JPH07115138B2 - Continuous casting machine Mold abnormality monitoring method and equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for monitoring abnormalities in a continuous casting machine mold.

(Prior art and its problems) Generally, surface flaws such as vertical cracks that occur on the surface of a cast piece cast in continuous casting of steel are greatly affected by the initial solidification state in the mold, and especially between the mold and the cast piece. It is well known that there is a close relationship with the inflowing mold powder, and defects tend to occur when showing a non-uniform inflow situation, and breakout tends to occur at such times. There has been proposed a method of detecting and monitoring the inflow state of the steel as a frictional force between the mold and the slab (JP-A-57-68256, JP-A-57-112962, JP-A-60-12105).
No. 7).

However, these conventional methods have major problems. First, in the method of attaching a strain gauge or accelerometer to the mold vibration generating mechanism and detecting the frictional force between the mold and the slab as a change in stress or a disturbance in the mold vibration waveform, the mold vibration generating mechanism generally has high rigidity, The change in the frictional force between the slabs does not appear in the measured values. Therefore, we use high-sensitivity strain gauges and accelerometers, but the vibration of the continuous casting machine itself (for example, the vibration due to the water flow of the mold cooling water) is high, and the measurement has a lot of disturbances. When it is attached, the desired signal is also attenuated at the same time, which results in unreliable measurement, which is not practical.

Further, as another method, a method of using a load cell has been proposed, but as described above, the difference between the frictional force in the normal state and the frictional force in the abnormal state cannot be detected by the load cell, I can't put it into practice.

In addition, there is another plan to measure the thickness of the powder film by attaching an ultrasonic sensor etc. to the back surface of the mold that directly contacts the slab, and to measure the powder inflow situation, but the disturbance due to the vibration of the water flow However, it is not practical in terms of maintainability.

The present invention has been proposed in view of such circumstances, and an object thereof is a continuous casting machine that can be put to practical use in terms of disturbance and maintainability of a detector, and can perform highly reliable monitoring. An object is to provide a mold abnormality monitoring method and apparatus.

(Means and Actions for Solving Problems) A method for monitoring abnormality of a continuous casting machine mold according to the present invention is that a cast piece cast in a mold is pulled out by a pinch roll group while being supported by a cast piece support roll group. In the anomaly monitoring method for monitoring anomalies in the mold of a continuous casting machine, the fact that changes in the frictional force between the mold and the slab, which depend on the flow of mold powder, appears as changes in the slab speed is used. By following the rotation of the roll, the casting speed including the minute speed change based on the mold vibration is directly detected, the casting speed change based on the mold vibration is calculated from the actual casting speed and the casting speed command, and the casting speed change is calculated. However, when the powder inflow between the mold and the slab is greater than the set value set using the casting speed change when the situation is good, it is judged that the frictional force at the contact surface between the mold and the slab is abnormal. It is obtained so as to perform monitoring of reliable template.

Next, the anomaly monitoring apparatus according to the present invention, in the anomaly monitoring apparatus for monitoring the anomaly in the mold of the continuous casting machine that pulls out the slab cast in the mold by the pinch roll group while supporting the slab supporting roll group. , The speed that is connected to the slab support roll that rotates following and has the resolution that can detect the minute slab speed change based on the mold vibration, and the speed that detects and outputs the casting speed including the minute speed change based on the mold vibration. Casting based on mold vibration by subtracting the detector, the speed commander that gives the casting speed command to the pinch roll group, the actual casting speed detection signal from the speed detector, and the casting speed command signal from the speed commander Obtain the speed change amount and compare this subtracted value with the set value set using the casting speed change amount when the powder inflow condition between the mold and the slab is good, and the subtracted value becomes larger than the set value. When an error occurs And a signal processing circuit for outputting a signal, which does not require a complicated arithmetic processing circuit as in the prior art and enables highly reliable monitoring of the mold with a relatively simple structure.

(Example) Hereinafter, the present invention will be described based on an illustrated example.

As shown in FIG. 1, the mold 1 is vibrated by the drive motor 4 through the eccentric cam 3 and the vibration table 2, and the cast slab 5 is supported by the slab supporting roll group 6 and the pinch roll group. It is pulled out by 7, and cut by the traveling type cutting machine 8.

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

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

The speed detector 9 is a high-precision pulse type that detects the rotation speed of the slab support roll 6, and its resolution is the slab length.
It is about 0.3 mm / pulse. The upper limit of this resolution is 1 mm / pulse in terms of the length of the slab, and to increase the resolution,
Although a speed increaser can be built in the speed detector 9, it is difficult to obtain a true speed change due to the backlash of the speed increaser even if the accuracy is apparently improved. Therefore, in this embodiment, the speed increaser is not used. Increased resolution to 0.3 mm / pulse.

The signal processing circuit 11 includes a frequency voltage converter 11a, a subtractor 11b,
It comprises a comparator 11c and an abnormality detection level setting device 11d.

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

The subtractor 11b includes a casting speed command voltage V from the speed command device 10.
A is also input and (VB-VA) is subtracted, resulting in Vc
Is output. 3 and 4 show the input value V of this subtractor 11b.
A chart example of A, VB, and output value Vc is shown.

The comparator 11c compares the output voltage Vc from the subtractor 11b with the set voltage Vs from the abnormality detection level setter, and outputs the output voltage
When Vc becomes larger than the set voltage Vs, an abnormal signal is output.

