JPH0639504A - Device for controlling plasma-heating for molten steel in tundish - Google Patents

Abstract

PURPOSE:To precisely control a molten steel temp. in a tundish in a prescribed range with simple constitution. CONSTITUTION:By detecting an arc voltage with a plasma torch, a distance between the relative position of the plasma torch, when the detected arc voltage corresponds to the setting arc voltage to the molten steel surface in the tundish 11 is used as the reference distance and a computing element 18 controls a motor 16 for ascending/descending following to the variation of the molten steel surface level obtd. based on the detected tundish wt. so that the distance between the molten steel surface and the plasma torch 12 becomes the reference distance. In such a manner, since the ascending/descending of the plasma torch 12 is controlled so as to keep the reference distance after obtaining the reference distance even if the length of the plasma torch caused by consumption, etc., is varied and the wt. of the tundish itself is varied by precisely controlling the distance between the molten steel surface and the plasma torch 12 to the prescribed distance, the molten steel temp. in the tundish 11 can precisely be kept in the prescribed temp. range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating control device for heating and controlling molten steel in a tundish with plasma in a continuous casting facility.

[0002]

2. Description of the Related Art In continuous casting equipment, molten steel stored in a ladle is supplied (poured) to a mold through a tundish, and the cast piece is continuously cast by pulling out the cast piece from the mold. is doing.

Generally, in order to obtain a slab of good quality, it is necessary to appropriately control the molten steel temperature when pouring the molten metal from the tundish into the mold. A device described in JP-A-3-124351 or JP-A-3-285746 is known (hereinafter, the plasma heating apparatus described in JP-A-3-124351 is referred to as a first plasma heating apparatus, and The plasma heating device described in JP-A-3-285746 is called a second plasma heating device).

In the first plasma heating apparatus, the current supplied to the plasma torch is detected, the arc voltage in the plasma torch is detected, and the electric power supplied to the plasma torch is made constant based on the detected current and the detected arc voltage. The temperature of molten steel in the tundish is controlled within a predetermined range.

On the other hand, in the second plasma heating apparatus, the height position of the plasma torch is detected with the top of the heating chamber as a reference plane, and the weight of molten steel including the weight of the tundish is measured by the load cell. Control the plasma torch up and down based on the position and measured weight,
The arc length by the plasma torch is adjusted. In this way, even if the molten steel level in the tundish varies, the arc length is controlled to be constant, and the molten steel temperature in the tundish is kept within a predetermined range.

[0006]

In the first plasma heating apparatus, it is necessary to detect the current supplied to the plasma torch and the arc voltage in the plasma torch. Based on these detection values, the plasma torch is supplied. Therefore, there is a problem in that the control of the power supply to the plasma torch becomes complicated and the control device itself becomes expensive.

In the second plasma heating apparatus, since the plasma torch faces the molten steel at high temperature, the plasma torch is melted and the length of the plasma torch itself changes during use. As described above, when the length of the plasma torch changes, a deviation occurs between the actual height position and the detected height position with respect to the reference surface. That is, it becomes impossible to accurately detect the actual height position of the plasma torch. Furthermore, since the refractory bricks that make up the tundish are constantly in contact with the high temperature molten steel, the tundish refractory bricks are also melted and the tundish's own weight changes. When the weight of the tundish changes,
Since the specific gravities of refractory bricks and molten steel are different, there is a difference between the actual molten steel level in the tundish and the molten steel level based on the measured tundish weight.
In other words, the molten steel level in the tundish cannot be accurately detected.

When the above-mentioned deviation (error) occurs, the second plasma heating device causes the plasma torch to move depending on the detected height position of the plasma torch with respect to the reference surface and the molten steel level in the tundish based on the measured weight of the tundish. Due to the control of the arc length, it is difficult to control the actual arc length to be constant, and it becomes impossible to maintain the molten steel temperature in the tundish within a predetermined range. On the other hand, even if it is attempted to correct the above error and control the arc length to be constant, it is extremely difficult to accurately grasp the change in the length of the plasma torch and the change in the weight of the tundish. It is difficult to control.

An object of the present invention is to provide a plasma heating control device capable of controlling the molten steel temperature in the tundish within a predetermined range with high precision without requiring complicated power control.

