JPH08224659A - Method for separating molten metal and slag - Google Patents

Abstract

PURPOSE: To prevent the flowing-out of slag by giving rotating movement to molten metal flow discharged from a vessel and floating up and separating gas bubbles, inclusion and the slag collected in the center part of the molten metal flow with the ascent of inert gas bubbles blown into the molten metal. CONSTITUTION: While giving the rotating movement to the molten metal with an electromagnetic coil 1, the inert gas 3 is blown from a porous plug or slit structural gas blowing refractory having many fine holes. In an inert gas blowing slag centrifugal separator 6, the gas bubbles 4, inclusions and ladle slag 12 are accumulated into near the center, and the floating-up and the separation of the inclusions and the ladle slag 12 are promoted by floating up the bubbles 4. The remained molten metal quantity in the vessel is measured based on the variation of back pressure of the blowing inert gas 3 measured with a back pressure measuring instrument 5, and the opening degrees of a sliding nozzle 7 and a stopper are operated to prevent the flowing-out of the slag. In such a way, the clean molten metal can be supplied into 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, demands 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, molten metal is usually refined and melted in converters, electric furnaces, high-frequency furnaces, etc., the molten metal that has been refined and melted moves to a pan, and the molten metal in the pan moves to a tundish, where the molten metal in the tundish Are distributed to each mold.

It is difficult to completely separate the slag in the operation of moving the molten metal. Especially, when looking at the tundish process from the pot, the pot slag flows out into the tundish, and for example, the surface defect of a thin plate is inferred from its composition. Then, there is an example in which inclusions that are considered to be pot slag are observed,
In addition, the outflow of pot slag to the tundish increases the oxidizing ability of the slag in the tundish, causing fine inclusions in the tundish. Therefore, prevention of outflow of pot slag is an important technical issue that has yet to be resolved.

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 Course, P185, and the current value generated in the examination coil is the fluid flowing through the discharge hole. A method of operating the nozzle opening degree by utilizing the difference between the case of slag and 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, it is an important issue to establish a method for completely preventing the outflow of slag when a molten metal is moved from one container containing the slag and the molten metal to another container.

[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 rotary motion perpendicular to the molten metal flow is applied to the molten metal at the molten metal outlet part While injecting an inert gas from the wall surface into the molten metal, centrifuging collects air bubbles, inclusions and slag in the center, and lifts air bubbles to float and separate them to prevent slag outflow. A method for separating molten metal and slag, which is characterized in that

(2) At the molten metal outflow portion of the container containing the slag and the molten metal, an inert gas is blown into the molten metal from the wall surface while imparting a rotary motion perpendicular to the molten metal flow to the bubbles by centrifugal separation. Accumulation of inclusions and pot slag in the center,
In the method of separating molten metal and slag that floats and separates them by rising bubbles, the amount of residual molten metal in the container is measured based on the change in the back pressure of the blown inert gas to determine the sliding nozzle opening and stopper opening. The method for separating molten metal and slag according to (1) above, which is operated to prevent the slag from flowing out.

[0008]

1 is a schematic view of the slag outflow prevention device of the present invention, and FIG. 2 is an example in which the device is attached to a pan 8. Injecting an inert gas 3 from a furnace wall 2 of a gas-blowing refractory having a porous plug or a slit structure having a large number of fine holes while rotating the molten metal with an electromagnetic stirring coil 1.
The bubbles 4, inclusions and pot slag 12 are accumulated in the vicinity of the center by the inert gas blown slag centrifugal separator 6, and the floating of the bubbles 4 promotes the floating separation of the inclusions and the pot slag 12.

At this time, the back pressure of the blown inert gas 3 continuously measured by the back pressure measuring device 5 does not change and gradually decreases as the molten metal is discharged from the pan 8 to the tundish. Based on the findings, the present invention has been accomplished. FIG.
Is a method of measuring the change of back pressure with time in the case where the molten metal is rotated and the gas is blown, and when no rotation is applied. In the case of this method in which gas is blown while imparting rotational movement to the molten metal, the back pressure of the blown gas decreases linearly, whereas when gas is blown without giving rotational movement, the gas back pressure is linear. There is a tendency for the back pressure to remain constant or to rise without increasing.

When the rotation is not applied, it is presumed that the back pressure decrease is not linear because the gas injection hole is clogged. FIG. 4 shows the relationship between the back pressure of the blown inert gas 3 measured by the back pressure measuring device 5 and the measured molten metal height 10. In the case of this method in which a gas is blown into the rotary molten metal, the back pressure of the blown gas has a good correlation with the molten metal height 10, and the amount of residual hot metal in the pan 8 can be accurately measured. The molten metal height was measured by dropping the lance into which the electrode was inserted into the pan and moving the electrode from the reference when the current flowed.

FIG. 5 shows that the slag 12 is prevented from flowing out by centrifugal separation of the blown inert gas, and the molten metal level 10 is measured from the back pressure of the inert gas 3 according to FIG. Thirteen
3 shows the relationship between the CaO concentration of the tundish slag and the number of castings in succession when the sliding nozzle 7 provided in the long nozzle 9 is closed when reaching the pot bottom 11. In the conventional method, the CaO originating from the pot slag 12, which was not included in the surface oxidation inhibitor to be added to the tundish, gradually increases and the pot slag 12 flows out, whereas in this method, an increase in CaO is almost observed. Therefore, it is understood that the pan slag 12 can be prevented from flowing out.

FIG. 6 shows an example of the relationship between the number of inclusions in the cast seam slab and the casting time. In the case of the conventional method, the inclusions in the seam slab greatly increase, whereas in the present method, the number of inclusions is stable at a lower level than in the conventional method, and the inclusions do not increase even at the seam. The origin of the inclusions was determined to be slag based on their composition.

[0013]

As described above, the method for separating molten metal and slag proposed in the present invention makes it possible to prevent the pan slag from flowing out to the tundish and to supply a clean molten metal to the solidification step. This method can be applied not only to the pan to the tundish but also to separate 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 view showing the relationship between the back pressure of the inert gas blowing and the level of the molten metal in this method.

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

FIG. 6 is a view showing the effect of improving the inclusion of seam cast slabs of the present method.

[Explanation of symbols]

1: Electromagnetic stirring coil 2: Refractory furnace wall with gas injection 3:
Inert gas 4: Molten metal floating bubble 5 Back pressure measuring device 6:
Inert gas blown slag centrifugal separator 7: Sliding nozzle 8: Pan 9: Long nozzle 10: Hot water level 11: Hot water bottom 12: Slag 13: Hot metal surface.

Claims (2)

[Claims] 1. From a container containing slag and molten metal,
In the method of separating the molten metal from the slag when moving the molten metal to another container, while injecting an inert gas into the molten metal from the wall surface while imparting a rotating motion perpendicular to the molten metal flow to the molten metal at the molten metal outflow portion of the container, A method for separating molten metal and slag, characterized in that air bubbles, inclusions, and slag are accumulated in the central portion by centrifugation, and the bubbles rise to separate and prevent slag from flowing out. 2. An inert gas is blown into the molten metal from the wall surface while rotating the liquid at a molten metal outflow portion of the container containing the slag and the molten metal in a direction perpendicular to the molten metal flow. In the method of separating molten metal and slag, in which objects and pot slag are accumulated in the center and floated / separated by rising bubbles, the amount of residual molten metal in the container is measured based on the change in back pressure of the blown inert gas. Then, a method for separating molten metal and slag is characterized by preventing the outflow of the slag by operating the sliding nozzle opening and the stopper opening.