JPH0592243A - Method for starting casting in continuous casting - Google Patents

Abstract

PURPOSE:To start a casting without generating a nozzle clogging caused by solidification of a molten steel in the upper nozzle of a tundish. CONSTITUTION:By making the sliding plate 6 of a sliding nozzle 9 a closing condition in advance, after the formed thermite-based heating material 1 is packed into the nozzle hole over the interval from an upper nozzle 2 to the sliding plate 6, the pouring of the molten steel into the tundish 8 is started and while heating and warm-keeping the molten steel with the thermite-based heating material 1, the molten steel is pooled in the tundish 8. By melting the steel with the rise of temp. of the heating material 1, the nozzle hole is naturally opened and the casting is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when starting the injection of molten steel into a tundish equipped with a sliding nozzle for opening and closing a sliding plate in contact with the lower surface of a fixed plate provided in the lower part of a tundish upper nozzle, The present invention relates to a casting start method in continuous casting that prevents molten steel from solidifying in a nozzle hole.

[0002]

2. Description of the Related Art In continuous casting of molten steel, a sliding nozzle is used for flowing out and stopping the molten steel from a tundish. Generally, the sliding plate of the sliding nozzle is closed to keep a certain amount of molten steel in the tundish at the beginning of casting, so when the molten steel was poured into the tundish, it accumulated in the upper nozzle of the tundish. The molten steel solidifies due to the cooling action of the peripheral wall of the nozzle hole, causing nozzle clogging.

At this time, in order to prevent the solidification of the molten steel in the tundish nozzle hole, a gas is blown into the nozzle hole to stir the molten steel, or as disclosed in JP-A-55-86677. A method is known in which a granular refractory material is filled inside. As a method of keeping the sliding plate open and holding the molten steel, a method of using a wooden plug that closes the nozzle hole is known.

[0004]

However, the method of blowing the gas into the nozzle hole with the sliding plate in the closed state requires additional equipment for blowing the gas, resulting in high cost. In addition, in a method in which the sliding plate is kept closed and filled with granular refractory, the molten steel solidifies on the surface of the filled refractory and the nozzle is clogged, and the filled refractory flows into the mold and is cast. There is a one-sided defect. Furthermore, with the method of holding the molten steel with a wooden plug while keeping the sliding plate open, it was difficult to start casting at a stable timing due to the quality variation of the wooden plug.

The present invention solves the above problems of the prior art,
When the filler to fill the nozzle hole with the sliding plate of the sliding nozzle in the open state injects the molten steel into the tundish, an exothermic reaction occurs, which prevents solidification of the molten steel on the surface of the filler in continuous casting. It is intended to provide a casting start method.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a tundish equipped with a sliding nozzle which is opened and closed by a sliding plate in contact with the lower surface of a fixed plate provided at the lower part of the tundish upper nozzle. When starting the molten steel injection, the sliding plate of the sliding nozzle is opened in advance, and is molded in the nozzle hole extending from the tundish upper nozzle to the sliding plate according to the hole circumferential shape of the tundish upper nozzle. After injecting molten steel into the tundish after filling with the thermite heating material, the temperature of the molten steel is kept warm by the thermite heating material filled in the nozzle hole, and the nozzle hole is melted by raising the temperature. Is a method for starting casting in continuous casting, which is characterized in that

[0007]

[Operation] In the case of the present invention, since a thermite heat generating material is used as the filler in the nozzle of the tundish, the exothermic reaction occurs at the contact surface between the filler surface and the molten steel to prevent the molten steel from solidifying. Since the sliding plate of the sliding nozzle is already open, it melts due to the temperature rise due to the exothermic reaction of the thermite heating material, the nozzle holes open naturally, and the molten steel in the tundish starts casting without causing nozzle clogging. To be done.

As the oxidizable substance in the heat insulating material,
One or more elements selected from Al, Ca, Si, Ti, and Mg, alloys, metal compounds, or mixtures thereof are used. The oxygen supply material to the easily reducing substance is selected from oxides of iron or manganese, nitrates of alkali or alkaline earth elements, and chlorates.
Species or two or more single or complex compounds or mixtures can be used.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. A thermite heat generating material 1 was produced from the heat generating composition shown in Table 1 as shown in FIG. The shape and dimensions of the exothermic composition portion here are, as shown in FIG. 2, a shape close to a conical shape having an upper end diameter of 80 mm and a lower end diameter of 60 mm.

[0010]

[Table 1]

FIG. 1 shows a state in which a sliding nozzle 9 is attached to an upper nozzle 2 of a tundish 8, and the upper nozzle 2 is normally fitted to a lower wide taper portion 4a of a tuyere brick 4 embedded in a floor brick 3. It is set up. A fixed plate 5 is provided in contact with the lower surface of the upper nozzle 2, and a sliding plate 6 that is in contact with the fixed plate 5 and slides and has an opening 6a is provided. A lower nozzle 7 is further attached to the sliding plate 6, and these constitute a sliding nozzle 9.

According to the present invention, as shown in FIG. 1, a tundish for continuous casting having a capacity of 20 ton equipped with a sliding nozzle 9 is preheated, and then a sliding plate 6 of the sliding nozzle 9 is preliminarily opened so that the upper nozzle 2 is removed. The thermite-based heat generating material 1 molded according to the hole peripheral wall shape of the upper nozzle 2 was filled in the nozzle hole extending over the sliding plate 6. Approximately 5 minutes after the thermite heating material 1 was filled in the nozzle hole, injection of molten steel from the ladle into the tundish 8 was started, and 1 minute after that, about 10 tons of molten steel was retained in the tundish 8. The nozzle hole was naturally opened by melting the heat generating material 1, and the continuous casting operation was started. In the operation by this method, when the number of times of use shown in Table 2 was 20, the natural porosity was 100% and the refractory condition in the nozzle was good.

[0013]

[Table 2]

On the other hand, in the conventional method in which the gas is blown into the upper nozzle, the aperture ratio is 90 due to the nozzle clogging.

[0015]

As described above, according to the present invention, the thermite-type invention material is filled in the nozzle hole of the tundish with the sliding plate of the sliding nozzle kept open, so that the heat-generating and heat-retaining action of the molten steel causes The nozzle blockage due to solidification can be prevented and a stable natural opening can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a tundish nozzle and a sliding nozzle according to the present invention.

FIG. 2 is an explanatory view showing the shape of a thermite heat generating material according to the present invention.

[Explanation of symbols]

 1 Thermite heat generating material 2 Upper nozzle 3 Floor brick 4 Tuyere brick 5 Fixed plate 6 Sliding plate 7 Lower nozzle 8 Tundish 9 Sliding nozzle

Claims (1)

[Claims] 1. Sliding of the sliding nozzle in advance when starting the injection of molten steel into a tundish equipped with a sliding nozzle that opens and closes by a sliding plate in contact with the lower surface of a fixed plate provided at the lower part of the upper nozzle of the tundish. With the plate in the open state, in the nozzle hole extending from the tundish upper nozzle to the sliding plate, after filling the thermite heat generating material molded in accordance with the hole peripheral wall shape of the tundish upper nozzle, to the tundish Starting the injection of molten steel, while keeping the molten steel heated by the thermite heating material filled in the nozzle holes, the nozzle holes are naturally opened by the melting of the heating materials due to temperature rise Method.