[0010]

According to the present invention, there is provided a plasma heating control device for plasma heating controlling molten steel in a tundish provided in a continuous casting facility, wherein a plasma arc is generated between the molten steel surface and the molten steel surface. Plasma torch,
Moving means for moving the plasma torch in a direction perpendicular to the molten steel surface, detecting means for detecting a moving amount by the moving means as a detected moving amount, and weight detecting means for detecting the weight of the tundish as a detected weight. And an arc voltage detecting means for detecting an arc voltage in the plasma torch as a detected arc voltage, and a relative position between the plasma torch relative to the molten steel surface when the detected arc voltage matches a preset arc voltage. With the distance as a reference distance, the moving means is controlled to follow the fluctuation of the molten steel surface level obtained based on the detected weight, and the distance between the molten steel surface and the plasma torch is controlled to be the reference distance. A molten steel plasma heating control device in a tundish is obtained.

[0011]

In the present invention, the distance between relative positions of the plasma torch with respect to the molten steel surface when the arc voltage by the plasma torch matches the set arc voltage is used as a reference distance,
After that, the plasma torch is driven (elevated) so as to maintain the reference distance according to the variation of the molten steel surface level grasped by the detected weight of the tundish. In this way, after the reference distance is obtained, the plasma torch is controlled to move up and down so as to maintain the reference distance.Therefore, the length of the plasma torch changes due to melting damage or the self-weight of the tundish itself. Even if it changes, the distance between the molten steel surface and the plasma torch can be accurately controlled to a predetermined distance,
As a result, the molten steel temperature in the tundish can be accurately maintained within a predetermined temperature range.

[0012]

EXAMPLES The present invention will be described below with reference to examples.

With reference to FIG. 1, a tundish 11 is provided in the continuous casting facility, and molten steel is supplied to the tundish 11 from a ladle (not shown) through a hot water supply nozzle 11a. It is temporarily stored in 11. The molten steel in the tundish 11 is the pouring nozzle 11b.
Is supplied to the mold (mold, not shown) via the.

The plasma heating controller is a plasma torch 1
The plasma torch 12 is inserted in the tundish 11. Then, a voltage is applied to the plasma torch 12 from a voltage applying device (not shown). The plasma torch 12 is supported by a plasma torch elevating device 13, and the plasma torch elevating device 13 is supported by the torch guide part 14 so as to be movable along the torch guide part 14. The torch guide portion 14 is supported by the mount 15. For example, a wire rope 13 a is connected to the plasma torch lifting device 13, and the lifting motor 16 is driven to drive the wire rope 1 a.
The plasma torch elevating / lowering device 13 moves up and down along the torch guide portion 14 by winding up or winding down 3a.

The tundish 11 is supported by a load cell 17, which is connected to a computing unit 18. An arc voltage detector 19 is connected to the plasma torch 12, and the arc voltage detector 19 is connected to a comparator 20. A voltage setter 21 is connected to the comparator 20, and the comparator 20 is connected to the calculator 18. A plasma torch position detector 22 is further connected to the calculator 18, and the calculator 18 drives and controls the lifting motor 16 as described later.

Here, the molten steel heating control in the tundish 11 will be described with reference to FIG.

First, the set arc voltage is set by the voltage setter 21. Then, an applied voltage is applied to the plasma torch 12 from the voltage applying device. The arc voltage changes according to the molten steel level in the tundish 11, that is, according to the distance between the plasma torch 12 and the molten steel surface, and the arc voltage by the plasma torch 12 is continuously detected by the arc voltage detector 19. Detected and comparator 2
Given to 0. Then, when the detected arc voltage matches the set arc voltage, the comparator 20 sends a match signal. Then, the calculator 18 starts drive control of the lifting motor in response to the coincidence signal. That is, the calculator 18 starts the plasma torch lift control when the detected arc voltage reaches the set value (in other words, the calculator 18 controls the lift of the plasma torch when the distance between the molten steel surface and the plasma torch becomes a predetermined interval. Start).

When the plasma torch elevation control is started, the calculator 18 continuously receives the weight measurement signal from the load cell 17. The relationship between the tundish molten steel surface level and (tundish weight + molten steel weight) is preset as a molten steel surface level curve for each tundish, and the type of tundish is given to the calculator 18 for heating control. As a result, the calculator 18 selects a specific molten steel surface level curve.

On the other hand, as described above, when the detected arc voltage and the set arc voltage match, the distance between the molten steel surface and the plasma torch is a desired distance, and the relative position between this molten steel surface and the plasma torch. The distance between them becomes the reference distance.

