JPH08224660A - Method for preventing flowing-out of slag - Google Patents

Abstract

PURPOSE: To prevent the flowing-out of slag by giving rotating movement to molten metal in a cylinder at the bottom part of a vessel, measuring the molten metal surface level from the back pressure of inert gas blown from a porous refractory, etc., on the cylindrical wall surface and closing a sliding nozzle. CONSTITUTION: The rotating movement is given to the molten metal in a molten metal surface height measuring instrument 15 arranged at the bottom part of a ladle 7 with an electromagnetic stirring coil 1, and the inert gas 3 is blown from the ladle wall through a porous plug or a nozzle having many fine holes. The gas bubbles 8 are accumulated to near the center with a blowing gas centrifugal separator 2 and after floating up the gas bubbles, new molten metal is changed into the molten metal surface height measuring instrument 15. At this time, the molten metal surface height 10 is judged from the back pressure of the blown inert gas 3 continuously measured with a back pressure measuring instrument 4. When the molten metal surface 13 reaches the ladle bottom 9, the sliding nozzle 5 arranged in a long nozzle 6 is closed to prevent the flowing- out of the slag. By this method, the clean molten metal can be supplied into the solidifying process.

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 outflow of slag when a molten metal is moved from a container containing the slag and the molten metal to a container for the next step in a steelmaking plant.

[0002]

2. Description of the Related Art In recent years, requirements for material properties of thin plate materials for automobiles and home appliances, and offshore structures, storage tanks, steel pipes for transporting oil and gas, high-strength wire rods and the like have become more severe. On the other hand, the solidification process has been remarkably developed in recent years, and most of the products are manufactured by the continuous casting method, and the near net shape technology such as the strip casting method is also being developed.

In these manufacturing processes, the molten metal is usually smelted and melted in a converter, an electric furnace, a high-frequency furnace, etc., and the smelted and melted metal moves to a pan. The molten metal inside is distributed to each mold. In the operation of moving these melts, it is difficult to completely separate the slag, and especially when looking at the tundish process from the pot, the pot slag flows out into the tundish, and for example, if the surface defects of thin plates are estimated from its composition, the pot is Inclusions considered to be slag have been observed in some cases, and the outflow of pot slag to tundish increases the oxidizing ability of slag in tundish, causing fine inclusions in tundish.

Therefore, prevention of outflow of pan slag is an important technical issue. As a method for preventing the outflow of ladle slag, the magnetic force generating coil and the receiving coil are provided in the molten metal discharge hole in the 127th Nishiyama Memorial Technical Lecture, and the current value generated in the receiving coil is the case where the fluid flowing through the discharge hole is the molten metal. A method of operating the nozzle opening by utilizing the difference in the case of slag is well known. However, in the case of this method, if the size of the slag caught in the molten metal passing through the discharge hole does not reach a certain level, a clear difference does not appear in the signal generated in the receiving coil, and the slag is not completely prevented from flowing out.

[0005]

Therefore, in order to completely prevent the outflow of the pan slag discharged from the pan, it is an important subject to establish a method for accurately measuring the timing of the outflow of the slag.

[0006]

The gist of the present invention is as follows. (1) In a method of separating a slag and a molten metal from a container in which the slag and the molten metal are placed, when the molten metal is moved to another container, a cylindrical tube is provided at a lower portion of the container, and the molten metal has a cylindrical wall. Injecting an inert gas from a cylindrical wall surface through a porous refractory or one or more nozzles while giving a vertical rotational motion, and based on the change in back pressure of the inert gas, A slag outflow prevention method that measures the height and operates the sliding nozzle opening, stopper opening and tilting angle to separate molten metal and slag.

