JPS60250862A - Preventing method of clogging in tundish nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To prevent surely clogging in a nozzle by installing a coil to the upper part of the nozzle so as to encircle the flow of a molten metal and interrupting the contact between the molten metal and the inside wall of the nozzle by the electromagnetic force of high-frequency current. CONSTITUTION:The coil 7 is provided in the refractory forming the upper part 2a of the tundish nozzle 2 so as to encircle the flow 6a of the molten metal 6. The electric current is induced by the alternating field in the flow 6a of the molten metal when the high-frequency current is passed to the coil 7. The electromagnetic force directed toward the center of the flow 6a is generated by such current and alternating field. the flow 6a of the molten steel is throttled and the section is shrunk, by which the contact between the inside wall 4a of the upper part 2a of the nozzle and the flow 6a is interrupted when the electromagnetic force attains the static pressure of the molten steel 6 or above. The inside wall 4a is thus prevented from being stuck by alumina, etc. and the clogging in the nozzle hole 5 is surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for preventing blockage of a tundish nozzle for continuous casting.

[Prior art and its problems]

In continuous steel casting, a multi-continuous casting method is generally used in which multiple charges of molten steel are cast using one tundish. One of the factors that impede this multi-continuous casting method is nozzle clogging due to alumina in molten steel adhering to the inner wall of the tundish nozzle.

FIG. 4 is a sectional view of the tundish nozzle showing how the nozzle is blocked. In Figure 4, 1 is tandish, 2
3 is a tundish nozzle attached to the bottom of the tundish 1, and 3 is alumina attached to the inner wall 4 of the tundish nozzle 2. The alumina 3 is the upper part 2a of the nozzle 2 where molten steel enters the tundish nozzle 2 from the tundish 1.
(Typically, a large amount of it adheres to the inner wall 4a of D, and the nozzle hole 5 is blocked at this position.

Conventionally, in order to prevent such nozzle clogging, for example, the inner wall of the tundish nozzle was made of porous refractory material and argon gas was blown into the nozzle, but the effect was insufficient and stable. The current situation is that we have not been able to obtain this.

[Purpose of the invention]

In view of the above-mentioned current situation, it is an object of the present invention to provide a method for preventing blockage of a tundish nozzle for continuous casting, which prevents the upper part of the tundish nozzle from being blocked by inclusions in molten metal such as alumina in molten steel. purpose.

[Summary of the invention]

In this invention, a coil that surrounds the flow of the molten metal is installed in a refractory that forms the upper part of the tundish nozzle into which the molten metal flows from the tundish, and a high-frequency current is passed through the coil. An electromagnetic force is generated in the flow toward the center of the flow to cause the molten metal to flow down without contacting the inner wall at the upper part of the tundish nozzle, thus preventing inclusions in the molten metal from adhering to the inner wall. The feature is that it prevents

[Structure of the invention]

The present invention will be explained in detail below.

There are various reasons why alumina in molten steel may adhere to the inner wall of the nozzle, but at least if the molten steel passes through the nozzle without coming into contact with the inner wall, alumina will not adhere.

Therefore, in this invention, by utilizing the electrical conductivity of molten steel, compressive force by a high-frequency electromagnetic field is applied to the molten steel at the upper part of the tundish nozzle where the molten steel flows from the tundish. This is to prevent the molten steel from adhering to the inner wall at the upper part of the tundish nozzle by preventing the molten steel from coming into contact with the inner wall.

FIG. 1 is an explanatory diagram showing one embodiment of the method of the present invention.

In Figure 1, 1 is tundish, 2 is tundish 1
A tundish nozzle 6 is installed at the bottom of the tundish 1, and molten steel is contained in the tundish 1. Inside the refractory forming the upper part 2a of the tundish nozzle 2, there is a tundish nozzle 6 that surrounds the flow 6a of the molten steel 6 flowing from the tundish 1. A coil 7 is installed in the. A high frequency current is passed through this coil 7,
A compressive force is applied to the flow 6a of molten steel.

