KR101052265B1 - Control method of discharge amount of tundish nozzle - Google Patents

Abstract

A method of controlling the discharge amount of the tundish nozzle, which improves the product quality by preventing the occurrence of dead zones, which are the stagnant molten steel zones generated in the tundish nozzle, and improves the efficiency of the continuous casting operation, is introduced. In the tundish nozzle discharge amount control method of the present invention, the upper and lower portions of the intermediate plate is fixed between the upper plate 24 fixed to the bottom side of the tundish T and the lower plate 26 fixed to the immersion nozzle 10 side. The opening of the molten steel inlet (24a) formed in the upper plate 24 and the molten steel inlet (26a) formed in the lower plate 26 while drawing a circular trajectory with respect to the plate (24,26), the intermediate plate 28 Is characterized in that the rotation at least 0.1 times per minute or less.

Tundish, Nozzle, Opening, Rotation, Intermediate Plate

Description

TECHNICAL FOR CONTROLLING THE QUANTITY OF MOLTEN STEELDISCHARGED THROUGH TURNDISH NOZZLE}

The present invention relates to a method for controlling the discharge amount of the tundish nozzle, and more particularly, the discharge amount of the tundish nozzle which minimizes the generation of dead zone, which is a molten steel stagnant area generated by the intermediate plate of the tundish nozzle constantly moving only in the transverse direction. It relates to a control method.

In general, liquid molten steel refined through the steelmaking process is made of intermediate materials such as slabs, blooms, billets, etc. In this process, the molten steel refined in the steelmaking process is moved to the state contained in the ladle and stored in the tundish T shown in FIG. 1, and the molten steel stored in the tundish T is supplied to a mold (not shown). Molten steel stored in the tundish (T) for continuous casting must be supplied to the mold to solidify the molten steel of the liquid while maintaining a constant amount until the end of the continuous casting process. The amount of molten steel supplied to the mold in the tundish T by a function of time is called a discharge amount, and the discharge amount is controlled by the operator's intention to improve the final quality of the product.

As a method of controlling the discharge amount of the molten steel, there are a sliding gate type and a stopper type. Sliding gate type which is generally used in recent years can be divided into two piece type (three piece type) and three piece type (three piece type). In the former case, the position of the immersion nozzle is controlled beyond the center of the mold Recently, the latter three-piece type is mainly used.

A method of controlling the discharge amount of molten steel by the sliding gate type will be described. As illustrated in FIG. 2, an upper nozzle 2a is installed at the bottom of the tundish T so that molten steel may flow out through the bottom of the tundish T. On the outer bottom surface of the tundish T, an upper plate 2b having a hole through which molten steel passes is fixedly installed, and a hole through which molten steel passes is also formed on the side of the immersion nozzle 1 for supplying molten steel to a mold (not shown). The lower plate 2d is fixedly installed. An intermediate plate 2c is installed between the upper plate 2a and the lower plate 2d, and holes are also formed in the intermediate plate 2c. The intermediate plate 2c adjusts the opening degree of the holes formed in the upper and lower plates 2b and 2d, respectively, while moving only in the lateral direction between the upper plate 2b and the lower plate 2d.

In the case of adjusting the opening degree of the holes formed in the upper and lower plates 2b and 2d while the intermediate plate 2c is constantly moving only in the transverse direction (see FIG. 3) with time, the stagnant region of the molten steel between the plates Dead zone (D) is generated.

That is, the molten steel supplied through the upper nozzle 2a at the beginning of continuous casting is in contact with the inner wall of the upper nozzle 2a, and the temperature of the molten steel decreases, so that the molten steel solidifies on the inner wall of the upper nozzle 2a, and the continuous casting proceeds. As a result, the deposit S grows between the upper and lower plates 2b and 2d and the intermediate plate 2c to form a dead zone D, which is a stagnant region of the molten steel. When the dead zone (D) is formed, the openings of the upper and lower plates (2b, 2d) should be expanded, as well as the attachments using Ar to remove the deposits (S) formed in the dead zone (D). Pressure is applied to S). At this time, when the deposit (S) dropped from the dead zone (D) flows into the molten steel, it may cause product defects. If the deposit (S) is continuously accumulated in the dead zone (D), an immersion nozzle is formed. The molten steel flow in (1) will be uneven. That is, drift in which molten steel discharged to the immersion nozzle 1 is biased to one side is generated, which causes waves in the molten steel molten surface of the mold. The wave generated in such molten steel surface causes a cast iron defect. In addition, since separate work is required to remove deposits in the dead zone (D) generation region, workability of the continuous casting process may be deteriorated.

Various studies have been conducted to prevent the occurrence of dead zones (D), which are stagnant regions of molten steel, and a method of giving a taper to the plate, a method of dividing the plate into four pieces, and controlling each of them. Although it is proposed, a method of solving the dead zone of the molten steel structurally easy and yet has not been proposed.

