JPH11104797A - Prevention of molten slag flow and its interface detecting electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pour the molten metal without generating the outflow of the molten slag. SOLUTION: In this preventing method, an electrical conductivity of a molten member composed of the molten slag 2 and the molten metal 3 is measured by the electrodes of a ladle and tundish. This makes it possible to detect an interface 9, which is the interface between the molten slag 2 and the molten metal 3 and moves along with the pouring of the molten steel 3 from the ladle. Then, a pouring nozzle 6 is closed before the time when the pouring of the molten metal from the ladle is finished, being obtained by adding the detected time and the time corresponding to the position of the ladle electrode and the pouring speed of the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing molten slag in a ladle from flowing out to a tundish when a molten steel is poured from a ladle into a tundish in continuous casting of steel. The present invention relates to a slag interface detection electrode.

[0002]

2. Description of the Related Art When pouring molten steel from a ladle into a tundish, molten slag in the ladle that forms a separate layer from the molten steel and floats on the molten steel remains in the ladle and flows out to the tundish. It is important not to let them. For this purpose, the following method is generally used.

[0003] In order to detect the change in brightness in the flow of molten steel from the ladle to the tundish, a space is provided for monitoring the flow of ladle between the ladle and the tundish.
The observer can visually monitor the outflow, or install an emissivity meter for luminance measurement toward the outflow,
Detects a change in the brightness of the pouring flow when changing from the pouring flow of molten steel to the pouring flow containing molten slag. Then, when a change in the brightness of the pouring flow occurs, the pouring nozzle of the ladle is closed to prevent excess molten slag from flowing into the tundish.

[0004] Electromagnetic detection, in which a transmitting coil and a transmitting coil are arranged at a pouring port of a ladle and detects a change in magnetism caused by mixing of molten slag into the molten steel pouring flow, is based on electromagnetic detection. The detection of the outflow of the molten slag occurs only when the ratio is exceeded. (For example, Japanese Patent Publication No. Sho 62-500646)

[0005] Japanese Patent Application Laid-Open No. 62-83 discloses electrical resistance type detection.
No. 415 discloses a method for tapping steel from a converter, which continuously measures the electrical resistance between the tapping hole of the converter and an electrode installed in a ladle to detect that molten slag has flowed out. I do.

[0006]

However, all of the conventional techniques are aimed at detecting the outflow of molten slag, and when the outflow of molten slag exceeds a certain amount, it is first detected as outflow of molten slag. The outflow of molten slag to molten steel cannot be completely eliminated. That is, it was not intended to grasp the state of decrease in the amount of molten steel in the ladle to prevent outflow of molten slag.

In the electric resistance type detection, there is also a problem that the electrodes connected to the molten slag and the molten steel are not melted due to high temperature, and the electric conductivity cannot be measured stably.

[0008] The above is not limited to the pouring of molten steel from a ladle into a tundish in continuous casting, but rather from the melting vessel containing a molten material composed of molten slag and molten metal. Also occurs when only molten metal is poured out.

[0009]

According to the present invention, the electric conductivity of a melt composed of molten slag and molten steel is measured by using a ladle electrode (first electrode) and a tundish electrode (second electrode).
By detecting the interface between the molten slag and the molten steel, which moves with the pouring of the molten steel from the ladle, the time of the detection is determined.

Then, the time determined by the position of the electrode (first electrode) in the ladle and the pouring speed of the molten steel is defined as:
The time added to the time when the interface between the molten slag and the molten steel is detected is the completion time of the pouring of the molten steel from the ladle. Prior to its completion time, the dispensing nozzle is closed. As a result, the molten slag can be prevented from flowing out of the ladle, so that the molten slag does not mix with the molten steel of the tundish.

The molten slag interface detection electrode is a linear electrode installed on the inner surface of a wall of a ladle or a tundish, or both.

The molten steel contained in the ladle or the tundish, or both, penetrates and fills the concave space provided on the inner surface of the wall, thereby forming an electrode integrated with the existing linear electrode. Useful. It is desirable that the maximum cross-sectional area of the electrode in the portion filled with the concave space is 20 mm ² or more, and the length of the electrode is 40 mm or more. It is also useful that the block forming the concave space is electrically insulated from the wall constituting the ladle or the tundish and has low permeability to molten steel.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The interface between molten slag and molten steel, which moves with the pouring from the ladle, is detected, and the molten slag is moved before the completion of the pouring of molten steel from the ladle. Prevent from flowing out. Hereinafter, a specific example of the present invention will be described with an example in which molten steel is poured out in continuous casting.

FIG. 1 is a sectional view of an apparatus used in a method for preventing molten slag from flowing out, showing a ladle 1 and a first ladle provided on the ladle.
Of the molten slag 2 in the ladle 1 composed of the iron shell 12 and the refractory 11, comprising the electrode 4, the detection device 5, the pouring nozzle 6, the tundish 7, and the second electrode 8 provided on the tundish. , Molten steel 3 is present.

The pouring nozzle 6 is opened to pour the molten steel 3 into the tundish 7. Then, the molten steel 3 is poured into the mold 10 while leaving an appropriate amount of the molten steel 3 in the tundish 7 to form a continuous ingot.

The molten steel 3 is poured from the ladle 1 to the tundish 7 and the interface 9 between the molten slag 2 and the molten steel 3 in the ladle 1 descends. The passage of the position of the interface 9 through the ladle internal electrode 4 is detected by a change in electric conductivity measured between the first electrode 4 and the second electrode 8.

