latter method. That is, roll 1
a and 1b have ferromagnetic bodies 2a, 3a and 2b, 3b at the ends of their respective rolls, and by bringing the magnetic poles of a permanent magnet or electromagnet close to these ferromagnetic bodies from the outside, A DC magnetic field can be generated in the gap between 2a and 2b and the gap between the ferromagnetic bodies 3a and 3b. When a magnetic field is generated in the gap between the rolls by these methods, the magnetic flux density becomes weaker as the gap between the rolls increases in any of the methods.Therefore, when the molten metal is poured between the rolls, the magnetic flux density increases toward the top of the molten metal. Becomes smaller.
Therefore, when a ferromagnetic material is installed on the side weir, a magnetic field is generated between the ferromagnetic material of the roll and the ferromagnetic material inside the side weir, and the magnetic flux density between the roll and the side weir should be extremely large. You can

Thus, a magnetic field is generated between the roll and the side dam, and as shown in FIG. 1 (b), a DC power source 12, electrodes 6a, 6b and a lower electrode 13 are used to form a thin plate in the molten metal. When a current is applied in the direction in which the slab comes out from between the rolls, an electromagnetic force toward the central portion in the axial direction of the roll acts on the molten metal by the action of the DC magnetic field and the DC current. Regarding the position of the electrode, it is preferable to immerse the electrode in the molten metal near the corner of the side weir and the roll surface as much as possible so that an electric current is caused to flow near the corner of the side weir and the roll surface. Also, in order to prevent the electric current from leaking to the other through the roll, for example, it is necessary to insulate the roll shaft and the bearing, or to coat the roll surface with an insulating material to generate electromagnetic force in the molten metal for safety. Needed from a point.

FIG. 2 schematically shows a method of holding the molten metal at the corners of the roll and the side dam by electromagnetic force. When a DC magnetic field with a magnetic flux density B is present in the molten metal at the corners of the roll and the side dam, a current J is applied to the molten metal.
By applying the magnetic field, an electromagnetic force F toward the central portion in the roll axis direction acts on the molten metal by the action of the magnetic field and the electric current.
Since the magnetic flux density becomes extremely large in the vicinity of the gap between the roll and the side weir due to the ferromagnetic bodies 16a and 16b of the side weir 5a, the electromagnetic force acting on the molten metal in the vicinity of the gap between the roll and the side weir becomes extremely strong. Leakage of molten metal from the roll gap is prevented.

Therefore, in FIG. 1 (b), a DC magnetic field and a DC current are applied to the roll gap so that the rolls 1a and 1b
When the molten metal 9 is poured between the rolls 1a and 1b through the pouring nozzle 8 by rotating in opposite directions, solidified shells of the molten metal are formed on the two roll surfaces, respectively, and these solidified shells are formed in the roll gap. Crimped, rolls 1a, 1b
The molten metal 9 does not leak from between the side dams 5a and 5b, and the slab 10 having a good end shape and a uniform width can be continuously manufactured.

FIG. 3 shows an example of a method in which ferromagnetic bodies 2a and 2b are installed inside rolls 1a and 1b, respectively, and a magnetic field is applied from the outside of the side weir. The method of installing the electromagnets 19a and 19b and applying the magnetic field generated from these electromagnets toward the ends of the rolls 1a and 1b will be described. Further, FIG. 4 shows C- of FIG.
It is sectional drawing of the position of C '. That is, as shown in FIG. 4, when magnetic fields B ′ are generated in two electromagnets and the electromagnets are brought close to the ferromagnetic material of each roll, the magnetic field B is generated in the molten metal existing near the corners of the roll and the side dam. Then, as described with reference to FIG. 1B, when a current is applied in the molten metal in the direction in which the thin plate slab 10 comes out from between the rolls, the action of the DC magnetic field and the DC current causes the molten metal to move in the axial direction of the roll. The electromagnetic force F toward the central part acts. Due to the action of this electromagnetic force, the molten metal does not enter the gaps 18a and 18b between the roll and the side dam, and leakage can be prevented.