[0007]

[Operations and Examples] FIG. 1 shows a molten metal level measuring device 15 of the present invention.
2A is an explanatory view of a plane, and FIG. 3B is an explanatory view of a vertical section of YY. FIG. 2 shows an example in which the device 15 is attached to the pan 7. A porous plug having a large number of holes or one or more nozzles 11 is provided by rotating the molten metal in the apparatus 15 provided in the lower portion of the pan 7 by the electromagnetic stirring coil 1 while rotating the molten metal.
The inert gas 3 is blown from the furnace wall 14 by the above, and the bubbles 8 blown by the blown gas centrifugal separation unit 2 are accumulated in the vicinity of the center. Prevent temperature drop.

At this time, as a result of continuously measuring the back pressure of the inert gas blown by the back pressure measuring device 4, the back pressure of the blown inert gas was determined as the molten metal was discharged from the pan to the tundish. The present invention has been accomplished by finding that it gradually decreases without changing.

FIG. 3 shows an example of the present method in which the molten metal is rotated and the gas is blown, and the change in back pressure with time when the molten metal is not rotated is measured. In the case of this method in which gas is blown while imparting rotational motion to the molten metal, the back pressure of the blown gas decreases linearly, whereas when gas is blown without imparting rotary motion, the gas back pressure is linear. There is a tendency for the back pressure to remain constant or to increase without decreasing. When the rotation is not applied, the back pressure does not decrease linearly because the temperature inside the device 15 drops or the holes for gas injection are clogged by inclusions or the like.

FIG. 4 shows the relationship between the back pressure of the blown inert gas measured by the back pressure measuring device 4 and the measured molten metal height 10.
In the case of this method in which gas is blown into the rotating molten metal, the back pressure of the blown gas has a good correlation with the molten metal height 10, and the molten metal surface height 10 remaining in the pan is accurately measured. it can. The height of the molten metal surface in FIG. 4 was measured by dropping the lance in which the electrode was inserted into the pot and moving the electrode from the reference when the current flowed.

FIG. 5 shows the back pressure of the blown inert gas as shown in FIG.
Thus, the relationship between CaO and the number of castings when the sliding nozzle 5 provided in the long nozzle 6 is closed when the molten metal level 13 is measured and the molten metal level 13 reaches the pot bottom 9. In the case of the conventional method, the CaO concentration not contained in the tundish slag gradually increases as the number of castings increases, whereas in the present method, the increase of the CaO concentration is small and the slag outflow can be prevented.

[0012]

As described above, according to the method for determining the level of the residual molten metal proposed in the present invention, it becomes possible to accurately grasp the timing when the sliding nozzle of the pan is closed, and to supply a clean molten metal to the solidification process. It became possible to do. This method can be applied not only to the pan to the tundish but also to a method of separating the molten metal and the slag when the molten metal is moved from the refining furnace to the pan.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of the present apparatus.

FIG. 2 is a diagram showing a method of installing the device.

FIG. 3 is a diagram showing the stability of a blown inert gas back pressure in this method.

FIG. 4 is a diagram showing a relationship between back pressure of an inert gas blow and height of a molten metal surface.

FIG. 5 is a view showing the pot slag outflow prevention effect of this method.

[Explanation of symbols]

1: electromagnetic stirring coil 2: blown gas centrifugal separation part 3:
Inert gas 4: Back pressure measuring device 5: Sliding nozzle 6: Long nozzle 7: Pan 8: Bubble 9: Pan bottom 10: Hot water level 11: Porous or pipe-shaped inert gas blowing nozzle 12: Slag 13: Molten metal surface 14: Furnace wall 15: Molten metal level measuring device of the present invention.

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Claims (1)

[Claims] 1. From a container containing slag and molten metal,
In the method of separating slag and molten metal when moving the molten metal to another container, a cylindrical tube is provided in the lower part of the container, and while the molten metal is subjected to a rotary motion perpendicular to the cylindrical wall, Injecting inert gas with a refractory or one or more nozzles, and measuring the height of the surface of the remaining molten metal in the container based on the change in the back pressure of the inert gas, sliding nozzle opening and stopper opening And a slag outflow prevention method that separates molten metal and slag by operating the angle of tilting.