JPH0642987B2 - Apparatus and method for preventing outflow of slag in ladle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus and a method for preventing slag from flowing out together with molten steel when the molten steel is taken out from below a ladle filled with molten steel.

[Conventional technology]

As is well known, in the steelmaking process, molten steel in a refined ladle is poured into a tundish of continuous casting by opening a sliding nozzle from a tap hole provided at the bottom of the ladle,
Cast pieces are manufactured by pouring from a tundish into a mold. In the process of injecting molten steel from the ladle described above, what is important in producing clean steel is to prevent the slag floating on the molten steel in the ladle from flowing out. This is where a great deal of effort is being put into.

The outflow of slag when pouring molten steel from the ladle into the tundish is as follows: (1) Entrainment of the levitation slag layer in the vortex flow generated immediately above the ladle tap hole as the molten steel level in the ladle decreases, and ( 2) It can be roughly divided into the outflow of the floating slag layer due to the delay in determining the end of ladle injection. Thus, as a method for preventing the outflow of slag according to the above (1) and (2), it has already been disclosed in JP-A-60-210352
A slag outflow prevention method has been proposed in Japanese Patent Publication.

This method is called a floating valve system, and when the molten steel level in the ladle of which the specific gravity is adjusted decreases and a swirl occurs, the slag-molten steel interface directly above the tap hole It is intended to prevent the outflow of the floating slag by preventing the generation of a vortex and preventing the entrainment of the slag, and landing the floating valve on the tap hole at the end of pouring to close the tap hole.

According to this technique, it is possible to effectively prevent the generation of the vortex flow and effectively prevent the slag from being entrained, but the effect of preventing the slag outflow at the time of the completion of the injection is not sufficient. That is, when the refractory near the ladle tap hole and the refractory forming the floating valve are melted and changed in shape, the tap hole cannot be reliably blocked and the slag flows out at the end of pouring. It often happens.

Japanese Patent Laid-Open No. 62-203667 discloses a solution to this problem in which the float is positioned at the interface between the slag layer and the molten steel, and is lowered to follow the molten metal level drop to a predetermined height. A method is disclosed in which the descent is stopped at a point of time, a change in the buoyancy of the float thereafter is detected by a change in the tension of the float, and the tap hole of the ladle is closed based on the detection.

[Problems to be Solved by the Invention] In this method, the timing of closing the tap hole is obtained only based on the change in the tension applied to the float held at a predetermined height. Therefore, when the refractory material near the tap hole melts and the shape changes, the positional relationship between the upper part of the tap hole and the detection point changes, the flow state of the molten steel changes, and timing deviation may occur. In addition, the state of molten steel flow changes depending on the state of thermal convection of molten steel or the opening of the tap hole, causing variations in the measured tension values, making it difficult to determine abrupt changes. I may make a mistake.

Therefore, it is an object of the present invention to propose a slag outflow prevention device and method that improve the above points.

[Means for Solving the Problems]

The device for preventing slag outflow in a ladle according to the present invention is a device for preventing outflow of slag from a ladle having a tap hole at the bottom and having an outflow amount adjusting means for adjusting the amount of molten steel outflow from the tap hole. And a rod-shaped object having a vertical length equal to or higher than the molten steel level at which eddy currents are generated in the molten steel and having a specific gravity greater than the specific gravity of the molten steel, an elevating means for moving the rod-shaped object up and down, and the rod-shaped object Position measuring means for measuring the vertical position of the rod-shaped object, fishing-force measuring means for measuring the fishing-force of the rod-shaped object, the elevating means, position-measuring means, and fishing-force measuring means, A means for holding the rod-like object at a position in which the bottom of the object is located above the position of the upper surface of the tap hole by a predetermined height and the fishing-force measuring means, and the fishing-force measured by the fishing-force measuring means. Detects an increase in supporting force at a speed higher than a predetermined speed And a means coupled to the detecting means and the outflow rate adjusting means, and means for closing the tap hole by the outflow rate adjusting means after the detecting means detects an increase at a speed equal to or higher than the predetermined speed. It is characterized by that.

Further, the method for preventing slag outflow in a ladle according to the present invention is for preventing the outflow of slag from a ladle having a tap hole at the bottom and having an outflow amount adjusting means for adjusting the molten steel outflow amount from the tap hole. In the method, a rod-shaped object having a vertical length equal to or higher than the molten steel level at which eddy currents are generated in the molten steel and having a specific gravity that is greater than the specific gravity of the molten steel, in which the bottom is from the top surface position of the tap hole It is characterized in that the tap hole is closed by the outflow amount adjusting means after being held at a predetermined height above and the fishing force of the rod-shaped object increases at a speed equal to or higher than a predetermined speed. .

