JPH0236163B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus (hereinafter referred to as a shell thickness gauge) for measuring the solidified thickness of a slab during continuous casting using electromagnetic ultrasonic waves.

A conventional device of this type is shown in FIG. In the figure, 1 is an electromagnetic ultrasonic generator, 2 is an electromagnetic ultrasonic receiver, 7 is a slab, 8 is a pulse generation circuit, 9 is an excitation power source, 10 is an amplifier, 11 is a gate circuit, 12 is a transmission time measurement circuit, 13 is a surface thermometer, 14 is a slab total thickness measuring device, 15 is a solidification thickness calculation circuit, and 16 is an output circuit. On the other hand, FIG. 2 is a diagram showing the principle of electromagnetic ultrasonic wave generation and reception in this shell thickness gauge. In this figure, 3 is an electromagnetic ultrasonic generation coil, 4 is an electromagnetic ultrasonic detection coil, 5 is an excitation coil for generating a magnetic field, and 6
is a magnetic core for forming a magnetic circuit. Here, the output 21 of the detection coil 4 is connected to the amplifier 10.

Next, the operation will be explained. Pulse generation circuit 8
The generating coil 3, which is energized with a pulse signal by , generates an eddy current 18. This eddy current 18 further generates a pulsed electromagnetic force due to interaction with the pulsed magnetic field indicated by the arrow 17 according to Fleming's left-hand rule, which causes ultrasonic vibrations on the surface of the slab 7. The above is the principle of electromagnetic ultrasound generation.

Next, the electromagnetic ultrasonic waves generated on the surface of the slab 7 travel inside the slab 7 in the direction of the arrow 19, and when they reach the other side, generate vibrations on the surface of the slab 7. An electromotive force is generated on the surface of the slab 7 due to the interaction between this vibration and the magnetic field created by the excitation coil 5 excited by the excitation power source 9. This is due to Fleming's right-hand rule. This electromotive force generates an eddy current 20 on the surface of the slab 7, and the magnetic field created by this eddy current induces an electromotive force in the detection coil 4 according to Lenz's law, and this electromotive force signal is sent to the amplifier 10 as a received signal.
The signal is amplified and a necessary portion on the time axis is extracted by the gate circuit 11 and sent to the transmission time measuring circuit 13. In this gate circuit 11, a time gate is normally created based on the pulse output timing signal of the pulse generating circuit.

Next, in the transmission time measurement circuit 12, the gate circuit 1
The time t required for the ultrasonic wave to propagate from one side of the slab 7 to the other side of the back side is calculated from the time difference between the received signal input from 1 and the pulse output timing signal, and the result is sent to the solidification thickness calculation circuit 15. It will be done.

Now, suppose that there is an unsolidified part left in the slab, and the thickness of the already solidified part is d = d ₁ + d ₂
Then, the thickness of the unsolidified part should be D-d, so if the speed at which the ultrasonic wave propagates through the solidified area is V _s and the speed at which the ultrasonic wave propagates through the unsolidified area is V _l , then the entire slab The transmission time t for the ultrasonic wave to pass through is expressed as t=d/V _s +D−d/V _l . In general, V _s is the temperature of the ultrasonic propagation velocity based on the solidification temperature of the slab depending on the steel type and the average temperature of the solidified part determined by an average or weighted average from the surface temperature measured by the surface thermometer 13. It is calculated from the dependence characteristics, and since the unsolidified _portion is considered to be in a supercooled state, the value of the ultrasonic propagation velocity in this state is experimentally determined.

Therefore, as input to the solidification thickness calculation circuit 15, in addition to the transmission time t, the thickness information D from the total thickness measuring device 14, the surface temperature information from the surface thermometer 13, and the solidification temperature value of the slab determined by the steel type are input. If the ultrasonic propagation velocity V _l of the unsolidified portion is obtained, the solidified thickness d can be calculated from the above relational expression. The calculated solidification thickness d is displayed or recorded by the output circuit 16.