Tundish 1 from ladle not shown
When the molten steel surface level in the tundish 11 fluctuates due to hot water supply to 1 or pouring from the tundish 11 into a mold (not shown), (tundish weight + molten steel weight) changes, and the calculator 18 uses this signal from the weight measurement signal. Knowing the change, the molten steel surface level in the tundish 11 is obtained from the molten steel surface level curve. As a result, for example, when the molten steel surface level decreases and the distance between the molten steel surface and the plasma torch becomes larger than the reference distance, the calculator 18 causes the lifting motor 1 to move.
6 is driven and controlled, and the plasma torch lifting device 13 is lowered along the torch guide portion 14. At this time, the driving amount of the lifting motor 16 is, that is, the plasma torch lifting device 1
The moving amount of 3 is detected by the plasma torch position detector 22 and given to the calculator 18 as a position signal. Then, the calculator 18 uses the position signal to detect the plasma torch 1
When the position 2 (the amount of movement from the lifting control start position) is known and the distance between the molten steel surface level and the plasma torch 12 becomes the reference distance, the lifting motor 16 is stopped.

Similarly, when the molten steel surface level rises and the distance between the molten steel surface and the plasma torch becomes smaller than the reference distance, the calculator 18 drives and controls the lifting motor 16 to move along the torch guide portion 14. Plasma torch lifting device 13
Raise. Then, the arithmetic unit 18 knows the position of the plasma torch 12 from the position signal, and when the distance between the molten steel surface level and the plasma torch 12 becomes the reference distance, the lifting motor 16 is stopped.

In the above embodiment, for example, even when the length of the plasma torch changes due to melting damage and the weight of the tundish itself changes, when the set arc voltage and the detected arc voltage match at the time of starting. Since the distance between the relative position of the plasma torch and the molten steel surface level of the tundish is used as the reference distance, the up and down control of the plasma torch is performed to maintain this reference distance. Can be absorbed. As a result, the arc voltage can be accurately maintained at the set arc voltage, and the molten steel in the tundish can be accurately heated and controlled within a predetermined temperature range.

The torch and tundish are replaced and repaired (hereinafter referred to as "replacement", etc.) as necessary. This replacement, etc., is a process from start to stop of the continuous casting equipment (hereinafter, this process is called "charge"). After a large number of times, the torch meltdown and the tundish's own weight change are negligibly small in one charge.

In the above-mentioned embodiment, the example of raising and lowering the plasma torch by winding or lowering the wire rope has been described, but not limited to such winding or lowering drive, a rack and pinion, a cylinder, a screw jack or the like is used. Alternatively, the plasma torch may be driven and controlled.

In a continuous casting facility, the tundish itself may be lifted and lowered while being supported by a load cell in order to adjust the molten steel surface level. In this case, the gantry is moved up and down in synchronization with or integrally with the tundish so that the relative positional relationship between the tundish and the plasma torch is not changed.

[0026]

As described above, in the present invention, the distance between the relative positions of the plasma torch with respect to the molten steel surface when the arc voltage by the plasma torch matches the set arc voltage is set as the reference distance, and this reference distance is obtained. After that, the plasma torch is controlled to move up and down to maintain the reference distance, so even if the length of the plasma torch changes due to melting damage, etc. The relative distance between the surface and the plasma torch can be controlled to match the reference distance, and as a result,
There is an effect that the molten steel temperature in the tundish can be accurately maintained within a predetermined temperature range.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a plasma heating control device according to the present invention.

[Explanation of symbols]

 11 Tundish 12 Plasma torch 13 Plasma torch lifting device 14 Torch guide part 15 Frame 16 Lifting motor 17 Load cell 18 Calculator 19 Arc voltage detector 20 Comparator 21 Voltage setting device 22 Plasma torch position detector

Claims (1)

[Claims] 1. A plasma heating control device for controlling plasma heating of molten steel in a tundish provided in a continuous casting facility, comprising: a plasma torch for generating a plasma arc between the molten steel surface and the molten steel surface. Moving means for moving the plasma torch in the vertical direction, and detecting means for detecting a moving amount by the moving means as a detected moving amount,
Weight detection means for detecting the weight of the tundish as the detected weight, arc voltage detection means for detecting the arc voltage in the plasma torch as the detected arc voltage, and the detected arc voltage matches the preset arc voltage. When the distance between the relative positions of the plasma torch with respect to the molten steel surface at the time is a reference distance, the moving means is controlled to follow the variation of the molten steel surface level obtained based on the detected weight and the molten steel surface and the A molten steel plasma heating control device in a tundish, comprising control means for controlling the distance to the plasma torch to be the reference distance.