JPH0638603Y2 - Molten metal flow pipe for electric heating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a molten metal having a mechanism for directly heating the distribution pipe by electrically heating the distribution pipe in order to prevent the metal from adhering to the inside of the distribution pipe. Regarding distribution pipes.

[Conventional technology]

For example, when pouring molten metal into a mold from a tundish in a continuous casting machine, in order to prevent oxidation of the molten metal due to contact with the atmosphere, the molten metal flows in a state where the space between the tundish and the mold is blocked from the outside air. Immersion nozzles and long nozzles are used. This nozzle has thermal shock resistance such as alumina-carbon, corrosion resistance, melting resistance, etc.
Materials made of refractory having excellent wear resistance have been used.

However, when the molten metal is injected using such an injection nozzle, the temperature of the molten metal may be lowered, especially at the initial stage of casting or the final stage of casting, and the molten metal solidifies due to this temperature decrease and the inner wall of the nozzle is solidified. It becomes easy to adhere. Further, such a tendency also occurs when casting a low temperature cast steel grade. If metal is attached to the inner wall of the nozzle, the flow state of the molten metal becomes unstable, and eventually the nozzle may be clogged and casting may not be possible. In order to prevent the adhesion of the metal, a heat insulating material is wrapped around the outer surface of the nozzle to prevent heat radiation, but this is not sufficient.

Therefore, for example, JP-A-55-64857 discloses that the refractory forming the nozzle is directly energized and the temperature of the nozzle is maintained by electric heating utilizing electric resistance.
FIG. 3 is a diagram for explaining the outline of this electric heating method. The nozzle 1 to be heated is provided with a pair of electrodes 2 for energization heating on its peripheral surface. Then, the nozzle 1 is heated by energizing the nozzle 1 from the conductor 3 such as a bus bar through the electric heating electrode 2.

In this direct current heating, it is important how the contact state between the electrode and the nozzle contact portion can be stabilized, and the nozzle configuration can withstand the long-time heating during continuous casting.

[Problems to be solved by the invention]

For example, in the conventional method, in order to make contact between the nozzle 1 and the electrode 2 for electric heating, the contact surface of the electrode 2 for electric heating is formed into a concave shape in accordance with the cylindrical nozzle 1, and a space between the two is formed. A graphite sheet 4 which is a contact resistance reducing material is interposed between the nozzle 1 and the electrode 2 for energization heating at a pressure P by an electrode pressing mechanism.
Is pressed against the peripheral surface of. With this shape, in order to obtain a good contact state, it is necessary to improve the accuracy of curved surface processing of the nozzle 1 and the electric heating electrode 2. However, even if the curved surface is processed with high accuracy, the pressure P may not work evenly on the contact surface, and the energization heating electrode 2 may contact the peripheral surface of the nozzle 1 unevenly. Moreover, since a current flows in the opposite direction to the molding direction of the graphite sheet 4 inserted in the contact portion between the nozzle 1 and the electric heating electrode 2, the graphite sheet 4 exhibits a high resistance value. Therefore, this graphite sheet 4
The part heats up and becomes hot.

As a result, the oxidation of the contact part progressed remarkably, and FIG.
As shown in FIG. 3, the contact portion 5 is oxidized and worn, and the main body of the nozzle 1 is damaged. Since the electrode 2 for energization heating is pressed against the nozzle 1 by the pressure P, the nozzle 1 or the electrode 2 for energization heating easily buckles from the contact portion 5 that has been oxidized and consumed. From the above, in the conventional electric heating type nozzle 1,
For example, it has been impossible to electrically heat for a long time such as repeatedly injecting molten steel into a tundish from a ladle.

Such a problem is not limited to the immersion nozzle and the long nozzle of the continuous casting device, and is common to other pipes for flowing molten metal.

In view of this, the present invention solves the problem caused by poor contact and improves the durability of the flow tube itself by making contact with the current heating electrode at the flat portion of the terminal portion protruding from the peripheral surface of the flow tube. The purpose is to improve.

[Means and Actions for Solving Problems]

In order to achieve the object, the molten metal flow pipe of the present invention has a terminal portion integrally formed with the same conductive refractory as the flow pipe body on the molten metal flow pipe body, projecting from its peripheral wall, The surface of the terminal portion in contact with the electric heating electrode is flat.