The present invention to solve the conventional problems, the intermediate plate sliding between the upper plate and the lower plate draws a circular trajectory and adjusts the openings of the molten steel outlet and the molten steel inlet through which the molten steel passes through the attachments generated in the tundish nozzle The purpose of the present invention is to provide a method for controlling the discharge amount of a tundish nozzle, which minimizes the clogging problem of the tundish nozzle and the quality degradation of the product due to the drift of molten steel.

Discharge amount control method of the tundish nozzle according to the present invention for achieving this object is the molten steel passing through the upper nozzle formed on the bottom of the tundish is supplied to the mold through the immersion nozzle and fixed to the bottom side of the tundish and In the discharge amount control method of the discharge amount of the tundish nozzle to control the discharge amount of the molten steel by using the intermediate plate sliding between the lower plate fixed to the immersion nozzle side, the intermediate plate draws a circular trajectory with respect to the upper and lower plates The opening degree of the molten steel inlet formed in the upper plate and the molten steel inlet formed in the lower plate is adjusted, and the intermediate plate rotates at least 0.1 times per minute or less.

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In addition, the intermediate plate is characterized in that it moves continuously from the beginning of the play process to the end of the play process.

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The present invention prevents the occurrence of dead zones in the tundish nozzle by suppressing the molten steel stagnant region generation of the tundish nozzle due to the above technical configuration. When the dead zone is prevented, the molten steel can be prevented from being drifted, and the amount of Ar added excessively to remove the deposits present in the dead zone can be minimized. In addition, a stable hot water level can be expected in the mold, so that a good quality product can be produced. Furthermore, the clogging problem of the tundish nozzle is improved, so that the number of annual performances can be increased by not having to go through a separate work process due to the clogging, thereby improving work efficiency.

Hereinafter, with reference to the accompanying drawings looks at the tundish nozzle discharge amount control method according to a preferred embodiment of the present invention. First, the discharge amount control device of the tundish nozzle of the present invention will be described, and then the control method of such a device will be described.

As shown in Figure 4, the discharge amount control device of the tundish nozzle 20 according to the present invention is an immersion for supplying the molten steel to the mold (not shown) from the tundish (T) containing the refined molten steel made in the steelmaking process And a tundish nozzle 20 positioned between the nozzle 10 and the tundish T and the immersion nozzle 10 to adjust a supply amount of molten steel. The tundish T stores liquid molten steel in a predetermined amount until the end of continuous casting, and continuously supplies liquid molten steel to the mold through the immersion nozzle 10. The immersion nozzle 10 has a hole formed in the longitudinal direction in the molten steel to pass through it.

The tundish nozzle 20 is installed between the tundish T and the immersion nozzle 10. The tundish nozzle 20 is installed on the bottom of the tundish T and is disposed on the outer side of the upper nozzle 22 and the bottom of the tundish T for discharging molten steel in the tundish T to the outside of the tundish T. It is fixedly installed but fixedly coupled to the upper end of the upper plate 24 and the immersion nozzle 10 through which the molten steel outlet 24a is formed to pass through the molten steel discharged from the upper nozzle 22 and formed on the upper plate 24. Upper and lower portions of the lower plate 26 and the tundish T and the immersion nozzle 10 each having a molten steel inlet 26a therethrough so that the molten steel having passed through the molten steel outlet 24a flows into the immersion nozzle 10. It includes an intermediate plate 28 for adjusting the opening degree of the molten steel inlet 24a and the molten steel inlet 26a formed through the upper and lower plates 24 and 26, respectively, while moving between the plates 24 and 26. The intermediate plate 28 is formed with a constant opening degree opening 28a corresponding to the molten steel outlet 24a and the molten steel inlet 26a formed on the upper and lower plates 24 and 26, respectively.

The driving means 30 is coupled to one side of the intermediate plate 28. The driving means 30 provides a driving force to allow the intermediate plate 28 to slide between the upper and lower plates 24 and 26 while drawing a circular trajectory. That is, the intermediate plate 28 rotated by the driving means 30 is rotated while drawing a circular trajectory, the molten steel outlet 24a and the molten steel inlet 26a formed in the upper and lower plates 24 and 26, respectively. And since the molten steel is passed through only the portion through which the opening adjustment mechanism (28a) formed in the intermediate plate 28 is matched, the discharge amount of the molten steel supplied to the mold from the tundish (T) can be controlled. Since the intermediate plate 28 rotates and moves in all directions, no dead zone is generated because the intermediate plate 28 is moved only in a predetermined direction. The driving means 30 may be applied in various forms. That is, the driving means 30 may be determined by a designer, such as a mechanical method using a gear or the like, a hydraulic method or an electric method in consideration of design convenience, economy, and safety.

