JPH0780611A - Method for opening hole in initial stage in molten steel casting - Google Patents

Abstract

PURPOSE:To further ensure the casting start in the initial stage by preventing the solidification of poured molten steel at the time of pouring the molten steel in the initial stage by using an SN plate. CONSTITUTION:In the nozzle hole opening method in the initial stage for casting the molten steel by slidingly shifting a sliding plate 42 of a sliding nozzle device 4 set at the lower position of an upper nozzle 3 set to the bottom opening hole of a molten steel vessel 2, both of molten steel stirring with bubbling by gas-blowing into the molten steel in the nozzle and intermittent sliding movement at the closed position of the sliding plate are adapted. The low temp. part of the molten steel in the nozzle hole and just above the sliding plate during progressing the solidification and the high temp. part at the central part of the nozzle hole can sufficiently be stirred and the molten steel temp. at the time of starting the casting is uniformized and the molten steel can be poured at a constant flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of initial opening of nozzle holes for starting casting in a continuous casting method using a sliding nozzle (SN) plate device.

[0002]

2. Description of the Related Art In extracting molten steel using a sliding nozzle plate device, as a method for preventing solidification of molten steel, a method of discharging a refractory filling material filled in a nozzle hole, a method of gas bubbling from a nozzle refractory material, Alternatively, there is a method of vibrating molten steel as described in JP-A-57-209770.

However, in the method of releasing the refractory filling, there is a problem that the filling is mixed with the extracted molten steel and the quality is deteriorated, and the gas bubbling itself is in order to prevent the molten steel from solidifying. It is not sufficient to prevent solidification of the extracted molten steel. Furthermore, the method using the SN plate vibration is effective for restarting after casting once, but for restarting after casting, but before starting casting,
The temperature of the plate is 100 ° C. at best, and the solidification of molten steel by vibration alone is not complete, and there is a drawback that the reliability is lacking.

[0004]

The object of the present invention is to provide an SN
It is an object of the present invention to provide means for surely preventing solidification of the extracted molten steel and making the initial casting start more reliable in the initial molten steel extraction using the plate.

[0005]

According to the present invention, there is provided a nozzle hole for casting molten steel by sliding movement of a sliding plate of a sliding nozzle device arranged at a lower position of an upper nozzle arranged at a bottom opening of a molten steel container. The object was achieved by the initial opening method, in which the stirring of molten steel by bubbling by gas injection into the molten steel in the nozzle hole and the intermittent sliding operation at the closed position of the sliding plate were used together.

When the molten steel agitation by bubbling and the intermittent operation of the sliding plate are used together, the intermittent operation time of the gas bubbling and the sliding plate is preferably 60 seconds or less because it leads to solidification of the molten steel.

In the intermittent operation, the operation stroke is 1 m.
It is preferable that the operation speed is 10 m / sec or more, and the stop time in the intermittent operation is 1 second or less.

When the gas bubbling amount is large, the molten steel is cooled and the molten steel is solidified, and even when the gas bubbling amount is small, the stirring is insufficient and the molten steel is solidified. Therefore, the gas bubbling amount is preferably 50 to 150 liters / minute. Further, if the gas bubbling pressure is low, the stirring ability will be lowered, so 1 kg / cm ² or more is desirable.

In this combined operation, if the bubbling is performed earlier than the start of the intermittent operation, the atmospheric temperature is lowered and the molten steel begins to solidify. Further, the intermittent operation of the sliding plate starts at the timing when the molten steel reaches the opening. It is desirable that this timing be within 10 seconds.

[0010]

When the casting is started, gas is blown into the molten steel (bubbling) to stir the molten steel before the casting is started to levitate foreign matters in the molten steel, and by vibrating the SN plate, the plate surface Prevent the molten steel pseudo solidification and its pseudo solid expansion.

During this combined operation, the molten steel has entered the SN plate, but due to the intermittent operation of the sliding plate, the molten steel near the upper nozzle and the fixed plate is vibrated, and the molten steel after floating the foreign matter , Held on the upper surface of the sliding plate in a completely molten state.

Intermittent operation of the sliding plate prevents molten steel pseudo-solidification near the plate surface, and bubbling stirs molten steel near the bubbling blow surface (inside the nozzle hole) to make the molten steel temperature uniform and Although solidification is prevented, the adoption of only one of them has only the effect of partially preventing molten steel from becoming pseudo-solidified. By using together, not only the entire molten steel accumulated in the nozzle hole including the vicinity of the plate surface is prevented from being pseudo-solidified but also sufficiently stirred, the molten steel temperature is made uniform, and a molten state capable of casting can be secured. Furthermore, it is expected that the quality of the steel will be kept constant by the sufficient stirring effect.

[0013]

1 shows an apparatus for carrying out the invention and its operating condition.