Since the conventional slab solidification thickness measuring device is configured as described above, it is not possible to exclude accidental noise such as external noise from entering the detection coil side of the electromagnetic ultrasonic receiver. However, it has the disadvantage that it is processed as a received signal, leading to incorrect judgments (erroneous measurements).

This invention was made to eliminate these drawbacks, and by excluding abnormal waveform signals caused by the above-mentioned noise, etc., and further adding statistical processing, it is possible to obtain castings with extremely high measurement accuracy. The present invention provides a piece solidification thickness measuring device.

FIG. 3 is a diagram showing an embodiment of the present invention. In Fig. 3, 1 is an electromagnetic ultrasonic generator, 2
is an electromagnetic ultrasonic receiver, 7 is a slab, 8 is a pulse generation circuit, 9 is an excitation power source, 10 is an amplifier, 11 is a gate circuit, 12 is a transmission time measurement circuit, 22 is a transmission time calculation circuit, and 23 is an abnormal waveform 13 is a surface thermometer, 14 is a slab total thickness measuring device, 15 is a solidification thickness calculation circuit, and 16 is an output circuit.

FIG. 4 is a diagram showing the circuit configurations of the abnormal waveform removal circuit 23 and the transmission time calculation circuit 22. Fourth
In the figure, 24 is an A/D conversion circuit, 25 is a waveform storage circuit, 26 is a maximum amplitude point detection circuit, 27 is a maximum value storage circuit, 28 is a timing control circuit, and 29 is a maximum amplitude point detection circuit.
is a zero cross point detection circuit, 30 is a wavelength calculation circuit, 3
1 is an extreme value point detection circuit, 32 is an extreme value storage circuit, 33
34 is an amplitude ratio calculation circuit, 34 is a wavelength condition determination circuit,
35 is an amplitude condition determination circuit, 36 and 41 are constant setting circuits, 37 is a waveform information storage circuit, 38 is a wavelength average value calculation circuit, 39 is an amplitude average value calculation circuit, 4
0 is a comparison judgment circuit, 42 is a transmission timing signal,
43 is a received signal, 44 is a transmission time signal, 45 is a data valid signal, 46 is a transmission time storage circuit, 47 is a valid data determination circuit, 48 is an average value calculation circuit, 4
9 is an average transmission time signal.

Next, the operation of an embodiment of the present invention shown in FIGS. 3 and 4 will be described. A transmission timing signal 42 synchronized with the transmission signal to the electromagnetic ultrasonic generator 1 is outputted by the pulse generation circuit 8 and inputted to the transmission time measurement circuit 12 and the abnormal waveform removal circuit 23. On the other hand, the received signal 43 from the electromagnetic ultrasonic receiver 2, which is excited by the excitation power source 9 and becomes receivable, is amplified by the amplifier 10, and the gate circuit 1
1, only necessary signals are time-discriminated and input to the transmission time measuring circuit 12 and the abnormal waveform removing circuit 23. The transmission time measurement circuit 12 calculates the transmission time t _T from the time difference between the transmission timing signal 42 and the reception signal 43, sends it as a transmission time signal 44 to the transmission time calculation circuit 22, and stores it in the transmission time storage circuit 46. Make me remember.

Now, in the abnormal waveform removal circuit 23, the above-mentioned received signal 43 is first inputted to the A/D conversion circuit 24,
The signals are sampled at timings instructed by the timing control circuit 28, converted to digital values, and stored in the waveform storage circuit 25 in time series. Note that the timing control circuit 28 performs timing control in conjunction with the transmission timing signal 42 so that the entire waveform of the reception signal 43 is sufficiently stored.

