JPH035067A - Apparatus for preventing flowing-out of slag in ladle and controlling method thereof - Google Patents

Abstract

PURPOSE:To prevent flowing-out of slag from a ladle by setting bar-like body, which has sp. gr. larger than that of molten steel and is possible to engage with upper part of molten steel discharging hole, ascending/descending the bar-like body and enabling measurement of the position in perpendicular direc tion and hanging force. CONSTITUTION:Molten steel flow rate from the molten steel discharging hole 12 at the bottom part of the ladle 10 is adjusted with the flowing rate adjusting means 14. Length of the bar-like body 18 is made to more than the molten steel depth developing vortex flow in the molten steel 16 and shape is made to engage with the upper part of the molten steel discharging hole 12 and the sp. gr. in made to larger than that of the molten steel. The bar-like body 18 is ascended/descended with ascending/descending means 20. Further, position of the bar-like body 18 in the perpendicular direction is measured with a position measuring means 22. Then, the hanging force of the bar-like body 18 is mea sured with a hanging force measuring means 24. By this method, the yield of steel can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for preventing slag from flowing out in a ladle to prevent slag from flowing out together with molten steel when molten steel is taken out from below a ladle filled with molten steel. It relates to a device and its control method.

As is well known, in the steelmaking process, the refined molten steel in the ladle is poured into the continuous casting tundish by opening a sliding nozzle from the tapping hole provided at the bottom of the ladle, and from the tundish into the mold. Slabs are produced by injection. In the process of pouring molten steel from the ladle mentioned above, what is important in producing clean steel is to prevent the slag floating on top of the molten steel in the ladle from flowing out. This is where a great deal of effort is being made.

The outflow of slag during pouring of molten steel from the ladle to the kunditshu is caused by (1) entrainment of the floating slag layer in the vortex generated directly above the ladle tap hole as the molten steel level in the ladle decreases;
and (2) outflow of the floating slag layer due to a delay in determining the end of ladle injection. Therefore, (1) above,
As a method for preventing slag outflow due to (2), a method for preventing slag outflow has already been proposed in Japanese Patent Laid-Open No. 60-210352.

This method is called the floating valve method, and when the molten steel level in the ladle drops and a vortex is generated, the floating valve is tightly arranged on the top.
The floating valve is placed at the slag-molten steel interface directly above the tap hole to prevent the generation of vortices and slag entrainment, and at the end of injection, the floating valve lands on the tap hole to block the tap hole and prevent floating slag from flowing out. This is what we are trying to do.

According to this technology, the generation of vortices can be effectively prevented and the entrainment of slag can be effectively prevented.
(3) (4) The effect of preventing slag outflow at the end of injection is not sufficient. In other words, if the refractories near the ladle tap hole and the refractories constituting the floating valve are eroded and their shapes change, the tap hole cannot be reliably blocked and slag will flow out at the end of pouring. There are often cases where

To solve this problem, JP-A No. 62-203667 discloses a method in which a float is placed at the interface between the slag layer and molten steel and lowered to follow the drop in the molten metal level to a predetermined height. A method is disclosed in which the descent is stopped at a certain point in time, the subsequent change in the buoyancy of the float is detected as a change in the tension of the float, and the tapping hole of the ladle is closed based on the change in the float's tension.

[Problem to be solved by the invention]

In this method, the timing of closing the tapping hole is determined based solely on changes in the tension applied to the float held at a predetermined height. Therefore, when the refractory near the tap hole changes its shape due to melting damage, the positional relationship between the top of the tap hole and the detection location changes, changing the state of the flow of molten steel and causing a timing shift. In addition, the state of the flow of molten steel changes depending on the state of thermal convection of the molten steel or the opening degree of the tapping hole, causing variations in the measured tension values, making it difficult to judge the sudden change, and as a result, the time of blockage can be determined. Sometimes I make mistakes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to propose a slag outflow prevention device and a control method thereof that improve the above-mentioned points.

[Means to solve the problem]

The slag outflow prevention device in a ladle according to the present invention is a device for preventing slag from flowing out of a ladle, which has a tapping hole at the bottom and has an outflow amount adjusting means for adjusting the amount of molten steel flowing out from the tapping hole. A rod-shaped rod having a length in the vertical direction equal to or higher than the molten steel level at which a vortex is generated in the molten steel, a bottom portion having a shape that engages with the upper part of the tapping hole, and a specific gravity that is greater than the specific gravity of the molten steel. The present invention includes an object, a lifting means for raising and lowering the rod-like object, a position measuring means for measuring the vertical position of the rod-like object, and a fishing force measuring means for measuring the fishing force of the rod-like object. This is a characteristic feature.

