GB2054866A

GB2054866A - Electrically monitoring continuous casting oscillations

Info

Publication number: GB2054866A
Application number: GB8020203A
Authority: GB
Original assignee: Centre de Recherches Metallurgiques CRM ASBL
Current assignee: Centre de Recherches Metallurgiques CRM ASBL
Priority date: 1979-06-21
Filing date: 1980-06-20
Publication date: 1981-02-18
Also published as: FR2459095A1; LU82540A1; GB2054866B; BE877175A; AU5949380A; DE3022963A1; SE8004494L; FR2459095B1; ES492631A0; CA1126535A; SE437480B; DE3022963C2; AU534130B2; ZA803690B; BE877173A; JPS566759A; ES8101953A1

Abstract

An output signal derived from a sensor 1 measuring the displacement, speed, or acceleration of a continuous casting mould is compared with an output signal derived from a sensor 2 measuring the displacement, speed, or acceleration of the part of a transmission mechanism adjacent an oscillating drive, in order to detect play in the transmission. The sensor output signals are amplified, filtered and integrated before entering a divider 9 for comparison. <IMAGE>

Description

SPECIFICATION Monitoring continuous casting The present invention relates to a method of monitoring the operation of apparatus for the continuous casting of metals, in particular steel.

We have already proposed a method designed to improve monitoring of the continuous metal casting process, in which the upper surface of the liquid metal in the ingot mould is covered with a protective powder having a suitable composition; the parasitic oscillations of the ingot mould are measured and their spectrum, which is representative of the frictional forces between the strand and the mould, is compared with a predetermined spectrum which is considered to be ideal; the casting parameters are then modified so that the actual spectrum comes as close as possible to the ideal spectrum; at this moment lubrication of the ingot mould is considered to be satisfactory.

It has been observed that, after a continuous casting apparatus has been in use for a time, certain abnormalities in friction, which are difficult to explain on the basis of known modifications or ordinary malfunctions, arise during the continuous casting operation. Consequently the interpretation of such spectrum recordings then became of an unreliable nature.

Experiments and observation have shown that the mechanical elements causing the mould to oscillate are subject to wear in time, as a result of which suitable running of the continuous casting operation was impaired, and therefore the quality of the cast products. In order to remedy this drawback, it may be envisaged to undertake periodic visual inspection of the elements for transmitting movements of oscillation to the mould, but this method is itself unreliable, particularly as it is greatly dependent on the skill of the operator carrying out the inspection.

The present invention provides a method of monitoring the operation of continuous casting apparatus comprising a mould, drive means whose output is a forced oscillation, and a mechanism for transmitting the forced oscillation from the drive means to the mould, the method comprising the steps of measuring the movement of the mould and deriving from the measured movement a first output signal representing the oscillation of the mould, measuring the movement of a part of the said mechanism and deriving from the measured movement a second output signal, comparable to the first output signal, representing the oscillation of the said part, and comparing the first signal with the second signal.

The invention also provides continuous casting apparatus comprising a mould, drive means whose output is a forced oscillation, a mechanism for transmitting the forced oscillation from the drive means to the mould, a first sensor for measuring the movement of the mould, first signal processing means associated with the first sensor for providing a first output signal representing the oscillation of the mould, a second sensorfor measuring the movement of a part of the said mechanism, second signal processing means associated with the second sensor for providing a second output signal, comparable to the first output signal, representing the oscillation of the said part, and means for comparing the first signal with the second signal.

The preferred method will now be described: (a) the actual movements of the mould are measured by means of an appropriate sensor (displacement, speed, or acceleration) rigid with the mould and a determined frequency band is then selected from the frequencies of the movements observed (working signal U); (b) the actual movements of an oscillating arm transmitting the oscillating movement are measured by means of a sensor, preferably located as close as possible to the drive motor generating the oscillation movements of the mould, the sensor being connected with one of the parts for transmitting the movement, and a determined frequency band is then selected from the frequencies of the movements observed (reference signal R);; (c) one, at least, of the two signals U and R has applied to it- (i) a correction factor taking into account (according to a method known per se) the theoretical amplitudes of the oscillating movements at the two points of location of the sensors, and/or (ii) a corrective factor taking into account the intrinsic difference in sensitivity of the sensors, which enables derivation of two comparable output signal U, and R, as well as the values of (U1 - R1)/K and/or U,/R1, in which formulae K = 1 if the sensors are sensors of displacement, K is directly proportional to the forced oscillation frequency if the sensors are sensors of speed, K is directly proportional to the square of the forced oscillation frequency if the sensors are sensors of acceleration;; (d) the signals U and/or R are measured either continuously or periodically, which enables the continuous or periodic variations of the values (U1 - R1)/K and/or U1/R, to be determined and enables the ascertainment of whether these values vary from respective reference values corresponding to a mechanical transmission free of inadmissible play.