[Action]

The positional relationship between the position of the rod-shaped object and the upper portion of the outlet for obtaining the timing of closing the tap hole by rising to a predetermined height from the position when the rod-shaped object reaches the upper portion of the outlet is It is always kept constant regardless of.

In order to detect the state of melting loss, the rod-shaped object in the present invention is composed of a metal sufficiently heavier than molten steel and a refractory covering it, and the total specific gravity is set to be larger than that of molten steel. . 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 eddy currents occur, and when the level of the molten metal falls below that length, part of it always comes out of the molten steel surface, preventing eddy currents from occurring. .

In order to reduce the cost of the rod-shaped object, the length of the rod-shaped object is shortened, and the vortex is prevented by floating it in the molten steel near the level where the vortex is generated. The same effect can be obtained by holding the above position.

After the fishing force of the rod-shaped object increases at a speed equal to or higher than a predetermined speed, the molten metal can be used to the maximum without flowing out the slag by closing the tap hole by the flow amount adjusting means. In order to prevent the slag from flowing out more reliably, the descending speed of the rod-shaped object may be set higher than the descending speed of the molten metal surface. In this case, a slight amount of molten steel remains, but this is not a problematic level.

〔Example〕

FIG. 1 is a view showing a slag outflow prevention device in a ladle according to the present invention. Long nozzle 12 at the bottom of ladle 10
A sliding nozzle 14 is installed on the way to the ladle 10.
The outflow amount of the molten steel 16 inside is adjusted. Reference numeral 17 represents a slag layer. The rod-like object 18 supported by the wire 28 above the long nozzle 12 is hoisted and unwound by a winch 32 that is rotated by the rotation of the motor 20, and moves 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 a pulse according to the rotation of the winch 32,
By counting this pulse, the vertical position of the rod-shaped object 18 is measured. The pulse from the pulse generator 22 and the signal from the load cell 24 are input to the sequencer 30, and the motor 20 and the sliding nozzle 14 are controlled according to the signal from the sequencer 30. In addition, 26 indicates a pot lid. At the time of preheating, the rod-shaped object 18 is set at a position between the pot lid 26 and the slag layer 17 and naturally preheated by the ambient temperature in the pot.

In addition, in order to prevent damage due to overheating, it is preferable to provide a pipe 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 the normal ladle 10
Does not need to be set because it is set at a substantially predetermined position.

FIG. 2 is a diagram for explaining a control method of the apparatus of FIG. 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 and 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 the extraction of the molten steel, and at the same time, the arm 34 is rotated and the refractory stopper 18 is opened. It is located above the nozzle 12. After waiting for a predetermined time and waiting for the level of the molten metal to decrease to the level shown in Fig. 2 (a), the stopper 18 descends to the preheat position shown in Fig. 2 (a). And held (step b). When the molten metal level falls to a predetermined value, for example 700 mm (step C), it is lowered at a speed sufficiently faster than the descending velocity of the molten metal level (step d), and the load cell
When the value indicated by 24 decreases below the value obtained by subtracting the buoyant force of molten steel from the weight of the stopper (step e), it is assumed that the nozzle 12 has been reached, and the descent is stopped (column in FIG. 2 (b), step f in FIG. ), And the vertical position at this time is the zero point of the position. In addition, the level of the melt surface at which eddy currents are generated in molten steel is generally
It is said to be about 500 mm, and the above-mentioned 700 mm is a level sufficiently higher than this. Next, it is raised by 30 to 100 mm with respect to the zero point and held (FIG. 2 (c) column, FIG. 3, step g). The ascending stroke at this time is preferably as low as possible so long as it does not hinder the pouring speed from the ladle. The value W from the load cell 24 is continuously monitored, and if there is a sudden change, it is assumed that the boundary surface between the slag and the molten steel has reached near the lower end of the stopper 18 (column (d) of FIG. 2), and then the melt level. Stopper 18 synchronized with the descending speed of
Is lowered (column (e) in FIG. 2, step j in FIG. 3).
When the stopper 18 reaches near the zero point in the vertical direction (step k), the sliding nozzle 14 is closed and the taking out of molten steel is completed (FIG. 2 (f) column, FIG. 3 step l). As described above, the sliding nozzle closing timing is performed by the change in the fishing support force, but if metal or slag adheres to the rod-shaped object, it will cause disturbance and will be affected, so the rod-shaped object will be immersed in molten steel. By pre-heating it before, it is possible to prevent it from adhering to the molten steel. Further, even if the deposit adheres to the rod-shaped object due to insufficient preheating, the preheating sufficiently melts and removes the deposit.

