JPH0324274Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for supplying molten metal from a tundish to a mold in continuous casting, and more specifically to a pouring method using an electromagnetic pump.

(Prior technology) Methods for controlling the amount of molten metal injected into the mold from a continuous casting tandy include selecting the nozzle diameter according to the flow rate, or using a large diameter nozzle and controlling the injection amount with a stopper or slide valve. There is a way to do it. Furthermore, in recent years, flow control methods using linear motor type coils (for example, FR Block, Technische Forschung
Stahl (1980) and Steel Engineering Research (Recherchetechnique acier) (1980))
is also introduced.

These methods have problems as described below.

First, the method of selecting the nozzle diameter according to the flow rate is usually used in continuous billet casting, but since this method uses a nozzle with a small diameter of about 10 to 14φ, it is easy to cause nozzle clogging.
It is not suitable for casting steel types that are prone to Al ₂ O ₃ adhesion, such as Al-killed steel.

The next method is to use a stopper or a slide valve, but the stopper makes it difficult to control the flow rate, and the slide valve sucks air from the sliding surface of the refractory material, resulting in an increase in the amount of inclusions in the steel.

Furthermore, in the method using a linear motor, in order for the electromagnetic force of the linear motor to effectively act on the molten metal, the diameter of the refractory that makes up the electromagnetic gutter must be made small, flat, and long. The drawback is that the nozzle can easily become clogged inside.

On the other hand, the present inventors devised an electromagnetic valve using a rotating magnetic field type coil as shown in Fig. 3.
−43818). This electromagnetic valve is installed in a disc-shaped refractory container 2 under the molten steel discharge port of the tundish 1.
is connected. The shape of this refractory container 2 is
As shown in the cross-sectional view of the figure, it is a cylinder with a low height, with an inlet 2a for receiving the molten metal 3 at the end of the upper surface, and an immersion nozzle for injecting the molten metal 3 into the mold 4 at the center of the lower surface. Attach 5. Electromagnetic coils 6, 6, . . . are installed around the refractory container 2, and connected to an AC power source (not shown) for driving with a rotating magnetic field. A conventional electromagnetic valve is composed of a refractory container 2 and the electromagnetic coils 6, 6, . . . connected in a rotating magnetic field type.

During continuous casting, the rotating magnetic field type electromagnetic coil 6,
By applying alternating current to 6, . . . , the molten steel inside the refractory container 2 is made to rotate and flow. As the rotational flow rate increases, the pressure difference between the periphery and the center increases, and upward pressure is generated in the molten metal 3 in the upper tundish from the inlet 2a provided at the periphery of the refractory container 2. This upward dynamic pressure reduces the static pressure of the molten metal 3 in the tundish, and the flow rate is controlled by adjusting the rotational flow rate. This electromagnetic pump is the same as a conventional electromagnetic transfer gutter in that it transfers molten steel using electromagnetic force, but it also uses a new adjustment mechanism that adjusts the injection amount using dynamic pressure generated by rotational flow. It is something.

According to this method, a thick nozzle that can reduce the flow rate can be used, so the problem of nozzle clogging caused by using a small diameter nozzle as in the case of continuous billet casting is improved. Furthermore, the fact that rotational flow is imparted to the injected flow flowing out from the center of the disk also helps to prevent nozzle clogging. In addition, the flow rate can be easily controlled by adjusting the current,
Since there are no refractory sliding parts, there is no problem with air intake. Furthermore, unlike the method using a linear motor, there is no need to use a long refractory material with a small inner diameter, so the problem of nozzle clogging is less likely to occur.

(Problems to be solved by the invention) Although the method using a rotating magnetic field coil has many advantages over the conventional method, there are cases where the disc-shaped refractory container is not completely filled with molten metal. This is because there is only one nozzle hole 2a in the part that communicates with the tundish, so the air inside the disc-shaped refractory container is difficult to be pushed out.
In such a case, since there is insufficient molten metal in the disc-shaped refractory container, sufficient rotational force is not applied, making it difficult to control the flow rate. Furthermore, if an accident such as a slab breakout under the mold occurs, it is necessary to stop injection immediately, and in preparation for such an emergency, it is also necessary to use a method to completely stop the flow of molten steel. Become. Completely stopping the injection flow requires a considerable rotational flow rate, which requires a considerably large electromagnetic coil and power supply capacity.

An object of the present invention is to provide an electromagnetic valve that can easily control the flow rate of molten metal poured from a tundish into a mold using electromagnetic force in continuous casting, and that does not cause nozzle clogging.

(Means for Solving the Problems) In order to solve the above problems, the present inventors devised a system in which a large refractory stopper is placed at the center of the rotating molten metal flow, as shown in FIG.

