JPH05138303A - 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 and the side surfaces of the rolls in the twin roll strip continuous casting. CONSTITUTION:By arranging magnets 8a, 8b and ferromagnetic, body 9 at the outside of the side weir 4 or four magnets per one side weir at the outside of the side weir 4, the magnetic field is impressed in the molten metal 6. By impressing DC current in the molten metal 6 along the drawing-out direction of the cast strip 7 from gap between the rolls 1a, 1b, the electromagnetic force is acted to the molten metal 6 between the rolls 1a, 1b to prevent the leakage of the molten metal 6 from the gap between the side weir 4 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]

As a technical problem of twin roll type thin plate continuous casting, it is possible to completely prevent the molten metal from entering the gap between the side dam and the side surface of the roll and the resulting leakage of the molten metal, so that the end portion is prevented. In some cases, a thin plate slab having a good shape may be manufactured, and the life of the side dam may be extended to enable long-time casting.

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 a method in which a magnetic field is generated in the roll gap without using side dams and the molten metal between the rolls is held by the action of the magnetic field, 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.

If the shape of the end of the cast piece becomes defective, it is necessary to cut the end portion of the cast piece to make the width uniform in the process of commercialization.
Yield decrease and work process increase are problems.

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]

DISCLOSURE OF THE INVENTION The present invention is 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 and solidifying the molten metal,
When the side weir is pressed against the side of the roll to hold the molten metal between the rolls for casting, a magnet and a ferromagnetic material are installed outside the side weir made of refractory, or four side weirs are used. A magnetic field is applied to the molten metal at the corners of the roll and the side dam by installing a magnet, and a direct current is applied to the molten metal in 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 side dam to prevent leakage of the molten metal from the gap between the side dam and the roll. is there.

[0009]

1 is a drawing showing a method of preventing leakage of molten metal when a ferromagnetic material and a magnet are installed outside the side dam. That is, the molten metal 6 is poured into the space between the pair of rotating rolls 1a and 1b and the side dam 4 made of refractory through a pouring nozzle, and the molten metal is solidified by heat removal to the roll side. Side weir 4 when producing a slab
A ferromagnetic material 9 and magnets 8a and 8b are installed outside the magnetic field, a magnetic field is applied to the molten metal at the corners of the roll and the side dam, and the electrodes 10a and 10b immersed in the molten metal face the lower electrode 13. To apply a direct current. The magnet 8
The a and 8b may be permanent magnets or magnetic poles N and S of one electromagnet. Regarding the position of the electrode, it is preferable that the electrode is immersed 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 is a sectional view taken along the line AA 'in FIG. When the ferromagnetic body 9 and the magnets 8a and 8b are installed outside the side dam 4 made of refractory, and a magnetic field is applied from the magnets 8b to 8a through the ferromagnetic body 9, as schematically shown by magnetic force lines 17, A magnetic field B is generated in the molten metal 6 at the corners of the roll 1b and the side dam 4, and at the corners of the roll 1a and the side dam 4. When a current J is applied to this magnetic field, the action of the magnetic field and the current causes an electromagnetic force F toward the central portion in the roll axis direction.
Is generated inside the molten metal and the molten metal can be prevented from entering the gaps 16a and 16b between the roll side surface and the side dam. If the molten metal can be prevented from entering the gaps 16a and 16b, it is possible to prevent the formation of a casting burr at the end of the cast slab due to the penetration and the leakage of the molten metal due to the casting burr scraping the side weir, and the casting with a good end shape. The pieces can be manufactured continuously.

As an example of another method for applying a magnetic field to the molten metal from the outside of the side weir, FIG. 3 shows a case where four electromagnets having irregular cross sections are installed outside the side weir, and FIG. The sectional view of the position of BB 'is shown. Electromagnet 18a,
Since the positions of the magnetic poles N and S can be changed by changing the directions of the currents flowing through 18b, 19a, and 19b, the electromagnet 1 is arranged so that the magnetic poles N and S are arranged as shown in FIG.
When 8a, 18b, 19a and 19b are installed, the magnetic field lines 1
As schematically shown by 7, a magnetic field B is generated in the molten metal 6 at the corners of the roll 1b and the side weir 4 and at the corners of the roll 1a and the side weir 4. Here, when a current J is applied to the molten metal 6 by a method similar to the method shown in FIG. 1, an electromagnetic force F toward the central portion in the roll axis direction as shown in FIG. It is possible to prevent the molten metal from being generated inside and leaking into the gap between the side surface of the roll and the side weir and from leaking.

If the strength of the magnetic field generated between the roll and the side weir is sufficiently high, 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. However, it is advantageous to lightly press the side weir against the side surface of the roll for casting in order to completely prevent leakage of the molten metal.
In this case, the gap between the roll and the side weir depends on the parallelism and the roughness of the roll side surface and the side weir surface, but there is usually a gap of about 0.1 to 0.3 mm regardless of the effort. If not applied, the molten metal enters the gap as the depth of the molten metal becomes deeper, but by applying the present invention, the molten metal does not enter the gap between the roll and the side dam,
Can completely prevent leakage.