FIG. 5 shows an example of the received signal 43 stored in the waveform storage circuit 25 as described above. Although the waveforms are shown as analog waveforms in FIG. 5, they are actually stored as digital values arranged in time series. When the storage of the received signal 43 is completed, the timing control circuit 28 next indicates that
The data is read out in order, and the maximum amplitude point detection circuit 2
6, the time t _M that gives the maximum amplitude is detected,
At the same time, the maximum value storage circuit 27 stores the amplitude value V _M at this time. Note that the waveform storage circuit 25
is designed to store data in chronological order,
Furthermore, data sampling is also performed at a known timing predetermined by the timing control circuit 28, so by knowing the position of the data stored in the waveform storage circuit 25, the above-mentioned time _tM can be easily determined. Desired.

Next, when time t _M is detected by the maximum amplitude point detection circuit 26, this information is transmitted to the timing control circuit 26.
Enter 8. The timing control circuit 28
From the position on the waveform storage circuit 25 corresponding to t _M , data is read out in the backward and downward directions in time, and zero cross times t _Z-2 to t _Z2 in a preset range before and after time t _M are read out. Also, times t _P-2 to t _P2 indicating the local maximum value and local minimum value are detected by the zero cross point detection circuit 29 and the extreme value point detection circuit 31, respectively. The wavelength calculation circuit 30 calculates the wavelength from the above zero-crossing time, for example, as λ=t _Z1 to t _Z-2 . Of course, when determining the wavelength λ, for example, λ is expressed as t Z-2 , t _Z-1 , t _Z1 , λ = (λ _Z1 - _{λ Z-2} + λ _Z2 - _{λ Z-1 )} /2 Other statistical calculation methods may be introduced as a function of t _Z2 .

The extreme value storage circuit 32 stores the amplitude values V P-2 to V _P2 at each of the extreme points t _P-2 to t P2 detected by the extreme value point detection circuit 31, and stores the amplitude values V P-2 to V P2 at each of the extreme value points _{t P-2} to t _P2 detected by the extreme value point detection circuit 31. is determined by the amplitude value V _M stored in the maximum value storage circuit 27 and these V _P-2 to V _P2 , for example, the respective amplitude ratio k _i to V _M = V _Pi /
Find V _M (i=-2 to 2). Of course, other arithmetic processing may be performed on this amplitude ratio, such as finding it as a matrix consisting of V _M , V _P-2 to V _P2 .

The wavelength condition determination circuit 34 determines whether the wavelength λ calculated by the wavelength calculation circuit 30 is within a range preset by the constant setting circuit 36,
Remove data that does not satisfy this condition. Similarly, the amplitude condition determination circuit 35 determines whether or not the data should be discarded based on whether the amplitude ratio k _-2 to _{k 2} obtained by the amplitude ratio calculation circuit 33 satisfies the condition set in advance by the constant setting circuit 36. Do the following. Therefore, only data that satisfies the setting conditions set by the constant setting circuit 36 passes through the wavelength condition determination circuit 34 and the amplitude condition determination circuit 35, and is stored in the waveform information storage circuit 37.
It can be stored in

If the process up to this point is repeated for N receptions, the waveform information storage circuit 37 will contain K pieces of wavelength data (only K
≦N) wavelength data λ _i (i=1 to K) and amplitude ratio data k _P-2i to k _P2i (i=1 to K) are stored.

When the N times of reception are completed, the K pieces of data stored in the waveform information storage circuit 37 are sequentially read out according to instructions from the timing control circuit 28, and the wavelength average value calculation circuit 38 and the amplitude average value calculation circuit 39
Accordingly, the respective average values _P-2 to _P2 are calculated and sent to the comparison/judgment circuit 40.

The timing control circuit 28 reads the data from the wavelength information storage circuit 37 again after the wavelength average value calculation circuit 38 and the amplitude average value calculation circuit 39 send their respective average values to the comparison judgment circuit 40, and then reads the data from the wavelength information storage circuit 37 again. 40 represents these data λ _i ,
Compare k _P-2i to k _P2i (i = 1 to K) with the above-mentioned average value, _P-2 to k ^P2 , and select the data that falls within the deviation value preset by the constant setting circuit 41. The data valid signal 45 is output only for the data.