That is, the refractory 1 in the steel shell 12 of the ladle 1
1 is connected to only the molten steel 3 at the initial stage of pouring the molten steel 3 from the ladle 1 to the tundish 7, so that the first electrode 4 and the first electrode 4 are connected to the first electrode 4. The electric conductivity of only the molten steel 3 is detected between the two electrodes 8 (FIG. 1).
However, the pouring of the molten steel 3 from the ladle 1 to the tundish 7 progresses, and the interface 9 between the molten slag 2 and the molten steel 3 descends.
When the connection changes from the molten steel 3 to the molten slag 2 at the electrode 4 of FIG. 2 (FIG. 2), the electrical conductivity measured between the first electrode 4 and the second electrode 8 changes at the moment of the change. .

By this change, the molten slag 2 and the molten steel 3
At the time when the interface 9 is detected, the time until the interface 9 reaches the bottom of the ladle, which is determined from the amount of molten steel remaining in the ladle and the pouring speed of the molten steel 3, is determined. In addition, before the time when the pouring of the molten steel 3 from the ladle 1 is completed, the pouring nozzle 6 at the bottom of the ladle 1 is closed to prevent the molten slag 2 from flowing out of the ladle 1 to the tundish 7. can do.

Further, by disposing electrodes (for example, two electrodes 4 and 4-1 as shown in FIG. 1) at a plurality of positions in the ladle 1 in the height direction, the molten steel 3 can be melted and discharged. It is possible to detect a descent of the interface 9 between the slag 2 and the molten steel 3, that is, a decrease in the amount of the molten steel 3 in the ladle 1.

When each electrode in the ladle is connected to the molten slag, the measured electric conductivity decreases, and the interface drop from the electrode installed in the upper part of the ladle to the lower electrode in order from the lower electrode. That is detected. Each detection time,
Immediately before the end time of the pouring of the molten steel calculated from the installation position of the electrode in the ladle and the pouring speed of the molten steel, the pouring nozzle 6 is closed, and the outflow of the molten slag from the ladle 1 to the tundish 7 is performed. To prevent.

It is also effective to use a direct current as a current for measuring the electric conductivity. In general, it is known that molten slag 2 exhibits ionic conductivity and thus causes polarization. It is desirable for the measurement of the electrical conductivity that the difference between the electrical conductivity of the molten slag 2 and the electrical conductivity of the molten steel 3 is large. When a current is applied to the molten slag 2 using a DC current, the molten slag 2 is polarized. Thus, the interface 9 between the molten slag 2 and the molten steel 3 can be clearly detected.

FIG. 3 shows a measurement example of the present invention between one electrode 4 installed on the ladle 1 and an electrode 8 installed on the tundish 7 (connected to the molten steel 1 in the tundish 7). 3 shows a change in electrical conductivity. The vertical axis corresponds to the voltage (V), and the vertical axis corresponds to a measurement time of 72 seconds on one scale.

In the situation where the electrodes 4, 4-1, 8 are connected only to the molten steel 3 without molten slag in the initial to middle stages of pouring the molten steel 3 into the tundish 7, the measured electric conductivity is It is stable. It was checked whether the measured value was stable and whether the measured value showed a measured value corresponding to the electrical conductivity of molten steel. As a result, it was confirmed that no problem such as disconnection occurred in the electrodes and the like. After that, the measurement of the present invention was performed.

While the electrode 4 is connected to the molten steel 3 (FIG. 1)
The electric conductivity shown in FIG. 3 is a value corresponding to the electric conductivity of the molten steel 3 ((a) in FIG. 3), and with the pouring of the molten steel 3 from the ladle 1 to the tundish 7, The interface 9 between the molten slag 2 and the molten steel 3 is lowered, and the molten slag 2 is connected to the electrode 4 and at the same time, the electrical conductivity is reduced. ((B) in FIG. 3)

Further, after a lapse of time determined by the electrode installation position in the ladle and the molten steel pouring speed, the pouring nozzle 6 of the ladle was closed. Here, since the discharge flow disappears, the electric conductivity becomes zero. ((C) in FIG. 3)

[0026]

According to the present invention, the molten steel in the ladle can be poured into the tundish without causing the molten slag to flow out, without relying on monitoring relying on human attention. There is little impossibility of measuring electrical conductivity such as disconnection of electrodes connected to the melt,
Enables stable measurement.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus used in a method for preventing molten slag from flowing out.

FIG. 2 is a view showing a final stage of pouring molten steel from a ladle in FIG.

FIG. 3 is a diagram showing a measurement example of a change in electric conductivity.

[Explanation of symbols]

 1: Ladle 2: Molten slag 3: Molten steel 4: Electrode in ladle 4-1: Another electrode in ladle 5: Detection device: Pour nozzle 7: Tundish 8: Electrode in tundish 9: Molten slag 10: Mold 11: Refractory 12: Iron skin

Claims (2)

[Claims] An electric conductivity of a molten steel contained in a ladle and a molten slag floating on an upper portion of the molten steel is measured by a first electrode provided on an inner surface of a wall of the ladle; It is measured between a second electrode provided on the inner surface of the wall of the tundish containing the molten steel poured from the bottom, and the electric power of the molten steel when the interface between the molten slag and the molten steel passes through the first electrode. A change in conductivity is detected, and the time when the change is detected is added to the ladle capacity at the first electrode position and the time required to reach the ladle bottom at the interface determined from the molten steel pouring speed. ,
The molten slag is prevented from flowing out of the ladle by closing a pouring nozzle provided at the bottom of the ladle before the time at which the molten steel is completely poured out from the ladle. Method. 2. The molten steel contained in the ladle or the tundish, or both, penetrates and fills the concave space provided on the inner surface of the wall, thereby integrating with the existing linear electrode. An electrode for detecting a molten slag interface, wherein an electrode is formed.