In addition, the method according to the present invention is a method for controlling the above-mentioned device, and includes the following steps: l) When the rod-shaped object is held above the molten metal surface and the rod-shaped object is preheated and plunges into molten steel, slag, molten steel, etc. 11) After the molten metal level has fallen to a height sufficient to prevent the adhesion of molten steel, the rod-shaped object is lowered and held above the molten metal surface, and After a sufficient period of time has elapsed, 111) the hot water level has decreased to about the length of the rod-shaped object in the vertical direction, the rod-shaped object begins to descend, and iv) the hanging force of the rod-shaped object has increased. After the weight becomes less than the value obtained by subtracting the buoyancy of the molten steel from the weight, it is assumed that the rod-shaped object has reached the upper part of the tapping hole, and the descent is stopped and the object is raised to a predetermined height and held; vi) when the rod-shaped object reaches the upper part of the tap hole, the outflow rate adjusting means closes the tap hole; It is characterized by:

[For production]

In step iv), the position of the rod-shaped object when it reaches the upper part of the outlet is known, and by rising from that position to a predetermined height, the position of the rod-shaped object and the upper part of the outlet are determined in order to obtain the timing to block the tap hole. The positional relationship between the two is always kept constant regardless of the state of erosion.

In addition, the timing of closing the slip ink nozzle is determined by changes in the suspension force, but if bare metal or slag adheres to the rod-shaped object, it will cause disturbance and be affected, so in step 11) the molten steel is preheated. It is designed to prevent adhesion when entering the area. Further, even if deposits adhere to the rod-shaped object due to insufficient preheating, the deposits can be sufficiently melted and removed by this preheating.

In order to detect the situation of melting loss, the rod-shaped object according to the present invention is composed of a metal that is sufficiently heavier than molten steel and a refractory covering it (7) (8), and its total specific gravity is higher than that of molten steel. is also set to large. Therefore, the rod-shaped object does not float near the surface of the molten steel.

Moreover, its length is designed to be longer than the level at which vortices are generated, and when the molten metal level falls below that length, it is submerged into the molten steel in step 111), so a part of it is always above the molten steel surface. This prevents the generation of vortices.

In order to reduce the cost of the rod-shaped object, the length of the rod-shaped object is shortened, and near the level where vortices occur, it is floated in the molten steel to prevent the eddy current, and when the rod-shaped object becomes less than the length of the rod, the vortex is prevented. 111) The same effect can also be obtained by performing the following operations.

In step (2), the rod-shaped object is lowered in synchronization with the descending speed of the molten metal surface, and after reaching the upper part of the tap hole, the tap hole is closed by the outflow rate adjusting means to maximize the molten steel without causing slag to flow out. It can be used for a limited time. In order to more reliably prevent the slag from flowing out, the descending speed of the rod-shaped object may be made faster than the descending speed of the molten metal surface. In this case, a small amount of molten steel remains, but it is not at a level that poses a problem.

〔Example〕

FIG. 1 is a diagram showing a device for preventing slag outflow in a ladle according to the present invention. A sliding nozzle 14 is provided in the middle of a long nozzle 12 provided at the bottom of the ladle 10,
The amount of outflow of molten steel 16 in ladle 10 is adjusted. 17 represents a slag layer. A rod-shaped object 18 suspended above the long nozzle 12 by a wire 28 is raised and lowered by a winch 32 that rotates as the motor U rotates, thereby moving up and down above the long nozzle 12.

A load cell 24 is provided in the middle of the wire 28, and the tension of the wire 28 is measured. The pulse generator 22 generates pulses in response to the rotation of the winch 32, and by counting these pulses, the vertical position of the rod-shaped object 18 is measured. Pulses from the pulse generator 22 and signals from the load cell 24 are input to a sequencer 30,
Sequence (9) (10) The morph 20 and the sliding nozzle 14 are controlled according to the signal from the sensor 30. 26 also represents a pot lid.

During preheating, the rod-shaped object 18 is set at a position between the pot lid 26 and the slag layer 17, and is naturally preheated by the ambient air temperature inside the pot.

Note that, in order to prevent damage due to overheating, it is preferable to provide piping for passing a cooling medium around the load cell 24 and the wire 28.

Further, a function for adjusting the positions of the long nozzle 12 and the rod-shaped object 18 may be provided above the wire 28, but it is not necessary since the ladle IU is normally set at approximately a predetermined position.

FIG. 2 is a diagram for explaining a method of controlling the apparatus shown in FIG. 1. Further, FIG. 3 is a flowchart of control of the sequencer 30. An example of the control method according to the present invention will be described with reference to FIG. 1, as well as FIGS. 2 and 3.