[0013]

【Example】

Example 1 An austenitic stainless steel casting experiment was conducted using a twin roll casting machine having a roll diameter of 300 mm and a body length of 100 mm. Nonmagnetic stainless steel is used for the paramagnetic bodies 2a and 2b and the roll shafts 3a and 3b of the rolls shown in FIGS. 1 and 2, and two permanent magnets and one ferromagnetic iron are used to apply a magnetic field. It was installed outside the side dam 4.
When the distance between the ferromagnetic body 9 and the magnets 8a and 8b was about 5 mm, the magnetic field strength between the ferromagnetic body 9 and the magnets 8a and 8b was about 1.5 tesla. A fibrous alumina refractory was used as the side weir 4, and was lightly pressed against the side surfaces of the rolls 1a and 1b. On the other hand, as shown in FIG. 1, the electrodes 10a and 10b made of ZrB ₂ are immersed in the molten metal 6 near the weir 4,
A direct current of 0 to 500 A was applied. It should be noted that the rolls 1a and 1b are arranged so that the current does not leak through the rolls 1a and 1b.
Insulation was applied at the bearing part of b. As operating conditions, the roll rotation speed is 10 to 100 rpm, the molten metal pouring flow rate is variously changed in the range of 0.3 to 1.5 kg / sec, and the height of the molten metal between the rolls becomes constant at about 100 mm. The pouring flow rate was adjusted as follows.

As a result of this experiment, when the intensity of the current applied to the molten metal 6 is small, a casting burr is formed at the end of the cast piece, and the molten metal 6 is removed from the gap between the rolls 1a and 1b and the side dam 4. Although it leaked, when the strength of the current was increased to a certain extent or more, the molten metal 6 did not leak from the gap between the rolls 1a, 1b and the side dam 4 due to the electromagnetic force generated in the molten metal 6 by the action of the magnetic field and the current. , Thickness is about 0.8-3
In mm, a thin plate-shaped slab having a good end shape and a uniform width was obtained. Under this experimental condition, if the applied DC current is about 250 A or more, the side weir 4 and the roll 1a,
It is possible to completely prevent leakage of the molten metal 6 from the gap 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.

Example 2 As shown in FIGS. 3 and 4, a magnetic field was applied to the molten metal 6 using electromagnets 18a, 18b, 19a and 19b installed outside the side dam 4, and a method similar to that shown in FIG. Then, a direct current was applied in the direction in which the slab came out of the roll, and a casting experiment was conducted. The experimental conditions other than the method of generating the magnetic field were the same as in Example 1.
It is as explained in. In this experiment, electromagnets 18a, 18b, 19a in which a copper wire is wound around an iron core of a ferromagnetic material many times,
A magnetic field is generated by applying a direct current to 19b,
As shown in FIG. 4, electromagnets 18a, 18b, 19a, 1
A casting experiment was conducted by applying a magnetic field generated from 9b toward the ends of the rolls 1a and 1b to generate a magnetic field between the rolls 1a and 1b and the side dam 4. The strength of the magnetic field is about 0.1
It was 0.5 Tesla. Moreover, the direct current value applied to the molten metal 6 was set to 300 to 400A. The result of this experiment
If an electromagnetic force is not applied to the molten metal, a casting burr is formed at the end of the slab and the molten metal leaks from the gap between the rolls 1a, 1b and the side dam 4, but a magnetic field is applied from the outside of the side dam 4. Moreover, by applying a direct current to the molten metal along the direction in which the slab comes out from between the rolls 1a and 1b, the thickness is about 1 to 3 mm, there is no casting burr, and the end shape is good. A thin plate slab could be manufactured.

[0016]

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 diagram showing a method for preventing leakage of molten metal when a ferromagnetic material and a magnet are installed outside a side dam.

FIG. 2 is a sectional view taken along the line AA ′ in FIG.

FIG. 3 is a diagram showing a method for preventing leakage of molten metal when four electromagnets are installed outside a side dam.

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

[Explanation of symbols]

 1a, 1b Roll 2a, 2b Paramagnetic material 3a, 3b Roll shaft 4 Side weir 5 Pouring flow 6 Molten metal 7 Thin plate cast 8a, 8b Magnet 9 Ferromagnetic material 10a, 10b Electrode 11 DC power supply 12 Current flow direction 13 Lower electrode 14 Moving direction of cast piece 15 Rotating direction of roll 16a, 16b Gap 17 Magnetic field lines 18a, 18b Electromagnet 19a, 19b Electromagnet

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

Claims (1)

[Claims] 1. In 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 and solidifying the molten metal, a side dam is pressed against a side surface of the rolls to form a space between the rolls. When casting while holding the molten metal of
Applying a magnetic field to the molten metal at the corners of the roll and the side weir by installing magnets and ferromagnets outside the refractory side weir, or by installing four magnets per side weir, and By applying a direct current to the molten metal in the direction in which the thin plate slab goes out of the roll, an electromagnetic force is applied to the molten metal at the corner between the roll and the side dam, and the gap between the side dam and the roll A method for preventing leakage of molten metal in twin-roll type thin plate continuous casting, characterized in that the leakage of molten metal is prevented.