The gaps 18a and 18b between the roll and the side weir in FIGS. 2 and 4 are drawn in an emphasized manner.
If the strength of the magnetic field generated between the roll and the side weir is sufficiently strong, the molten metal will not leak from the gap even if the roll and the side weir are completely placed in non-contact with casting. But,
It is more advantageous to lightly press the side weir against the side surface of the roll for casting in order to completely prevent leakage of molten metal. In this case, the gap between the roll and the side weir depends on the parallelism and roughness of the roll side surface and the side weir surface.
There is a gap of about 0.3 mm, and if the present invention is not applied, the molten metal penetrates into the gap as the depth of the molten metal becomes deeper. However, by applying the present invention, the gap between the roll and the side weir Molten metal does not invade and leakage can be completely prevented.

[0017]

【Example】

Example 1 An austenitic stainless steel casting experiment was conducted using the twin roll casting apparatus shown in FIG. Rolls 1a, 1b
Was used as the ferromagnetic materials 2a, 2b, 3a and 3b, and paramagnetic austenitic stainless steel was used as the other roll portions. As shown in FIG. 2, boron nitride was used as the refractory and iron was used as the ferromagnetic material for the side weirs 5a and 5b, and the side weirs 5a and 5b were lightly pressed against the side surfaces of the rolls 1a and 1b. By bringing the electrode of the electromagnet close to the ferromagnetic material of the roll, the gap between the rolls 1a and 1b and the roll 1
A magnetic field was generated in the gap between a and 1b and the side weirs 5a and 5b. Ferromagnetic materials 2a, 2b, 3a, 3 of the rolls 1a, 1b
The magnetic flux density of the magnetic field applied to b was changed from 0 to 2 tesla. On the other hand, as shown in FIGS. 1 (a) and 1 (b), ZrB ₂
The electrodes 6a, 6b, 7a, 7b made of was immersed in the molten metal 9 near the weirs 5a, 5b, and a direct current of 0 to 500 A was applied. The bearings of the rolls 1a and 1b were insulated so that the electric current did not leak through the rolls 1a and 1b. Rolls 1a and 1b have a diameter of 300 mm and a body length of 13
0 mm, the two ferromagnetic bodies 2a, 2b, 3a, 3b
The length in the roll axis direction is 40 mm, and the length of the paramagnetic material is 50 mm. As operating conditions, the roll rotation speed is 10 to 90 rpm, the molten metal 9 pouring flow rate is 0.3 to
Roll 1 with various changes within the range of 1.2 kg / sec
The pouring flow rate was adjusted so that the height of the molten metal 9 between a and 1b was constant at about 100 mm.

As a result of the experiment, if the strength of the magnetic field and the current applied to the molten metal 9 is not sufficiently strong, casting burrs are formed at the ends of the slab, and the rolls 1a, 1b and the side dams 5a, 5b are formed.
Although the molten metal 9 leaked from the gap of No. 1, when the strength of the magnetic field and the current was increased to some extent or more, the molten metal did not leak from the gap between the rolls 1a and 1b and the side dams 5a and 5b, and the thickness was about 1 to 1. With a thickness of 3 mm, a thin plate slab having a good end shape and a uniform width was obtained. Under these experimental conditions, the ferromagnetic materials 2a, 2b, 3a, 3 of the rolls 1a, 1b were
When the magnetic flux density of the magnetic field applied to b is 1 tesla, the side dam 5a,
It was possible to prevent the molten metal 9 from leaking from the gap between the roll 5a and the rolls 1a and 1b. As is clear from the results of this experiment, according to the present invention, it is possible to completely prevent the molten metal from entering and leaking between the roll and the side weir.

