JPS63183764A - Continuous casting machine mold abnormality monitoring method and device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for monitoring abnormalities in a mold of a continuous casting machine.

(Prior art and its problems) In general, surface defects such as vertical cracks that occur on the surface of a slab cast during continuous steel casting are greatly affected by the initial solidification state in the mold, especially between the mold and the slab. It is well known that there is a close relationship with the inflowing mold powder, and that defects occur when the inflow situation is uneven, and breakouts tend to occur at such times. A method has been proposed for detecting and monitoring the inflow of powder as the frictional force between the mold and the slab (Japanese Patent Laid-Open No. 57-68256, Japanese Patent Laid-Open No. 57-112962,
(Japanese Patent Application Laid-open No. 121057/1983).

However, these conventional methods have major problems. First, in the method of attaching strain gauges and accelerometers to the mold vibration generation mechanism and detecting the frictional force between the mold and the slab as changes in stress and disturbances in the mold vibration waveform, the mold vibration generation mechanism is generally highly rigid, Changes in the frictional force between the slabs do not appear in the measured values.

Therefore, highly sensitive strain gauges and accelerometers are used, but the continuous casting machine itself has high vibrations (for example, vibrations caused by the flow of mold cooling water), resulting in measurement with many disturbances, and in order to remove these disturbances, filters are used. When installed, the desired signal is also attenuated, resulting in unreliable measurements and is not practical.

Alternatively, a method using a load cell has been proposed, but as mentioned above, the difference between the frictional force in a normal state and the frictional force in an abnormal state cannot be detected by a load cell. Not practical.

Furthermore, there is another method to measure the thickness of the powder film by attaching an ultrasonic sensor, etc. to the back of the mold surface that comes into direct contact with the casting mold, and to measure the powder inflow situation. -1 Not practical due to maintainability.

This invention was proposed in view of these circumstances, and its purpose is to provide a continuous casting machine that can be put to practical use in terms of disturbance and detector maintainability, and that can perform highly reliable monitoring. An object of the present invention is to provide a mold abnormality monitoring method and device.

(Means and effects for solving the problem) The abnormality monitoring method of a continuous casting machine mold according to the present invention utilizes the fact that changes in the frictional force of the mold and slab appear as changes in slab speed. The casting speed is directly detected by the rotation of the single support roll, and when the change in the casting speed becomes larger than the set value, it is determined that there is an abnormality in the frictional force at the contact surface between the mold and the slab, and highly reliable monitoring is performed. It was made possible to do so.

Next, the abnormality monitoring device according to the present invention includes a speed detector connected to the slab support roll, which detects and outputs the casting speed, a speed command device which gives a speed command to the pinch roll group, and a speed detector connected to the slab support roll. It consists of a signal processing circuit that subtracts the detection signal from the speed command signal from the speed command device and outputs an abnormal signal when the subtracted value becomes larger than the set value. This system does not require a processing circuit and can perform highly reliable monitoring with a relatively simple configuration.

(Embodiment) The present invention will be described below based on an illustrative embodiment.

As shown in FIG. 1, the mold 1 is driven by an eccentric cam 3. The cast slab 5 is vibrated through the vibrating table 2 and is pulled out by a pinch roll group 7 while being supported by a slab support roll group 6, and cut by a traveling cutter 8.

The slab support roll group 6 is composed of non-driven rolls that are pressed against the slab 5 and rotate in synchronization with the slab speed, and is connected to one slab support roll 6a on the side of the pinch roll group 7 through a joint. The speed detector 9 is connected, and the slab support roll 6a
The casting speed is detected from the rotation of the

The detection signal is processed by the signal processing circuit 11 together with the signal from the speed command device 10 that gives a speed command to the pinch roll group 7, and as described later, when the change in casting speed becomes larger than the set value, an abnormal signal is generated. is output.

The speed detector 9 is of a high precision pulse type that detects the rotational speed of the slab support roll 6, and its resolution is approximately 0.3 wn/pulse in terms of slab length. The upper limit of this resolution is 1 m+a/pulse in terms of slab length.

In addition, in order to increase the resolution, a speed increaser can be built into the speed detector 9, but even if the apparent accuracy is improved, the backlash of the speed increaser makes it difficult to obtain true speed changes, so this is not recommended. In the example, the resolution was set to 0.3 without using a speed increaser.
I raised it to w/pulse.

The signal processing circuit 11 includes a frequency-voltage converter 11a1, a subtracter 11b, a comparator 11C9, and an abnormality detection level setter lid.

The converter 11a converts the number of pulses from the pulse speed detector 9 into a voltage so that speed changes can be seen as voltage changes, and this voltage VB is input to the subtracter 11b.

The casting speed command voltage VA from the speed command device 10 is also input to the subtractor 11b, and (VB-VA) is subtracted,
As a result, Vc is output. 3 and 4 show the input values VA and VB of this subtracter 11b.

An example of a chart of the output value Vc is shown.