The above is the basic configuration of the present invention, but the slab speed also changes in addition to the change in the frictional force transmitted from the mold to the slab, and for example, at the moment when the traveling cutting machine 8 is fixed to the slab 5, or when the traveling cutting machine 8 is detached. It has been confirmed that the speed changes momentarily. Therefore, there is a possibility that the abnormal level may be falsely reported because the detection level becomes higher than the detection level even in the normal state. However, since it is instantaneous, it can be avoided by detecting it with a time delay of about 2 seconds from the time of attachment / detachment of the cutting machine so that an abnormal signal with high reliability can be obtained. For this purpose comparator 11
c A time delay element is inserted inside.

In the above-mentioned structure, Vc in FIG. 3 is a change amount that is faster or slower than the casting speed command VA, and this signal is the most noticeable part of the present invention. The reason why this signal is obtained will be described below.

The casting speed command VA is a command given to the drive motor controller of the pinch roll group 7 in order to obtain a desired casting speed, and VA is also a constant voltage if casting is performed at a constant speed. On the other hand, the voltage VB, which represents the actual casting speed, is affected by the frictional force between the mold and the slab, the resistance change of the slab support roll, the slab straightening force, etc., and the casting speed fluctuates. Change in size. In particular, vibration is constantly applied to the mold during casting, and forces in the forward and reverse directions with respect to the casting direction act on the slab in a vibration cycle. Therefore, the cycle is shorter and shorter than other changes in the resistance force acting on the slab.

When this change in resistance is applied to the slab, the pinch roll drive motor that controls the casting speed has mechanical play (backlash, twist, deflection, etc.) in the drive system. The actual casting speed, that is, VB, fluctuates with the mold vibration period even if the rotation is performed according to the speed command, as shown in FIG. Here, there is a continuous casting machine with a small mechanical backlash of the pinch roll drive system, but as described above, the resolution of the speed detector is 1 to 0.3 m in terms of the length of the cast piece.
The present invention can be applied to all continuous casting machines if the accuracy is as high as m / pulse.

Since the frictional force between the mold and the slab is closely related to the inflow condition of the powder flowing between the mold and the slab, the powder inflow condition can be monitored by focusing on the actual casting speed change Vc. That is, when the powder inflow condition is good and the frictional force between the mold and the slab is small, the change in casting speed is small. On the contrary, when the powder inflow situation is poor and the frictional force between the mold and the slab is large, the change in casting speed also becomes large.

This change amount varies depending on the continuous casting machine, but in the example implemented by the inventor, a change amount of ± 20% can be detected with respect to the casting speed command, and ± 5% or less when the powder inflow situation is good. Was the amount of change.

In any case, the condition of the powder inflow condition becomes better as the casting speed becomes lower, and the absolute amount of change in Vc also becomes smaller.Therefore, the change in Vc obtained in proportion to the casting speed with reference to the change amount at this time The abnormality detection level is set such that the amount is in a normal state and an abnormality is detected when the amount is larger than this value (see FIG. 5).

From the above, it is possible to judge the abnormality of the frictional force at the contact surface between the mold and the slab, and to predict the occurrence of breakout.

(Effect of the Invention) As described above, according to the present invention, a speed detector is provided on the slab support roll, the casting speed is directly measured, and the change in the casting speed due to the frictional force between the mold and the slab is detected. Since the condition is monitored according to the size, it does not depend on the mold vibration mechanism as in the past, and there is no disturbance that is always a problem with strain gauges and accelerometers, and highly reliable monitoring is possible. You can

In addition, it does not require a complicated arithmetic processing circuit for disturbance,
The device configuration can be relatively simple.

Further, since the device is installed on the downstream side of the continuous casting machine, maintainability is good.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a device according to the present invention, FIG. 2 is a schematic diagram showing a similar circuit, FIGS. 3 and 4 are graphs showing respective signals, and FIG. FIG. 4 is an abnormal state, and FIG. 5 is a similar graph. (Ii) and (iii) are normal states, and (iv) and (v) are abnormal states. 1 ... Mold, 2 ... Vibration table 3 ... Eccentric cam, 4 ... Drive motor 5 ... Cast, 6 ... Cast support roll group 7 ... Pinch roll group 8 ... Traveling cutting machine 9 ...... Speed detector, 10 …… Speed commander 11 …… Signal processing circuit 11a …… Frequency voltage converter 11b …… Subtractor, 11c …… Comparator 11d …… Abnormality detection level setter

Claims (2)

[Claims] 1. An abnormality monitoring method for monitoring an abnormality in a mold of a continuous casting machine, wherein a slab cast in a mold is supported by a slab support roll group while being pulled out by a pinch roll group. The rotation directly detects the casting speed that includes a minute speed change based on the mold vibration, and determines the casting speed change based on the mold vibration from the actual casting speed and the casting speed command. When the powder inflow condition between the slab and the slab becomes larger than the set value set using the casting speed change when the situation is good, it is judged that the friction force at the contact surface between the mold and the slab is abnormal. Continuous casting machine Mold abnormality monitoring method. 2. An abnormality monitoring device for monitoring an abnormality in a mold of a continuous casting machine, wherein a slab cast in a mold is supported by a slab support roll group while being pulled out by a pinch roll group. A pinch roll group, which is connected to a roll and has a resolution capable of detecting minute casting slab speed changes based on mold vibration, and which detects and outputs the casting speed including minute speed changes based on mold vibration. The speed commander that gives the casting speed command, the actual casting speed detection signal from the speed detector, and the casting speed command signal from the speed commander are subtracted to obtain the casting speed change based on the mold vibration. Compares the subtracted value with the set value set using the casting speed change when the powder inflow condition between the mold and the slab is good, and outputs an abnormal signal when the subtracted value becomes larger than the set value. Signal processing times It was composed of a malfunction monitoring apparatus for a continuous casting machine mold, characterized in.