Here, among the N times of transmission time data t _Ti (i=1 to N) stored in the transmission time storage circuit 46, the transmission time data t _Tj (j=1 to N) corresponding to the data valid signal 45 is K) only passes through the transmission time determination circuit 47, and the average transmission time value _T is calculated by the average value calculation circuit 48, and is sent to the coagulation thickness calculation circuit 15 as an average transmission time signal 49.

The solidification thickness calculation circuit 15 calculates the average transmission time t= _T by the transmission time calculation circuit 22 and the surface thermometer 1.
3 and the total thickness D measured by the slab total thickness measuring device 14, the solidified thickness is determined in the same manner as the conventional calculation method, and is outputted to the outside by the output circuit 16.

In this embodiment, the set value of the constant setting circuit 36 is
For example, the set value of the constant setting circuit 41 is set to be ±10% with respect to the wavelength and amplitude ratio expected in advance, and the set value of the constant setting circuit 41 is similarly set with respect to the above average value λ, k _P-2 to _{k P2} . By setting, for example, ±3%, it was possible to very effectively remove short wavelength waveforms with steep rises due to inrush currents of motors and electromagnetic switches, etc., without damaging useful data.

Although the above explanation has been based on a digital circuit that handles digitized data, it is not possible to replace part or all of this circuit with an analog circuit, or replace it with software using a computer. Of course, this is possible, and the spirit of the present invention is not detracted from it in any way. In addition, in this embodiment, the extreme value points and zero cross points are t _P-2 to t _P2 and t _Z-2, respectively.
Although the explanation has been made using eight points of ~t _Z2 , the present invention is not limited to this, and does not particularly limit the number of extreme value points and zero cross points, and various modifications can be made without departing from the gist of the present invention. .

Furthermore, the abnormal waveform removal circuit and transmission time calculation circuit according to the present invention can be applied not only to shell thickness gauges but also to other transmitting and receiving devices that utilize propagation of ultrasonic waves, such as wall thickness gauges and thermometers.