Embodiment 2 As shown in FIGS. 3 and 4, ferromagnetic materials 2a and 2b are installed inside rolls 1a and 1b, and a magnetic field is applied from the outside of a refractory side weir 20 by using electromagnets 19a and 19b. Was applied to generate a magnetic field between the rolls 1a and 1b and the side weir 20, and a direct current was applied in a direction in which the slab 10 exits from the rolls 1a and 1b. The experimental conditions other than the side weir 20 and the method of generating the magnetic field were the same as in Example 1.
It is as explained in. In this experiment, a side weir 20 made of boron nitride was lightly pressed against the side surfaces of the rolls 1a and 1b to form a coil for the electromagnets 19a and 19b with a diameter of 4 mm.
As shown in FIG. 4, electromagnets 19a, 19 are used as shown in FIG.
A magnetic field generated from b was applied toward the ends of the rolls 1a and 1b to generate a magnetic field between the rolls 1a and 1b and the side weir 20, and a casting experiment was performed. The electromagnets 19a, 1
In order to make the magnetic field generated from 9b stronger, ferromagnetic iron was installed in the coil. At this time, the electromagnets 19a, 19
The magnetic flux density of b was about 0.2 tesla. As a result of this experiment, if the electromagnetic force is not applied to the molten metal, a casting burr is formed at the end of the cast piece, or the rolls 1a, 1b and the side dam 20 are formed.
Although the molten metal leaked from the gap of, by applying a magnetic field from the outside of the side weir 20 and applying a direct current to the molten metal along the direction in which the slab comes out from between the rolls 1a and 1b, A thin plate slab having a thickness of about 1 to 3 mm, no burrs and a good end shape could be manufactured.

[0020]

EFFECTS OF THE INVENTION According to the present invention, it is possible to prevent molten metal from entering the gap between the roll and the side weir and preventing the leak from the gap, and it is possible to obtain a thin plate slab having a good end shape and a uniform width for a long time. Can be cast.

[Brief description of drawings]

FIG. 1 is a drawing showing a method for preventing molten metal from leaking when a ferromagnetic material is installed inside a roll and inside a side dam and a magnetic field is generated between the roll and the side dam. A plan view and (b) are sectional views taken along the line A-A 'in (a).

FIG. 2 is a sectional view taken along the line BB ′ in FIG. 1 (b).

FIG. 3 is a side view showing a method for preventing leakage of molten metal when a magnetic field is applied from the outside of the side dam toward the ferromagnetic material inside the roll.

FIG. 4 is a sectional view taken along the line CC ′ in FIG.

[Explanation of symbols]

 1a, 1b Roll 2a, 2b Ferromagnetic material 3a, 3b Ferromagnetic material 4a, 4b Roll shaft 5a, 5b Side dam 6a, 6b Electrode 7a, 7b Electrode 8 Pouring nozzle 9 Molten metal 10 Thin plate slab 11 Movement of slab Direction 12 DC power supply 13 Lower electrode 14 Electric wire 15 Direction of current flow 16a, 16b Ferromagnetic material 17 Refractory material 18a, 18b Gap 19a, 19b Electromagnet 20 Refractory side weir

Front Page Continuation (72) Inventor Yoshiyuki Uejima 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd.

Claims (2)

[Claims] 1. A twin-roll type thin plate continuous casting for producing a thin plate-shaped slab by pouring molten metal into a gap between a pair of rolls rotating in opposite directions and solidifying the molten metal. When holding the molten metal between the rolls by pressing it against the side of the roll, a ferromagnetic material is installed inside the roll, and a side weir composed of refractory and ferromagnetic material is used to provide a space between the roll and the side weir. A direct current magnetic field is applied to the roll and a direct current is applied along the direction in which the thin plate slab comes out of the roll, so that an electromagnetic force acts on the molten metal at the corner between the roll and the side weir, and the side weir A method for preventing leakage of molten metal in twin-roll type thin plate continuous casting, characterized in that leakage of molten metal from the gap between the roll and the roll is prevented. 2. A twin-roll type thin plate continuous casting for producing a thin plate-shaped slab by pouring molten metal into a gap between a pair of rolls rotating in opposite directions and solidifying the molten metal. By holding the molten metal between the rolls by pressing it against the sides of the rolls, a ferromagnetic substance was installed inside the rolls, and a magnetic field was applied to the end of each roll from the outside of the side dam made of refractory. By generating a magnetic field between the roll and the side weir and applying a direct current along the direction in which the thin plate slab comes out of the roll, an electromagnetic force is applied to the molten metal at the corner of the roll and the side weir. To prevent the molten metal from leaking from the gap between the side dam and the roll, thereby preventing the molten metal from leaking in twin-roll type thin plate continuous casting.