FIG. 1 specifically shows this molten metal flow pipe. That is, the nozzle 1 as a molten metal flow pipe made of a conductive refractory material such as alumina-carbon is formed integrally with the terminal portion 6 protruding from the peripheral wall of the main body. The contact surface of the terminal portion 6 that is in contact with the electric heating electrode 2 has a flat shape. That is, the terminal portion 6
And the electric heating electrode 2 contact each other through a flat contact surface. This facilitates the processing of the contact surface between the nozzle 1 and the electrode 2 for electric heating, and improves the processing accuracy.

Further, since the terminal portion 6 of the nozzle 1 is located away from the molten metal flowing in the nozzle 1, the influence of the retained heat of the molten metal is reduced. Further, since the terminal portion 6 is projected, the contact surface with the electric heating electrode 2 can be brought closer to the air-cooled conductor 3, and the temperature of the contact portion can be lowered. As a result, the oxidation rate of the electric heating electrode 2 can be reduced. Further, even if it should be oxidized, as shown in FIG. 2, the oxidized portion stays only at the contact portion 5 between the electrode 2 for energization heating and the terminal portion 6 of the nozzle 1 to prevent the oxidation of the main body of the nozzle 1. You can
In this way, it becomes possible to heat the nozzle 1 under stable conditions for a long time in order to prevent metal adhesion.

〔Example〕

Alumina-carbon conductive refractory with a composition of 75% by weight alumina and 25% by weight carbon, with an inner diameter of 65 mm and an outer diameter of 130 m.
A cylindrical nozzle 1 of m was formed. Further, a terminal portion 6 of 60 × 70 × 20 mm was formed integrally with the main body of the nozzle 1 on the peripheral wall of the nozzle 1. The current-carrying portion of the terminal portion 6 was finished to be a flat surface having a size of 60 × 70 mm. 60 × 70 × 30 mm to the terminal part 6 of this nozzle 1 through the graphite sheet 4 of 0.4 mm thickness
The electrode 2 for electric heating was pressed with a pressing force P = 4 kg / cm ² . The electric heating electrode 2 is in contact with the conductor 3 by a bolt and nut, and the electric power is supplied from the power supply 7 via the conductor 3.

With such a device configuration, the capacity of a ladle with a capacity of 240 tons is 60
The immersion nozzle used when pouring molten steel into a ton tundish was electrically heated. When the immersion nozzle was heated with an energizing current of 3500 A, the outer surface temperature of the immersion nozzle reached 1350 ° C after about 30 minutes, and 10 pots could be continuously used. At this time, the contact portion between the electric heating electrode 2 and the terminal portion 6 is 800
Upon heating to ℃, the amount of oxidative wear of this contact part was about 10 mm. That is, the main body of the nozzle 1 having an outer diameter of 130 mm was not oxidized, and the terminal portion 6 was consumed only by oxidation.

On the other hand, in the case of the nozzle 1 shown in FIG. 3, the contact surface between the nozzle 1 and the electric heating electrode 2 is 1100.
The contact portion 5 heated to 0 ° C. and consumed by oxidation reached a depth of 15 mm with respect to the nozzle 1 main body having an outer diameter of 130 mm. That is, the damage of the nozzle 1 in this case was remarkable, and the service life of 10 pots or more was limited.

In the above example, the electric heating of the immersion nozzle used in the continuous casting apparatus has been described. However, it is needless to say that the present invention is not limited to this, and is similarly applied to a flow pipe for flowing molten metal such as a long nozzle between a ladle and a tundish. .

[Effect of device]

As described above, according to the present invention, it is possible to easily improve the processing accuracy by forming the surface of the terminal portion projecting on the peripheral wall of the molten metal flow pipe in contact with the electric heating electrode to be flat. In addition, it is possible to bring the electrode for electric heating and the terminal portion into uniform pressure contact. As a result, it is possible to prevent local abnormal heating from occurring on the contact surface, and to suppress damage to the nozzle and the electric heating electrode. In this way, according to the present invention, it becomes possible to stably heat the metal flow pipe for a long time in order to prevent adhesion of metal, and for example, injecting molten metal in continuous casting is performed under stable conditions. It becomes possible.

[Brief description of drawings]

FIG. 1 shows a nozzle equipped with an electric heating mechanism in an embodiment of the present invention, FIG. 2 shows a state in which the nozzle is oxidized, and FIG. 3 shows a nozzle equipped with a conventional electric heating mechanism.

Claims (1)

[Scope of utility model registration request] 1. A molten metal flow pipe main body having a terminal portion which is integrally formed of the same conductive refractory as the flow pipe main body and which protrudes from the peripheral wall of the flow pipe main body. A molten metal flow pipe for electric heating, which is made flat.