JPH06292951A - Method for completing pouring of molten steel in tundish and device therefor - Google Patents

Abstract

PURPOSE:To improve the casting yield by observing molten steel surface level in a mold, deciding the moment when the molten steel surface level is rapidly lowered as the time when pouring of the molten steel in a tundish into a mold completes, and closing a pouring nozzle. CONSTITUTION:At the casting end stage after inputting a signal for the completion of ladle pouring from an input device 13 for the completion of ladle pouring, in the case of detecting the fixed change rate or higher by calculating a molten steel surface level change rate with a detecting instrument 12 for calculating the molten steel surface level in a mold and rapidly lowering the molten steel surface level, an operating command is outputted to an alarming device 15 and a stopper driving control device 16 from the output device 14 for the completion of tundish TD1 pouring. Then, a stopper nozzle 2 is automatically closed through a stopper driving device 4 and a stopper supporting arm 3. By this method, the remaining molten steel in the TD is almost emptied and the flow-out of slag in the TD into the mold can surely be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for finishing casting of molten steel in a tundish (TD) into a mold in continuous casting of steel.

[0002]

2. Description of the Related Art In the continuous casting, the injection of the molten steel from the TD into the mold is generally completed by completely injecting the molten steel in the TD.
This is performed by closing the TD nozzle immediately after the D slag flows out into the mold. In this case, it is a basic condition to improve the casting yield and workability by injecting the molten steel in the TD without leaving it and minimizing the outflow amount of the TD slag.

In the conventional method, the amount of residual molten steel in the TD is grasped by measuring with a weighing machine such as a load cell or a measuring rod, and at the end of the final injection, the operator directly visually confirms the outflow of the TD slag into the mold. Is done by.

There is an error in these methods, and several tons of molten steel remains in the TD, or a considerable amount of T remains in the coin mold.
Since the D slag flows out, it takes a long time to reduce the casting yield and remove the slag in the mold, which is a problem.

[0005]

As described above, in the method in which the amount of residual hot water in the TD is grasped by a scale or a measuring rod, and the final injection is visually confirmed by the outflow confirmation of the TD slag. , TD is easily affected by the metal attached to the inner wall and residual slag.

[0006] Moreover, since the powder for casting is present on the surface of the molten steel in the mold with a thickness of several tens of mm, it is difficult to visually confirm even if the TD slag flows out. Therefore, the operator confirms the slag pouring out. Since it takes a considerable operating time to close the TD nozzle, there is a problem that a large amount of TD slag easily flows out into the mold.

The outflow of a large amount of slag not only requires labor and time to remove the slag, but also when the molten steel in the first ladle is finished and the molten steel in the second ladle is subsequently cast in succession with different steel types, the seam of the slab is There is a risk that the slag caught in the part will cause a breakout.

In order to prevent the above problems, a method of intentionally leaving a part (several tons) of the molten steel in the first ladle in the TD and injecting the molten steel in the rear ladle into the TD for continuous casting ("TD hot water") In the mixed type different steel type continuous casting method "), different components are mixed in the TD in the case of different steel types, and a large amount of slabs of components that are not compatible with the first ladle and the second ladle ( There is a problem that occurs.

In order to solve the above-mentioned problems, it is necessary to establish a method and an apparatus for keeping the molten steel of the pan in the TD as little as possible and minimizing the outflow of the TD slag into the mold.

[0010]

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for solving the above problems.

That is, according to the present invention, in the final stage of casting after the molten steel injection from the ladle to the TD is completed, casting is performed while monitoring the indicated value of the level gauge in the mold, and the indicated value of the level gauge suddenly increases. It is a method and an apparatus for closing the tundish injection nozzle by judging that the injection of the molten steel from the TD into the mold is completed at the moment when the temperature falls.

An injection termination device according to the present invention is shown in FIG.
A detailed description will be given below with reference to the drawings. 1 is TD, 2 is a stopper nozzle, 3 is a stopper support arm, 4 is a stopper driving device, 5 is molten steel, 6 is TD slag, 7 is a dipping nozzle, 8 is a mold, 9 is a slab, 10 is a pinch roll, 1
1 is a level meter in the mold, 12 is a device for calculating the level in the mold and a device for detecting a rapid decrease in the level, 13 is a ladle injection end input device, 14 is a TD injection end output device, 15 is an alarm device, 16 is a stopper drive It is a control device.

The molten metal level meter used in the present invention may be any one having a high sensitivity and a high response, and a vortex type, a γ-ray type, a laser type or the like is preferable.

The input method to the ladle pouring end input device is input by the operator at the time when the molten steel pouring from the ladle to the TD is completed, or automatically by detecting the weight of the ladle or detecting the outflow of the ladle slag. It may be input manually.

FIG. 1 is a diagram showing a casting termination method "auto stop method" of the final charge of continuous casting according to the present invention.

That is, at the end of casting after the ladle pouring end signal is input from the ladle pouring end input device 13, the molten metal level calculation in the mold and the rapid molten metal level detection device 12 are performed.
When the level change rate of the molten metal surface is calculated and the rate of change above a certain level is detected, the TD injection end output device 14 outputs an operation command to the alarm device 15 and the stopper drive control device 16, and the stopper drive device 4 And a method of ending casting in which the stopper nozzle 2 is automatically closed via the stopper instruction arm 3.