When a high-frequency current is passed through the coil 7, a stain current is induced in the molten steel flow 6a by the alternating magnetic field of the coil 7, and this current and the alternating magnetic field generate an electromagnetic force directed toward the center of the molten steel flow 6a. However, the molten steel flow 6a is compressed toward the center of the flow. When this electromagnetic force py exceeds the static pressure of the molten steel 6 in the dish 1, the flow 6a of the molten steel is constricted and its cross section contracts, as shown in the figure. Therefore, the flow of molten steel 6a
passes through without contacting the inner wall 4a of the tundish nozzle upper part 2a, thereby preventing alumina in the molten steel 6 from adhering to the inner wall 4a and preventing the nozzle hole 5 from being blocked by the tundish nozzle upper part 2a. It can be prevented.

The frequency and magnitude of the high-frequency current flowing through the coil 7 are determined based on the structure and dimensions of the coil and the static pressure of the molten steel 6 in the kundish 1, so that the electromagnetic force acting on the molten steel flow 6a Decide as appropriate so that it is equal to or higher than the pressure.

Next, examples will be described.

As shown in Fig. 2, a coil 7 is installed in the refractory forming the upper part 2a of the two tundish nozzles 2 of the vertical two-strand bloom continuous casting machine so as to surround the flow 6a of the molten steel 6. , by passing a high frequency current through this coil 7,
Casting was performed by pouring the molten steel 6 into the mold 8 while preventing the alumina in the molten steel 6 from adhering to the inner wall 4a of the tundish nozzle upper part 2a.

The steel type of molten steel 6 is 545C, C: 0.4°5%l Sl
: 0.25%, Mn: 0.75%, P: O
,'020%.

S: 0.020% and 5otAA: 0.035%
Contains. Cast plume 9 is 400X520
It has a circular cross-sectional shape, and its casting speed is 0.5-2n.
It is. Coil 7 has 12 KHz, 700.0OA
・Turn current was applied.

The amount of alumina adhering to the inner wall 4a of the tundish nozzle upper part 2a when seven continuous charges of molten steel were cast was investigated, and the results were as shown in FIG.

As is clear from FIG. 3, the amount of alumina deposited when casting was performed while preventing clogging by the method of the present invention (indicated as the present invention in the figure), and when casting was performed without preventing clogging (in the figure, This is a drastic decrease to about one-tenth of that of the conventional method (shown as conventional), and it can be seen that the method of the present invention can reliably prevent the upper part of the tundish nozzle from being clogged due to alumina adhesion.

〔Effect of the invention〕

As explained above, according to the method of the present invention, clogging of the Kundishu nozzle due to adhesion of alumina in molten steel can be reliably prevented. It goes without saying that the method of the present invention can also be applied to continuous casting of other metals besides steel.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the method of the present invention, Fig. 2 is an explanatory diagram showing continuous casting of plumes while preventing blockage by the method of the present invention, and Fig. 3 is an explanatory diagram showing the method of the present invention. FIG. 4 is a graph showing the amount of alumina deposited with and without blockage prevention. FIG. 4 is a cross-sectional view showing the state of nozzle blockage in a conventional tundish nozzle. In the drawings, 1...Tundish, 2...Tundish nozzle, 2
a... Upper part of tundish nozzle, 3... Alumina, 4 + 4 a... In, 5...
Nozzle hole, 6... Molten steel, 6a... Molten steel flow, 7... Coil, 8... Mold, 9... Plume Applicant Natsuo Shioya, agent of Nippon Kokan Co., Ltd. (and 2 others) ) Figure 1

Claims (1)

[Claims] A coil surrounding the flow of the molten metal is installed in the refractory that forms the upper part of the tundish nozzle into which the molten metal flows from the tundish, and by passing a high frequency current through the coil, the center of the flow is set in the flow of the molten metal. The molten metal is caused to flow down without coming into contact with the inner wall at the upper part of the tundish nozzle by generating an electromagnetic force directed toward the tundish nozzle, thereby preventing inclusions in the molten metal from adhering to the inner wall. A method for preventing blockage of a tundish nozzle for continuous casting.