In the comparator 11C, the output voltage Vc from the subtracter 11b
and the set voltage Vs from the abnormality detection level setter, and when the output type jlEvC becomes larger than the set voltage Vs, an abnormality signal is output.0 The above is the basic configuration of the present invention. It has been confirmed that the piece speed changes due to factors other than changes in the frictional force transmitted from the mold to the slab; for example, it has been confirmed that the speed changes instantaneously at the moment the traveling cutter 8 is fixed to or detached from the slab 5. . Therefore, even in normal conditions, the level may exceed the detection level, and there is a possibility that an abnormal signal may be falsely reported. However, since this is instantaneous, it can be avoided by providing a time delay of about 2 seconds from when the cutting machine is attached or detached so as not to detect this, and a highly reliable abnormality signal can be obtained. For this purpose, a time delay element is inserted inside the comparator 11C.

In the above-described configuration, Vc in FIG. 3 is a change that becomes faster or slower than the casting speed command V^, and this signal is the focus of the present invention. The reason why this signal is obtained will be explained below.

The casting speed command V^ is set to obtain the desired casting speed.
This is a command given to the drive motor control device of the pinch roll group 7, and if casting is performed at a constant speed, VA is also a constant voltage. On the other hand, the voltage VB, which represents the actual casting speed, is affected by resistance changes such as the frictional force between the mold and the slab, the resistance force of the slab support rolls, the slab straightening force, etc., and the casting speed fluctuates, compared to VA. The size changes. In particular, vibrations are constantly applied to the mold during casting, and forces act on the slab in the positive and negative directions with respect to the casting direction at vibration cycles. Therefore, compared to other changes in resistance force acting on the slab, it is periodic and its period is short.

When this change in resistance force is applied to the slab, mechanical backlash (
backlash, twist, deflection, etc.)
Even though the pinch roll drive motor rotates according to the change in casting speed, the actual casting speed, ie, VB, varies with the mold vibration period, as shown in FIG. 3. Here, as mentioned above, there are continuous casting machines whose pinch roll drive system has small mechanical play.

The resolution of the speed detector is 1 to 0.31 u/
The present invention works with all continuous casting machines as long as the accuracy is as high as that of a pulse.

Since the frictional force between the mold and the slab is closely related to the state of powder inflow between the mold and the slab, the powder inflow state can be monitored by focusing on the actual casting speed variation Vc. That is, when the powder inflow conditions are good and the frictional force between the mold and the slab is small, the change in casting speed is small.

Conversely, when powder inflow conditions are poor and the frictional force between the mold and the slab is large, the change in casting speed will also be large.

This amount of change varies depending on the continuous casting machine, but in the example carried out by the inventor, it was possible to detect a change of ±20% with respect to the casting speed command, and when the powder inflow conditions were favorable, the change was less than ±5%. It was the amount.

In any case, the powder inflow condition is better as the casting speed is lower. Since the absolute amount of change in Vc is also smaller, the amount of change in Vc obtained at this time is taken as a reference and is proportional to the casting speed. The abnormality detection level is set so that the amount of change is considered to be a normal state, and a case larger than this value is considered to be an abnormality (see FIG. 5).

As described above, it is possible to determine an abnormality in the frictional force at the contact surface between the mold and the slab, and it is possible to predict the occurrence of a breakout.

(Effects of the Invention) As described above, according to the present invention, a speed detector is provided on the slab support roll to directly measure the casting speed and detect changes in the casting speed due to the frictional force between the mold and the slab. Since the condition is monitored based on its size, it is not affected by the mold vibration mechanism as in the past, and there is no disturbance, which is always a problem with strain gauges and accelerometers, making it possible to perform highly reliable monitoring. can.

In addition, there is no need for a complex arithmetic processing circuit for disturbances.
A relatively simple device configuration can be achieved.

Furthermore, since the equipment is installed downstream of the continuous casting machine, maintainability is good.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a device according to the present invention, FIG. 2 is a schematic diagram showing a similar circuit, and FIGS. 3 and 4 are graphs showing each signal. FIG. 4 is an abnormal state, and FIG. 5 is a similar graph, in which (n) and (e) are normal states, and tvt and (V) are abnormal states. 1. Mold, 2. Vibrating table 3. Eccentric cam, 4. Drive motor 5. Slab, 6. Slab supporting roll group 7. Pinch roll group 8. Traveling cutting machine. 9...Speed detector, 10...Speed command unit 11...Signal processing circuit 11a...Frequency voltage converter 11b...Subtractor, 11C...Comparator lid...Abnormality detection level setter No. 3 Fig. 4 figure

Claims (2)

[Claims] (1) In a continuous casting machine, in which the slab cast into a mold is pulled out by a group of pinch rolls while being supported by a group of slab support rolls, the casting speed is directly detected by the rotation of the slab support rolls, and this casting speed is measured. A method for monitoring an abnormality in a mold of a continuous casting machine, characterized in that when the change in the value becomes larger than a set value, it is determined that there is an abnormality in the frictional force at the contact surface between the mold and the slab. (2) In a continuous casting machine that pulls out the slab cast into a mold with a group of pinch rolls while supporting it with a group of slab support rolls, the speed is connected to the slab support roll, detects the casting speed, and outputs the speed. The detector, the speed command device that gives speed commands to the pinch roll group, the detection signal from the speed detector, and the speed command signal from the speed command device are subtracted, and when this subtraction value becomes larger than the set value, 1. An abnormality monitoring device for a mold of a continuous casting machine, comprising a signal processing circuit that outputs an abnormality signal when the abnormality is detected.