When the ladle 10 containing the molten steel 16 is installed at a predetermined position, the sliding nozzle (SN) 14 is opened to start taking out the molten steel, and the arm 34 is rotated so that the refractory stopper 18 closes the nozzle. It is located above 12. After waiting for a predetermined period of time until the hot water level drops to the level shown in column (a) of Fig. 2 (step a in Fig. 3), the stopper 18 is lowered to the preheating position shown in column (a) of Fig. 2. (step b). When the hot water level drops to a predetermined value, for example 700 mm (step C), the hot water level is lowered at a speed sufficiently faster than the falling speed of the hot water level (step d), and the value indicated by the load cell 24 is When the weight of the stopper is lower than the value obtained by subtracting the buoyancy of the molten steel (step e)
) When the upper part of the nozzle 12 is reached, the descending is stopped (see column (b) in FIG. 2, step f) in FIG. 3), and the vertical position at this time is set as the zero point of the position. Incidentally, the level at which vortices occur in molten steel is generally considered to be about 500 mm, and the above-mentioned 700 mm is a sufficiently higher level than this.

Next, it is raised 30 to 100 mm from the zero point and held (column (C) in FIG. 2, step g in FIG. 3). The lower the rising stroke at this time is, the better, as long as it does not interfere with the pouring speed from the ladle. Assuming that the interface between the slag and molten steel has reached near the lower end of the stopper 18 (FIG. 2 (d) column), the stopper 18 is then lowered at a speed that is equal to or faster than the lowering speed of the molten metal level. (Figure 2 (e) column, Figure 3 step J). When the stopper 18 reaches near the zero point in the vertical direction (
step k), the sliding nozzle 14 is closed;
The removal of the molten steel is completed (FIG. 2 (f) column, FIG. 3 step 1).

FIG. 4 shows actual measured values of the load cell value W when the operations (a) to (d) in FIG. z are performed. The period indicated by 8 is the preheating state shown in column (a) of FIG. The period indicated by B is the period during the descent from column (a) to column (b) in FIG. 2, and when reaching the upper part of the nozzle, W rapidly decreases.

The period indicated by C is the rising period from the column (b) in FIG. 2 to the position indicated in column (C). Thereafter, as the hot water level decreases, the buoyancy decreases and W gradually increases. W suddenly changes at the point indicated by D, which corresponds to the state shown in column (1) of FIG. 2. E indicates the timing at which the sliding nozzle started to close.

FIG. 5 is an enlarged view of the area near E in FIG. 4. As shown in the figure, the sliding nozzle is normally closed after this sudden change. Therefore, when a sudden change is confirmed, the rod-shaped object is lowered, and after reaching the upper part of the tapping hole, the sliding nozzle is closed, thereby preventing the slag from flowing out.

Effects of the Invention As described above, according to the present invention, it is possible to prevent the generation of vortices and the outflow of slag, and
By accurately grasping the timing of slag outflow, the yield can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining control for preventing slag outflow, Fig. 3 is a flowchart of the process, (13) (14) Fig. 4 is A diagram showing the change in load cell value W over time in the apparatus and method of the present invention. FIG. 5 is an enlarged view of a part of FIG. 4. In the figure, 10...Ladle, I2...Long nozzle,
14... Sliding nozzle 16... Molten steel, 17... Slag, 18.
...Stopper, 22...Pulse generator, 24...
・Load cell.

Claims (1)

[Claims] 1. Slag from a ladle (10) having a tapping hole (12) at the bottom and an outflow amount adjusting means (14) for adjusting the amount of molten steel flowing out from the tapping hole (12). A device for preventing outflow, having a length in the vertical direction equal to or higher than the molten steel level at which a vortex is generated in the molten steel (16), and having a shape at the bottom that engages with the upper part of the tapping hole (12). , a rod-shaped object (18) having a specific gravity greater than the specific gravity of molten steel, a lifting means (20) for raising and lowering the rod-shaped object (18), and a position for measuring the vertical position of the rod-shaped object (18). A device for preventing slag outflow in a ladle, comprising a measuring means (22) and a supporting force measuring means (24) for measuring the supporting force of the rod-shaped object (18). 2. A method for controlling the apparatus according to claim 1, comprising: i) when the rod-shaped object (18) is held above the molten metal surface and the rod-shaped object (18) is preheated and plunges into the molten steel, slag is generated; , after the molten metal level has fallen to a sufficient height to prevent the adhesion of molten steel, the rod-shaped object (18) is lowered and held above the molten metal surface, and ii) when it plunges into the molten steel, it prevents the adhesion of slag and molten steel. iii) after the hot water level has decreased to about the vertical length of the rod-shaped object, the rod-shaped object begins to descend, and iv) the suspension force of the rod-shaped object is reduced. becomes less than the value obtained by subtracting the buoyancy of the molten steel from the weight of the rod-shaped object (18), the rod-shaped object (18) is assumed to have reached the upper part of the tapping hole (12), and stops descending to a predetermined height. v) When the weight of the rod-shaped object (18) suddenly changes, the rod-shaped object (18) is lowered at a speed equal to or higher than the rate of descent of the hot water level, vi) the rod-shaped object (18) ) reaches the upper part of the tap hole (12), the outflow amount adjusting means (14) lowers the tap hole (12).
A method for controlling a device for preventing slag outflow in a ladle, the method comprising: blocking a slag outflow prevention device in a ladle.