JPS6021172A - Method for controlling cooling body of continuous casting device - Google Patents

Abstract

PURPOSE:To apply effective slight oscillation to a cooling body by maintaining only the reference position by position servocontrol and subjecting the displacement component by the slight oscillation to amplitude constant control without constituting the position servocontrol. CONSTITUTION:The lower frequency component below the high frequency component of slight oscillation among the displacement signals of a cooling body for a molten steel detected with a position detector 20 is selected with a low-pass filter 28 and is detected as a position feedback signal Sf0 for position servocontrol. The reference position of the cooling body is controlled by the position servocontrol loop I from a calculator 17 for a position deviation up to the filter 28 until said position is made equal to the set value S0 of a reference position setting device 15. On the other hand, the high frequency AC component of the slight oscillation is selectively detected with a band-pass filter 27 and the signal output thereof is converted by a full wave rectifier 26 to a DC signal from which an amplitude signal Af is obtd. The signal Af is then automatically controlled by the amplitude constant control loop II such as a calculator 29 for an amplitude deviation, etc. so that said signal is made equal to the set value A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to micro-vibration control of a cooling body in a continuous casting apparatus.

[Background of the invention]

In continuous casting equipment, in order to improve the surface quality of the slab and stabilize the solidification of molten steel, a method is used in which a high-cycle microvibration is applied to the cooling body in the direction in which the slab is pulled out.

FIG. 1 shows a conventional fine imaging control method. The molten steel 2 supplied from the nozzle 1 is cooled and solidified by the cooling body 5, becomes a slab 3, and is drawn out by the pinch rolls 12. Note that the cooling body 5 is cooled by a water stream (not shown). On the other hand, the cooling body 5 including the heat insulating body 4 can be displaced upwardly and downwardly by hydraulic operation with the external frame 6 side as a fixed side and the hydraulic lock 8 as a boundary. Hydraulic operation is performed by an electric signal using an electro-hydraulic servo valve 11, and the amount of displacement of the cooling body 5 is detected by a position detector 20 and fed back to the electric circuit side. The reference position So of the cooling body 5 is set by the reference position setting device 15. When not controlled, the cooling body 5 is placed on the stopper 22, but at the reference position S. is used to set the gap between the cooling body 5 and the stopper 22, and is set to a value greater than the slight vibration displacement so that the cooling body 5 does not hit the stopper 22 during minute vibrations. On the other hand, the micro-vibration displacement amount ΔS is set by the amplitude setter 14, and its frequency is set by the dial of the frequency generator 13. The reference position So and the slight vibration displacement amount ΔS are added by a command adder 16, and this added value is outputted as a position command S to a position deviation calculator 17. The position deviation calculator 17 calculates the deviation amount and direction of the detected current position value St with respect to the position command S, and generates a position deviation signal Δs.
, f: Output. The position error signal ΔS is amplified by the gain setting amplifier 18, and the current servo valve 11 is operated via the current amplifier 19. The gain setting amplifier 18 has a variable gain so that an appropriate safe position control gain can be set. The displacement of the cooling body 5 is controlled by the aforementioned position servo control so that it becomes equal to the position command S.

In FIG. 2, a solid line A indicates the frequency gain characteristic of the electro-hydraulic servo valve 11 alone. A broken line B shows the frequency gain characteristic of the actual displacement (position servo control) of the cooling body 5 with respect to the position command S when the Ω electro-hydraulic servo valve 11 is used.

As is clear from FIG. 2, the current servo valve 11 has approximately 200
Although it is attenuated compared to H2, the position servo control using this performs position feedback control, so it is about 1/6 of this.
It attenuates rapidly from near 30H2.

In order to effectively achieve the purpose of the micro-vibration of the cooling body 5,
A vibration frequency of 0-100H2 is required. In this practical frequency band 50 to 100H2, the actual displacement of the cooling body 5 is small even if the maximum permissible micro-vibration displacement amount ΔS is added to the command adder 16. Furthermore, in the conventional method, the broken line in FIG. As shown in B, the amplitude begins to decay at 30
The change in vibration S from around H2 to 100H2 is 80d13 or more (if it is too large, excessive vibration will be given to the slab, the solidified surface will be ruptured and breakout will occur, and the operation will be significantly hindered. If it is too high, sufficient vibration will not be applied to the cooling body 5, and the purpose of the micro-vibration will not be achieved.

In the conventional method, whenever the frequency is changed, the amplitude must be manually measured and readjusted, and if only the frequency is changed and the amplitude is forgotten, It has the disadvantage of falling into the dangers mentioned above. Conventional micro-vibration control has the disadvantage that sufficient vibration cannot be applied to the cooling body 5.

[Purpose of the invention]

An object of the present invention is to provide an entire micro-vibration control method that can apply effective micro-vibrations to a cooling body.

[Summary of the invention]

The object of the present invention is to achieve the object by a method in which only the reference position is held by position servo control, and minute vibration displacement is controlled to have a constant amplitude without position servo control.

[Embodiments of the invention]

FIG. 3 shows an embodiment of the present invention. Among the displacement signals of the cooling body 5 detected by the position detector 20, low frequency components below the microvibration high frequency component are selected by the low pass filter 28 and detected as the position feedback signal StO for position servo control. Reference position of cooling body 5 (1t
are a position deviation calculator 17, a gain setting amplifier 18, a current amplifier 19, an electro-hydraulic servo valve 11, a position detector 20. The set value S of the reference position setter 15 is controlled by the position servo control loop (dotted chain line I) constituted by the low-pass filter 28.
The position is controlled to be equal to O.

On the other hand, among the displacement signals of the cooling body 5 detected by the position detector 20, the minute vibration @ high frequency AC component is selectively detected by the bandpass filter 27.
The micro-vibration high-frequency AC signal output is converted into a DC signal by the full-wave rectifier 26, and an amplitude signal At of the micro-vibration high-frequency signal is obtained. The amplitude deviation calculator 29 calculates an amplitude deviation signal ΔA (ΔA = A − A
t) is calculated and output. The amplitude deviation signal ΔA is sent to the integrator 25
This integrated value is output to the multiplier 24 as the amplitude control signal (ii).The output signal a-sinωt of the frequency generator 13 is multiplied by the amplitude control signal by the multiplier 24, and its amplitude value a is automatically adjusted by the amplitude control signal K. In other words, the value of the amplitude control signal continues to change until the amplitude signal At of the actual micro-vibration high frequency becomes equal to the set value A, and the amplitude signal Af becomes equal to the set value A. is automatically controlled so that it is equal to
indicates time.

In this way, for the micro-vibration high-frequency component, a method is adopted in which the loop indicated by the chain double-dashed line (■) and constant amplitude control are configured. In addition, in FIG. 5, 71-i is a support frame, 9 is an oil supply hydraulic pipe, 10 is a return oil pressure pipe, 11 is an electro-hydraulic servo valve, 21 is a pressure oil, and 23 is an adder.

〔Effect of the invention〕

According to the present invention, sufficient and stable micro-vibration can be applied to the cooling body, thereby making it possible to improve the surface quality of the slab and the stability of solidification of molten steel.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a conventional control method, and FIG. 3 is an explanatory diagram of a control method according to the present invention.

Claims (1)

[Claims] 1. The reference position of the cooling body is continuous, characterized in that the actual position is maintained at the commanded position by a position control loop, and the high-frequency micro-vibration displacement of the cooling body is maintained at the commanded amplitude by constant amplitude control. A method for controlling the cooling body of a casting machine.