In FIG. 1, reference numeral 1 denotes a casting device provided at the bottom of the molten steel container 2, which comprises an upper nozzle 3, a sliding nozzle device 4 and sliding plates 41, 4.
2, the lower nozzle 5, and the immersion nozzle 6 are arranged in this order.
On the inner surface of the upper nozzle 3 and the inner surface of the upper plate 41, gas injection ports 7 made of porous or fine holes are regularly arranged and formed in contact with molten steel. Further, the sliding nozzle device 4 includes an upper and lower fixed plate 41 and a sliding plate 4 arranged in the middle thereof.
2 and a driving cylinder to which the sliding plate 42 is connected, the sliding speed, the sliding stroke, and the stop time are adjustable.

When the casting apparatus 1 is operated in a closed position where molten steel does not flow out during the initial casting of molten steel, the sliding speed is 30 mm / sec, the sliding stroke is 15 mm, and the stopping time is 1.
The periodic intermittent operation of the sliding plate with a period of 2 seconds and a period of 2 seconds, and 100 liters of gas into the molten steel from the gas injection port 7 opening to the upper inner surface of the upper nozzle 3 and the fixed plate 41.
The bubbling which introduces the amount was used together.

Intermittent operation of the sliding plate was started at almost the same timing as this gas bubbling, and the operation was completed within 60 seconds.

By this operation, while the molten steel in the nozzle hole floats the foreign matter, the molten steel which is completely melted in the nozzle hole by vibration is held by the upper surface of the sliding plate and the sliding plate opens. After moving to the state of 100, 100% casting could be started without the molten steel solidifying.

For comparison, the above operation was performed only by bubbling and only by intermittent operation of the sliding plate. The success rate of each opening was 80% and 50%.

The results are shown in Table 1.

[0020]

[Table 1] In the above embodiment, gas is blown into the molten steel through the upper nozzle 3 and the gas blowing port provided on the inner surface of the fixed plate 41. However, this gas blowing is performed through the molten steel outlet hole. By performing the operation from the inside of the vicinity toward the surface of the sliding plate 42 below, the dead space around the molten steel outflow hole at the time of bubbling can be completely removed by the gas leaking from between the plate surfaces, and the plate sliding The surface itself can be protected by an inert gas and the sliding resistance can be reduced.

[0021]

The present invention has the following effects.

(1) Since the solidification prevention surface is biased only by a single operation, the success rate of opening is low, but when bubbling and intermittent sliding are used in combination, the sliding surface and the nozzle hole surrounding surface where solidification of molten steel begins Can be prevented by intermittent sliding of the bubbling and the sliding plate, respectively.

(2) By using the intermittent sliding operation and the bubbling together, bubbles in the bubbling are subdivided, so that defects in steel due to the bubbling are not increased.

(3) In the initial opening state, most of the foreign matters which become the defect products in the steel are deposited near the closed sliding surface of the lower part of the nozzle. The foreign matter deposited and deposited on the bottom of the nozzle hole is removed. At the same time as the sliding plate is peeled from the sliding surface by the intermittent sliding operation, it is levitated by the bubbling gas, so that the foreign matter levitating effect is increased, and as a result, defects in the steel are reduced.

(4) A reliable initial casting opening that does not require tools such as filling material for casting start, fireproof or metallic start tube, and stable casting start,
It enables automatic operation of the entire casting process using the sliding nozzle device.

(5) It is possible to sufficiently stir the molten steel low temperature portion just above the sliding plate and the nozzle hole during solidification and the high temperature portion at the center of the nozzle hole, and to make the molten steel temperature at the start of casting uniform. Molten steel can be discharged at a constant flow rate.

(6) Stir the molten steel before the start of casting,
It has the effect of levitating the foreign substances in the molten steel and brings good results to the quality of the steel.

(7) The required amount of gas can be reduced as compared with the case of only bubbling.

(8) Due to the bubbling effect, foreign matter at the start of casting can be floated and foreign matter can be prevented from entering the mold.

[Brief description of drawings]

FIG. 1 shows an apparatus for implementing the present invention.

[Explanation of symbols]

1 Casting Device 2 Molten Steel Container 3 Upper Nozzle 4 Sliding Nozzle Device 5 Lower Nozzle 6 Immersion Nozzle 7 Gas Injection Port 8 Drive Cylinder 41 Fixed Plate 42 Sliding Plate 9 Molten Steel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaaki Yamazaki Inventor Masaaki Yamazaki 1-1, Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Kurosaki Ceramics Co., Ltd.

Claims (1)

[Claims] 1. A method of initial opening of nozzle holes for casting molten steel by sliding movement of a sliding plate of a sliding nozzle device arranged at a lower position of an upper nozzle arranged at a bottom opening of a molten steel container, An initial opening method in molten steel casting in which molten steel agitation by bubbling by gas injection into molten steel in a nozzle hole and intermittent sliding motion at a closed position of a sliding plate are used together.