That is, the valve for a continuous casting tundish according to the present invention is a cylindrical molten metal container that has an opening for taking in molten metal from the tundish over almost the entire top surface and an outlet for discharging the molten metal to the mold in the center of the bottom surface. , which is provided above the opening so as to be able to rise and fall freely, and has a tip having a shape that closes the opening when it comes into contact with the opening, and during continuous casting, forms a gap around the outer periphery of the opening, and as required. In such a case, the method comprises an injection control means for closing the opening, and an electromagnetic coil provided on the side surface of the molten metal container and generating a rotating magnetic field in a direction perpendicular to the side surface.

(Action and effect of the invention) The passage between the cylindrical molten metal container is widened, and the molten metal in the tundish and the molten metal in the cylindrical molten metal container are communicated over the entire outer circumference of the tundish and molten metal container, and the molten metal in the cylindrical molten metal container is expanded. air bubbles are easily extruded by the molten metal. As a result, flow rate control becomes easy.
Furthermore, in the event of a breakout accident, the injection flow can be easily stopped by lowering the stopper.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a conceptual diagram of an electromagnetic pump for continuous casting tundish according to the present invention. A cylindrical refractory container 13 is provided at the bottom of a tundish 12 containing molten metal 11. A nozzle 14 for discharging molten metal is provided at the center of the bottom of the refractory container 13. The diameter of the opening 15 leading from the tundish 12 to the refractory container 13 is made to be approximately the same as the inner diameter of the refractory container 13. Further, a stopper 16 is attached above the opening 15 so as to be able to rise and fall freely. The tip of the stopper 16 has a downward truncated conical shape. Lower end surface 1 of stopper 16
6a is positioned lower than the opening 15 so that a gap between the outer periphery of the opening 15 and the stopper 16 is formed only at the outer periphery of the refractory container. As a result, the molten metal 11
flows into the refractory container 13 from the outer periphery. If necessary, the stopper 16 can be lowered to close the opening 15 and stop the flow of molten metal. Rotating magnetic field type coils 17, 17, . . . are arranged around the refractory container.

The flow rate control from the nozzle 14 to a mold (not shown) is performed on the same principle as a conventional electromagnetic pump (FIG. 3).

FIG. 2a shows the results of a comparison of flow rate control between the conventional electromagnetic pump (FIG. 3) and the electromagnetic pump according to this embodiment. The electromagnetic valve used in the test (second
(see Figure b), the height of the cylindrical refractory container 13 is 320 mm, the inner diameter is 160 mm, and the nozzle inner diameter is 20 mm.
The width of the gap between the stopper 16 and the cylindrical refractory container 13 is the same as that of the inlet 2 between the tundish 3 and the disc-shaped refractory container 2 in the conventional method (see Fig. 2c).
I made it the same size as the hole diameter (55φ) in a. 200Kg
Molten steel with 0.6% C is used, and the height of the molten steel head in the tundish is 75 mm at maximum.

In the conventional example (see Figure 2c), the size of the refractory container is the same, but the inlet between the tundish and the refractory container is provided on the outer periphery of the upper surface of the refractory container. are different.

Although both electromagnetic pumps operate on the same principle, as is clear from FIG. 2a, there was a large difference in flow control characteristics. In the conventional example, due to residual air bubbles, the flow rate decreases as the coil current increases, but the variation is large. In contrast, in this embodiment, there is almost no variation, and stable flow rate control is possible. Further, by lowering the stopper 16 and closing the opening 15, the injection flow could be easily blocked.

Furthermore, as shown in Utility Application No. 59-43818, when the rotation speed is decreased and the flow rate is increased,
By applying reverse control for about 1 second and then adjusting the current in the electromagnetic coil to the lower strength of forward rotation, the influence of the inertia of the molten steel flow was quickly canceled out, and the flow rate could be quickly controlled.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram for explaining the present invention. FIG. 2a is a graph of the flow rate control characteristics of the conventional example and the embodiment of the present invention. FIGS. 2b and 2c are diagrams schematically showing the present embodiment and a conventional electromagnetic pump, respectively. FIG. 3 is a conceptual diagram of a conventional electromagnetic pump. 12... Tandishi, 13... Refractory container, 14... Nozzle, 15... Opening, 16... Stopper.

Claims (1)

[Scope of Claim for Utility Model Registration] A cylindrical molten metal container having an opening for taking in molten metal from a tundish cylinder on almost the entire surface of the upper surface and an outlet for discharging the molten metal to the mold in the center of the lower surface; It is provided with a tip that can be raised and lowered upwards and has a shape that closes the opening when it reaches the opening, and during continuous casting, a gap is formed around the outer periphery of the opening, and if necessary, the opening is closed. An electromagnetic valve for a continuous casting tundish, comprising an injection control means for closing an opening of the molten metal container, and an electromagnetic coil provided on the side surface of the molten metal container and generating a rotating magnetic field in a direction perpendicular to the side surface.