As described above, according to the present invention, abnormal waveform signals generated due to accidental noise such as external noise being mixed into the detection coil side of an electromagnetic ultrasonic receiver are excluded, and further statistical processing is performed. By adding this, it is possible to measure the solidified slab thickness with extremely high measurement accuracy.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a conventional slab solidification thickness measuring device, Figure 2 is a diagram showing the principle of electromagnetic ultrasonic generation and reception, and Figure 3 is a diagram showing the configuration of an embodiment of the device of the present invention. 4 is a block diagram showing the circuit configuration of the abnormal waveform removal circuit and the transmission time calculation circuit of the device of the present invention, and FIG. 5 is a diagram showing an example of a received signal obtained by the device of the present invention. In the figure, 1 is an electromagnetic ultrasound generator, 2 is an electromagnetic ultrasound receiver, 3 is an electromagnetic ultrasound generation coil, 4 is an electromagnetic ultrasound detection coil, 5 is an excitation coil, 6 is a magnetic core, and 7
1 is a slab, 8 is a pulse generation circuit, 9 is an excitation power source, 1
0 is an amplifier, 11 is a gate circuit, 12 is a transmission time measuring circuit, 13 is a surface thermometer, 14 is a slab total thickness measuring device, 15 is a solidification thickness calculation circuit, 16 is an output circuit, 17 is a pulsed magnetic field, 18 and 20 is an eddy current, 19 is the propagation direction of the ultrasonic wave, 21 is the output of the electromagnetic ultrasonic detection coil 4, 22 is a transmission time calculation circuit,
23 is an abnormal waveform removal circuit, 24 is an A/D conversion circuit, 25 is a waveform storage circuit, 26 is a maximum amplitude point detection circuit, 27 is a maximum value storage circuit, 28 is a timing control circuit, 29 is a zero cross point detection circuit, 30 is a wavelength calculation circuit, 31 is an extreme point detection circuit, 32 is an extreme value storage circuit, 33 is an amplitude ratio calculation circuit, 34 is a wavelength condition determination circuit, 35 is an amplitude condition determination circuit, 36 and 41 are constant setting circuits, , 37 is a waveform information storage circuit, 38 is a wavelength average value calculation circuit, 39 is an amplitude average value calculation circuit, 40 is a comparison judgment circuit, 42 is a transmission timing signal, 43 is a reception signal, 44 is a transmission time signal, and 45 is data. 46 is a transmission time storage circuit, 47 is a valid data determination circuit, 48 is an average value calculation circuit, and 49 is an average transmission time signal.
In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Scope of Claims] 1. An electromagnetic ultrasonic generator that is installed on one surface of a slab to be continuously cast and is equipped with a coil to which a high-frequency pulse current is applied to generate ultrasonic waves on the surface of the slab; An electromagnetic ultrasonic receiver equipped with a detection coil installed on the other side of the slab to receive the ultrasonic waves, and an ultrasonic wave generation and reception timing of the ultrasonic generator and receiver described above to ultrasonicate the slab. a time measuring circuit for determining the time t required for propagation from the one surface to the other surface; a total thickness measuring device for measuring the total thickness D of the slab; and the time t measured by the time measuring circuit; The total thickness D measured by the total thickness measuring device, the speed Vs at which the ultrasonic wave propagates through the solidified part of the slab with thickness d, and the ultrasonic wave propagates through the unsolidified part of the slab with thickness D-d. Speed Vl
and an arithmetic circuit for calculating a solidified portion thickness d from a waveform storage circuit for storing received signals received by the electromagnetic ultrasonic receiver in time series; A maximum amplitude checking circuit detects a time t _M indicating the maximum amplitude of the received signal stored in the circuit, and a zero cross time in a preset range around time t _M is determined from the received signal stored in the waveform storage circuit. A zero cross inspection circuit for detecting a zero cross, a wavelength calculation circuit for calculating a wavelength λ using the zero cross time, and a wavelength calculation circuit for determining whether the wavelength λ calculated by the wavelength calculation circuit λ is within a preset range. a wavelength condition determination circuit that removes data that does not satisfy the conditions; a waveform information storage circuit that stores wavelength data that satisfies the setting conditions output from the wavelength condition determination circuit; and a plurality of waveform information stored in the waveform information storage circuit. A wavelength average value calculation circuit inputs the wavelength data of and calculates the average value, and compares the output data from the waveform information storage circuit with the output data from the wavelength average value calculation circuit, and calculates a preset deviation. The solidified slab thickness is characterized in that an abnormal waveform removal circuit is provided between the electromagnetic ultrasonic receiver and the time measurement circuit and includes a comparison judgment circuit that outputs a data valid signal only for data that falls within a value. measuring device. 2. An electromagnetic ultrasonic generator installed on one side of the slab to be continuously cast and equipped with a coil to which a high-frequency pulse current is applied to generate ultrasonic waves on the surface of the slab, and installed on the other side of the slab. and an electromagnetic ultrasonic receiver equipped with a detection coil that receives the ultrasonic waves, and an ultrasonic wave that moves the slab from one side to the other based on the timing of ultrasonic generation and reception of the ultrasonic generator and receiver. a time measuring circuit for determining the time t required for the slab to propagate; a total thickness measuring device for measuring the total thickness D of the slab; and a time measuring circuit for determining the time t required for the slab to propagate to the measured total thickness D, the speed Vs at which the ultrasonic wave propagates through the solidified part of the slab having a thickness d, and the speed Vl at which the ultrasonic wave propagates through the unsolidified part of the slab thickness D-d.