Hereinafter, the method for controlling the discharge amount of the tundish nozzle of the present invention will be described.

As shown in FIGS. 4 and 5, the intermediate plate 28 draws a circular trajectory with respect to the upper and lower plates 24 and 26, and the molten steel outlet 24a formed in the upper and lower plates 24 and 26, respectively. ) And the opening degree of the molten steel inlet (26a). In order to increase the amount of molten steel supplied to the mold through the immersion nozzle 10 from the tundish T, the molten steel outlet 24a and the molten steel inlet 26a and the opening control unit 28a should be matched as much as possible. On the other hand, in order to reduce the supply amount of molten steel, the position of the opening control opening (28a) formed in the intermediate plate 28 is positioned as opposed to the molten steel outlet 24a and the molten steel inlet 26a as much as possible.

The intermediate plate 28 may be rotated by drawing a circular trajectory after being moved in a constant direction, but may also open the molten steel outlet 24a and the molten steel inlet 26a while being rotated from an initial stage.

On the other hand, a comparative experiment was conducted to investigate the most effective rotational speed of the intermediate plate 28. The most efficient rotational speed of the intermediate plate was measured by measuring the level of the water surface representing the difference between the top and bottom points of the molten steel surface flowing in the mold. The nozzle clogging index was calculated as (theoretical discharge flow rate of molten steel-the actual discharge flow rate of molten steel) / the actual discharge flow rate of molten steel. The result is as follows.

3 times / min

2 times / min
1 time / min
0.5 times / min
0.1 times / min
Once / 30min
Surface level (mm)

12
10
6
5
5
5
Nozzle Clogging Index

1.3
1.5
1.5
1.6
2.2
3.3

As shown in Table 1, the level of the hot water, which is an index indicating the flow stability of the molten steel in the mold, increases as the number of revolutions per minute of the intermediate plate 28 increases. This deteriorates the oil quality of molten steel and causes product defects. On the other hand, as the number of revolutions per minute of the intermediate plate 28 increases, the nozzle clogging index decreases to prevent the occurrence of drift in the tundish nozzle. Based on the comparative test data, Table 1, the level of the water surface is properly maintained to ensure the fluidity of the molten steel and at the same time, the number of revolutions of the intermediate plate 28 is limited to 0.1 or more per minute to prevent the molten steel from drifting. It is preferable to be.

When the number of revolutions of the intermediate plate 28 is maintained at less than 0.1 times per minute, it is possible to stably maintain the water level, but the nozzle clogging index is remarkably increased to prevent the occurrence of the dead zone region. In addition, when the number of revolutions of the intermediate plate 28 exceeds once per minute, the nozzle clogging index is maintained at an appropriate level, but the water level is significantly increased, resulting in product defects.

On the other hand, the intermediate plate 28 is preferably rotated from the beginning, as well as continuously rotated. Since the intermediate plate 28 is rotated while drawing a circular trajectory between the upper and lower plates 24 and 26 from the time when the molten steel is discharged from the tundish T, the upper and lower parts are stopped by stopping the intermediate plate 28. The formation of deposits that may occur between the plates 24 and 26 can be prevented.

By using the discharge amount control method of the tundish nozzle as described above, the generation of the dead zone area in the tundish nozzle is prevented, and the molten steel is prevented from being drift, thereby improving the product quality and increasing the working efficiency of the continuous casting process. .

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

1 is a schematic view showing a state in which molten steel is discharged through the tundish nozzle;

2 illustrates a dead zone formed in a tundish nozzle;

3 is a view showing a conventional intermediate plate movement trajectory;

4 is a view schematically showing a tundish nozzle discharge amount control apparatus of the present invention;

5 is a view showing the movement trajectory of the intermediate plate in the tundish nozzle discharge amount control method of the present invention.

[Description of Reference Numerals]

10: immersion nozzle 20: tundish nozzle

22: upper nozzle 24: upper plate

26: lower plate 28: intermediate plate

30: drive means T: tundish

D: Dead Zone S: Attachment

Claims (4)

Molten steel that passes through the upper nozzle formed on the bottom of the tundish is supplied to the mold through the immersion nozzle and is molten using an intermediate plate that slides between the upper plate fixed on the bottom side of the tundish and the lower plate fixed on the immersion nozzle side. In the discharge amount control method of the tundish nozzle for controlling the discharge amount of the The intermediate plate 28 draws a circular trajectory with respect to the upper and lower plates 24 and 26, and the molten steel inlet 24a formed in the upper plate 24 and the molten steel inlet 26a formed in the lower plate 26. And the intermediate plate 28 rotates at least 0.1 times per minute or less than once. delete The method according to claim 1, wherein the intermediate plate 28 is continuously controlled from the beginning of the playing process to the end of the playing process. delete

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