JPH02211957A - Device for controlling molten metal level in mold for continuous casting machine - Google Patents

Abstract

PURPOSE:To enhance control gain and to restrain oscillating phenomenon in control system even in the case of using high sensitive level by averaging control output values for controlling the level with oscillation cycle to make this average value the nozzle opening set value. CONSTITUTION:A mold level instrument S1 of vortex flow level instrument, etc., for detecting the molten metal surface level in the mold 3 is set at upper part of the mold 3, and further on the mold 3, a stroke detector S2 for detecting the oscillation stroke thereof and on a pinch roll 6 drawing down a continuous cast material 4, a revolution counter S3 are arranged. After amplifying the detected output of the mold level instrument S1 with an amplifier 11, PID arithmetic processing is executed and this is outputted to a control output value averaging arithmetic unit 13 as the control output value. The detected outputs of the oscillation stroke detector S2 and the revolution counter S3 for the mold 3 are fetched to an oscillation cycle arithmetic unit 14 to calculate the oscillation cycle, and this is outputted to the control output value averaging arithmetic unit 13. This device B calculates the nozzle opening degree set value based on the inputted control output value and the oscillation cycle and this is outputted to hydraulic servo system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scene level control device in a mold in a continuous casting machine.

[Conventional technology]

Level control of the molten steel scene inside the mold in a continuous casting machine is based on the level of the molten steel inside the mold detected by a mold level meter placed above the mold, and a PID controller performs PID calculation to determine the control output value. is determined and output to the hydraulic servo system for opening and closing the nozzle of the tundish, adjusting the nozzle opening and maintaining the scene level in the mold at the target value.

[Problem to be solved by the invention]

By the way, in such conventional control systems, for example, a highly sensitive eddy current level meter is used as a mold level meter,
Alternatively, when the control gain of the controller is increased, mold oscillation becomes noise in the output of the mold level meter, so-called oscillation noise, causing an oscillation phenomenon in the control system, and conversely there is a problem that control accuracy deteriorates.

The present invention has been made in view of the above circumstances, and its purpose is to provide a mold level control device that can control the noise of the mold level meter output and prevent the oscillation phenomenon of the control system. There is something to do.

[Means to solve the problem]

The mold level control device according to the present invention includes a mold level needle that detects the mold level and a control output value of the nozzle opening required to maintain the level constant based on the mold level needle output. The method includes means for calculating, means for determining an oscillation period based on the casting speed and mold oscillation, and means for averaging the control output value over the oscillation period and calculating a nozzle opening setting value.

[Effect]

The present invention can thereby increase the control gain and suppress the oscillation phenomenon of the control system even if a highly sensitive mold level meter is used.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 shows an in-mold hot water level control device according to the present invention (
1 is a schematic diagram of the apparatus (hereinafter referred to as the apparatus of the present invention), in which 1 is a ladle, 2 is a tundish, 3 is a mold, and 4 is a continuous casting material.

Molten steel flows from a ladle l through a nozzle 1a to a tundish 2, and from this tundish 2, it is supplied into a mold 3 through a gate 2a whose opening is set by a hydraulic cylinder 5, and a nozzle 2b.

The molten steel supplied into the mold 3 is gradually cooled and solidified, and is pulled down to the bottom of the mold 3 by the oscillation of the mold 3 and the pinch rolls 6, etc., and is cast into a continuous casting material 4. becomes.

A mold level meter 31 such as an eddy current level meter for detecting the scene level inside the mold 3 is arranged above the mold 3, and a stroke detector St for detecting the oscillation stroke of the continuous casting material is further installed in the mold 3. The pinch rolls 6 for pulling down the rollers 4 are each provided with a tachometer S.

The detection output of the mold level meter 81 is amplified by the amplifier 11, then subjected to PID calculation by the PID calculation device 12, and outputted to the control output value averaging calculation device 13 as a control output value.

The detection output of the oscillation stroke detector S2 of the mold 3 and the detection output of the tachometer S are respectively taken into the oscillation period calculation device 14, and the oscillation period is calculated according to the following formula (11), and this is calculated as the control output value average. output to the conversion calculation unit 13.

X5TR However, vc: Casting speed (m/min) STR: Oscillation stroke (Tsuru) NS: Negative strip rate (%) The control output value averaging calculation device 13 calculates the input control output value and oscillation period. Based on this, a nozzle opening setting value is calculated according to the following equation (2), and this is output to the hydraulic servo system 15.

However, the important point is...nozzle opening setting value MV...control output value N"Tosc/ΔT (ΔT: control period (seconds))Next, a comparative test was conducted using the device of the present invention and the conventional device. The results will be explained.The conditions of the continuous casting machine used in the test are as follows.

Mold size: Vertical...2350111 Horizontal = b Casting speed 20.2~lb/sec Oscillation stroke = 4 drunkenness Negative strip rate 835% The results are shown in FIGS. 2 and 3.

Figure 2 shows the results when using the device of the present invention, and Figure 3 (a)
, (b) show the level of the hot water in each mold when using the conventional device, and in both cases, the horizontal axis represents time (seconds), and the vertical axis represents the hot water level in the mold.

As is clear from this graph, in the case of the device of the present invention, by setting the control gain appropriately, the level fluctuation in the mold (±2 m) is greatly improved, and high control accuracy is obtained. On the other hand, in the conventional device shown in Fig. 3, when the control gain is low, no oscillation phenomenon due to mold oscillation is observed as shown in Fig. 3 (a), but there is a level fluctuation at low frequency (30 seconds). (±7 fins) occurs, and when the control gain is increased, as shown in Figure 3 (b), there is no low frequency level fluctuation, but high frequency level fluctuations due to oscillation noise (±5 fins). It can be seen that this is occurring.

Table 1 shows the percentage (%) of level fluctuations of ±2M or less and the incidence of slipper teams (%) for the device of the present invention and the conventional device.
It shows.

Table 1 As is clear from Table 1, the amount of level fluctuation was significantly reduced,
It can also be seen that the occurrence of slipper flaws is significantly reduced.

〔effect〕

As described above, in the device of the present invention, the control output value for level adjustment is averaged in the oscillation period and used as the nozzle opening setting value, so the control gain is increased and the high-sensitivity mold level meter is used. The present invention has excellent effects, such as being able to effectively suppress oscillation noise caused by mold oscillation and preventing oscillation of the control system even when using a control system, resulting in high control accuracy. .

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the device of the present invention, Fig. 2 is a mold level waveform diagram when using the device of the present invention, and Figs. 3 (a) and (b) are mold level waveform diagrams when using the conventional device. It is. ■...Dollar 2...Tandaitsu 3...
Mold 4... Continuous casting material 5... Hydraulic cylinder 6... Pinch roll 11... Output amplifier of eddy current level meter 12... PID computing device 13... Control output value averaging computing device 14. ...Oscillation period calculation device straw 2 Figure 30 Seconds Funeral Diagram

Claims (1)

[Claims] 1. A mold level meter for detecting the level of molten metal in the mold, a means for calculating a control output value for the nozzle opening degree necessary to maintain the level constant based on the output of the mold level meter, and a means for calculating the control output value for the nozzle opening degree necessary to maintain the level constant; Molten surface in a mold of a continuous casting machine characterized by comprising means for determining an oscillation period based on oscillation, and means for averaging the control output value over the oscillation period and calculating a nozzle opening setting value. Level control device.