and an arithmetic circuit that calculates the solidified portion thickness d from the waveform storage circuit that stores the received signal received by the electromagnetic ultrasonic receiver in time series, and the waveform a maximum amplitude point detection circuit that detects a time t _M indicating the maximum amplitude of the received signal stored in the storage circuit; a maximum value storage circuit that stores the amplitude value V _M at the time t _M ; and a maximum amplitude point detection circuit that stores the amplitude value V M at the time t M; an extreme point detection circuit that detects the times at which local maximum and local minimum values occur in a preset range before and after time t _M from the received signal; An extreme value storage circuit that stores amplitude values, and an amplitude value using the amplitude value V _M stored in the maximum value storage circuit and the amplitude value stored in the extreme value storage circuit.
An amplitude ratio calculation circuit that calculates each amplitude ratio with respect to V _M , and an amplitude condition judgment that determines whether or not data is to be discarded depending on whether the amplitude ratio calculated by the amplitude ratio calculation circuit satisfies a preset condition. A circuit, a waveform information storage circuit that stores amplitude data that satisfies the setting conditions output from the amplitude condition determination circuit, and a plurality of pieces of amplitude data stored in the waveform information storage circuit are input, and the average value thereof is calculated. The output data from the amplitude average value calculation circuit and the waveform information storage circuit are compared with the output data from the amplitude average value calculation circuit, and only data that falls within a preset deviation value is sent as a data valid signal. 1. An apparatus for measuring the solidification thickness of a slab, characterized in that an abnormal waveform removal circuit including a comparison and determination circuit that outputs the following is provided between the electromagnetic ultrasonic receiver and the time measurement circuit. 3. An electromagnetic ultrasonic generator installed on one side of the slab to be continuously cast and equipped with a coil to which a high-frequency pulse current is applied to generate ultrasonic waves on the surface of the slab, and installed on the other side of the slab. and an electromagnetic ultrasonic receiver equipped with a detection coil that receives the ultrasonic waves, and an ultrasonic wave that moves the slab from one side to the other based on the timing of ultrasonic generation and reception of the ultrasonic generator and receiver. a time measuring circuit for determining the time t required for the slab to propagate; a total thickness measuring device for measuring the total thickness D of the slab; and a time measuring circuit for determining the time t required for the slab to propagate to the measured total thickness D, the speed Vs at which the ultrasonic wave propagates through the solidified part of the slab having a thickness d, and the speed Vl at which the ultrasonic wave propagates through the unsolidified part of the slab thickness D-d.
and an arithmetic circuit for calculating a solidified portion thickness d from a waveform storage circuit that stores received signals received by the electromagnetic ultrasonic receiver in time series. a maximum amplitude point detection circuit that detects a time t _M indicating the maximum amplitude of the received signal stored in the waveform storage circuit; a maximum value storage circuit that stores the amplitude value V _M at the time t _M ; a zero-crossing point detection circuit and an extreme point detection circuit for detecting zero-crossing times, local maximum values, and local minimum values in a preset range before and after time t _M from a received signal stored in a storage circuit; a wavelength calculation circuit that calculates the wavelength λ using the zero crossing time; an extreme value storage circuit that stores the amplitude value at the extreme point detected by the extreme point detection circuit; and an amplitude value stored in the maximum value storage circuit. an amplitude ratio calculation circuit that calculates the respective amplitude ratios to the amplitude value V _M using the amplitude value V _M at which the current value is stored and the amplitude value stored in the extreme value storage circuit; a wavelength condition determination circuit that determines whether the wavelength falls within a preset range and removes data that does not satisfy this condition;
an amplitude condition determination circuit that determines whether or not data is to be discarded depending on whether the amplitude ratio obtained by the amplitude ratio calculation circuit satisfies a preset condition; outputs from the wavelength condition determination circuit and the amplitude condition determination circuit; a waveform information storage circuit that stores wavelength data and amplitude data that satisfy the setting conditions set by the wavelength information storage circuit; The output data from the average value calculation circuit, the amplitude average value calculation circuit, and the waveform information storage circuit are compared with the output data from the wavelength average value calculation circuit and the amplitude average value calculation circuit, and the output data is determined to be within a preset deviation value. A slab solidification thickness measuring device, characterized in that an abnormal waveform removal circuit including a comparison judgment circuit that outputs a data valid signal only for input data is provided between the electromagnetic ultrasonic receiver and the time measurement circuit.