FIG. 4 shows the measured value of the value W of the load cell when the operations (a) to (d) of FIG. 2 are performed. The period indicated by A is the state during preheating shown in the column (a) of FIG. The period indicated by B is a period in which the column (a) in FIG. 2 is descending to the column (b), and when it reaches the upper portion of the nozzle, W sharply decreases.
The period indicated by C is a rising period from the column (b) to the position indicated by column (c) in FIG. After that, the buoyancy decreases as the molten metal level decreases, and W gradually increases. W changes abruptly at the point indicated by D, which corresponds to the state shown in the column (d) of FIG. E represents the timing at which closing of the sliding nozzle was started.

FIG. 5 is an enlarged view in the vicinity of E in FIG. As shown in the figure, normally, the sliding nozzle is closed after this sudden change. Therefore, the outflow of slag can be prevented by closing the sliding nozzle after the rod-shaped object descends and reaches the upper portion of the tap hole upon confirmation of a sudden change.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the generation of a vortex and prevent the outflow of slag,
By accurately grasping the timing of slag outflow, the effect of improving the yield can be obtained.

[Brief description 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 processing, and FIG. 4 is an apparatus and method of the present invention. FIG. 5 is a diagram showing the change over time of the load cell value W, and FIG. 5 is an enlarged view of a part of FIG. In the figure, 10 ... Ladle, 12 ... Long nozzle, 14 ... Sliding nozzle, 16 ... Molten steel, 17 ... Slag, 18 ... Stopper, 22 ... Pulse generator, 24 ... Load cell.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masato Masazawa, 1st Kimitsu, Kimitsu-shi, Chiba Shin-Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. (72) Hideyoshi Yoshimura, 1st Kimitsu, Chizu-Shi Kimitsu Steel Works, Ltd. (56) References JP 62-203667 (JP, A) JP 60-210352 (JP, A) JP 60-186963 (JP, U)

Claims (2)

[Claims] 1. A slag outflow from a ladle (10) having a tap hole (12) at the bottom and an outflow amount adjusting means (14) for adjusting the outflow amount of molten steel from the tap hole (12). A rod-shaped object (18) having a vertical length equal to or higher than the molten steel level at which eddy currents are generated in the molten steel (16) and having a specific gravity larger than the specific gravity of the molten steel; Lifting means (20) for moving the object (18) up and down, position measuring means (22) for measuring the vertical position of the rod-shaped object (18), and fishing for measuring the fishing support force of the rod-shaped object (18). Support force measuring means (24)
And the lifting means (20), the position measuring means (22), and the fishing support force measuring means (24) are combined, and the bottom of the rod-shaped object (18) is connected to the tap hole (1
A means for holding the rod-shaped object at a position above the upper surface position of 2) by a predetermined height and a means for measuring the supporting force of the fishing rod (24) are combined with the means for measuring the supporting force of the fishing rod (2).
4) means for detecting an increase in the fishing support force at a speed equal to or higher than a predetermined speed, and the detection means and the outflow amount adjusting means (14) are coupled, and the detection means is equal to or higher than the predetermined speed. And a means for closing the tap hole (12) by the outflow amount adjusting means (14) after detecting the increase in the speed of the ladle. 2. Preventing outflow of slag from a ladle (10) having a tap hole (12) at the bottom and an outflow amount adjusting means (14) for adjusting the outflow amount of molten steel from the tap hole (12). I) a rod-shaped object (18) having a vertical length equal to or higher than a molten steel level at which eddy currents are generated in the molten steel (16) and having a specific gravity larger than that of the molten steel, The bottom is held at a position above the upper surface of the tap hole (12) by a predetermined height, and ii) after the fishing force of the rod-like object (18) increases at a speed equal to or higher than a predetermined speed, Outflow hole (12) by means of outflow control (14)
A method for preventing outflow of slag in a ladle, which is characterized by blocking the inside.