In FIG. 2, when performing continuous casting of different steel types having different molten steel components using the same TD, the rate of change of the molten metal level is calculated by the molten metal level calculation device 12 at the end of casting of the ladle, and the molten metal level change rate is above a certain level. When the rate of change is detected, the TD injection end output device 14 outputs an operation command to the alarm device 15, the stopper drive control device 16, and the pinch roll drive control device 17 to automatically close the stopper nozzle 2. At the same time, the withdrawal of the slab 9 is temporarily stopped, then an operation command is output to the ladle nozzle drive control device 18, and the molten steel in the rear ladle 20 is started to be injected into the TD 1 by the ladle nozzle drive device 19 and the mold 8
A continuous casting method of different steel types in which the injection into the slab and the withdrawal of the slab 9 are restarted is shown. This method is a "continuous casting method of different types of steel mixed in the mold"
Is.

Similar to FIG. 2, in FIG. 3, the stopper nozzle is closed based on the output of the operation command from the TD injection end output device 14, and the withdrawal of the cast piece is temporarily interrupted.
After inserting the sequence block 21 into the mold 8,
A continuous casting method of different steel types in which the injection of the molten steel into the TD is started, and the injection into the mold and the withdrawal of the slab 9 are restarted is shown. This method is "sequence block insertion type different steel type continuous casting method".

In the method shown in FIGS. 1, 2 and 3,
An operator manually performs a series of operations such as closing the stopper nozzle, stopping the pinch roll, ladle pouring, TD pouring, and slab withdrawal by an alarm output from the TD pouring end output device 14 to the alarm device 15. It is also possible.

[0020]

FIG. 4 shows an example of the change in the molten metal level in the mold (vortex flow level meter) measured by the inventors at the end of TD injection.

In the figure, it is clear that when the injection of the molten steel in the TD is completed, the value indicated by the molten metal level gauge in the mold drops sharply. This phenomenon is considered to occur due to the difference in the physical properties between the melt and the powder and the slag.

In both the casting termination method and the different steel type continuous casting method according to the present invention, compared with the conventional method, the molten steel in the TD can be completely cast into the mold without leaving at the same time, and at the same time, the TD slag flowing out into the mold is almost eliminated. You can control without any
Moreover, the reproducibility is high.

[0023]

EXAMPLE Steel for machine structural use was melted in a converter with a heat size of 270 tons / charge, and a slab having a cross-sectional size of 350 mm × 560 mm was cast by a curved continuous casting machine having a radius of curvature of 12 mR. A vortex flow level meter was used as the level gauge in the mold, and casting was performed by the method and apparatus of the present invention.

S45C as the first pot, SCM4 as the second pot
20 was continuously cast with different steel grades using a TD with a capacity of 30 tons, but S45C of the first ladle was cast at a casting speed of 0.70 m / min, and after pouring the ladle, it was made of low alloy steel (SCM4).
20) was placed on the ladle turret and the pan was replaced.

While carrying out the "Mixed-in-mold type different steel type continuous casting method (A method)" shown in FIG. 2 and the "Sequence block insertion type different steel type continuous casting method (B method)" shown in FIG. 3, respectively, For comparison, "TD inner molten metal mixed type continuous steel casting method" in which 3 tons of molten steel in the first ladle is left in the TD and the latter ladle is poured and mixed
I also went.

FIG. 5 shows a comparison of the lengths of the slabs at the seam joints of different steel types. According to the method of the present invention, the length of the seam of the cast slab is apparently short and the casting yield is high.

[0027]

According to the present invention, since the amount of residual hot water in the TD can be made almost zero, there is a great effect in reducing the seam piece length in continuous casting of different steel types and improving the casting yield.
Since it is possible to reliably prevent the outflow of the slag in the TD into the mold, it is extremely effective in stabilizing the operation.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a casting termination device of the present invention.

FIG. 2 is an explanatory view showing a continuous casting method for different steel types according to the present invention.

FIG. 3 is an explanatory view showing a continuous casting method for different steel types according to the present invention.

FIG. 4 is a diagram showing changes in the molten metal level at the end of TD injection.

FIG. 5 is a diagram showing the effect of the present invention.

[Explanation of symbols]

1 TD 2 Stopper nozzle 3 Stopper support arm 4 Stopper drive device 5 Molten steel 6 TD slag 7 Immersion nozzle 8 Mold 9 Cast slab 10 Pinch roll 11 Mold level gauge 12 Mold level calculation and melt level rapid drop detector 13 Ladle injection end input device 14 TD injection end output device 15 Alarm device 16 Stopper drive control device 17 Pinch roll drive control device 18 Ladle nozzle drive control device 19 Ladle nozzle drive device 20 Rear pan 21 Sequence block

Claims (2)

[Claims] 1. In the continuous casting of steel, after the molten steel injection from the ladle to the tundish is completed, the level of the molten metal in the mold is monitored and the moment when the molten metal level drops sharply A method for terminating molten steel injection in a tundish, which comprises closing the tundish injection nozzle upon determining that the injection into the mold is completed. 2. In a continuous casting facility for steel, means for inputting completion of molten steel injection from a ladle to a tundish, means for detecting a molten metal level in a mold, and molten metal detected by the means for detecting a molten metal level in the mold It consists of a means to detect that the surface level has dropped sharply and a control means to close the tundish injection nozzle.After the molten steel injection end signal from the ladle to the tundish is input, An apparatus for terminating molten steel injection in a tundish having a function of controlling to close a tundish injection nozzle when a rapid drop is detected.