It is thus possible to monitor in a permanent way the mechanical condition of the mechanism which causes the mould to oscillate and to provide, within the appropriate time, for maintenance operations to be carried out on the mechanism, when the size of the variation observed between the signals exceeds a level considered as the maximum admissible level in the case in question.

Correction by the factor K may be achieved in a multiplicity of ways, according to the electronic processing to which the initial signals U and R have been preliminarily subjected in deriving the output signals. For example, if an "acceleration type" signal is integrated, correction could then be carried out simply by a K factor of the "speed" type which is directly proportional to the frequency.

Advantageously, the correction factors may be selected such that on starting of the continuous casting operation the signal (U1 - R1)/K is zero, or such that the signal U,/R, is equal tone, which facilitates the assessment of the difference between on one hand these values 0 and 1 and, on the other hand, the instantaneously or periodically measured values of (U1 - R1)/K and/or U,/R,.

A further important advantage of the abovedescribed method is that selective observation of each of the factors U, or R, facilitates the location of a defect (for example in the oscillation arm or in the mould).

The selected frequency band is preferably identical for the two measuring components (the movements of the mould and the oscillation arm) and is selected so as to obtain the greatest possible sensitivity for the measurement. It may be advantageously centered on the forced oscillation frequency, for example between 0 and 5 Hz.

The reference signal R is preferably obtained from a sensor of movement (displacement, speed, or acceleration) applied at a point of the mechanism transmission of the oscillating movement of the mould at which there has been found to be no play.

In addition successive or simultaneous arrangement of sensors at several points of the transmission mechanism would make it possible to rapidly ascertain where the unacceptable play is located in one of the articulations of the transmission.

It should be noted that the above method is also applicable to monitoring the guidance, suspension, and balance of the mould as well, as the oscillation.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 diagrammatically represents a mould and a mechanism for oscillating the mould in a continuous casting apparatus; and Figure 2 is a block diagram of electronic equipment for monitoring the operation of the apparatus.

Referring first to Figure 1, a sensor 1 measures the displacement, the speed, or the acceleration of a continuous casting mould 23 and provides a signal U. A sensor 2 (providing a signal R) measures the displacement, the speed, or the acceleration of a linkage element close to a drive motor 26 having cams, the motor 26 being part of a mechanism 27 for transmitting oscillation to the mould 23. The mould 23 is guided by rollers 24 and rests on suspension springs 25. The method of operation of the continuous casting apparatus is obvious and conventional.

In the electronic equipment shown in Figure 2, an upper sequence starts at the sensor 1, supplied by a block 3. The signal U from the sensor 1 is amplified by an amplifier 5, traverses a band-pass filter 7, and then, optionally after integration (single or double) in an integrator 15, passes into a divider 9 as an input signal U,.

A lower sequence starts at the sensor 2, supplied by a block 4. The signal R from the sensor 2 is amplified by an amplifier 6, traverses a bandpass filter 8, and then, optionally after integration (single or double) in an integrator 16, traverses a corrector device 10 (applying a correction factor to compensate for the difference in sensitivity of the two sensors), and enters the divider 9 as an input signal R,.

The divider 9 provides at its output a signal representing U,/R,, which is amplified by an amplifier 13. The amplified signal is recorded by a graphic instrument 14 and, if necessary, triggers a visual or acoustic alarm 17, 18.

In order to facilitate assessment of the variation between the instantaneous value of the signal U,/R, and a corresponding reference value, a zero suppressor (11-12) is interposed between the divider 9 and the amplifier 13, the purpose of this suppressor being to enable the amplification by the amplifier 1 3 solely of useful variations of the signal U,/R,.

Claims

1. A method of monitoring the operation of continuous casting apparatus comprising a mould, drive means whose output is a forced oscillation, and a mechanism for transmitting the forced oscillation from the drive means to the mould, the method comprising the steps of measuring the movement of the mould and deriving from the measured movement a first output signal representing the oscillation of the mould, measuring the movement of a part of the said mechanism and deriving from the measured movement a second output signal, comparable to the first output signal, representing the oscillation of the said part, and comparing the first signal with the second signal.

2. A method as claimed in claim 1, in which the movement of the mould is measured by measuring the displacement, the speed, or the acceleration of the mould.

3. A method as claimed in claim 1 or 2, in which the movement of the said pair of the mechanism is measured by measuring the displacement, the speed, or the acceleration of the mould.

4. A method as claimed in any of claims 1 to 3, in which the step of deriving the first signal includes band pass filtering the measured movement of the mould.

5. A method as claimed in any of claims 1 to 4, in which the step of deriving the second signal includes band pass filtering the measured movement of the said part of the mechanism.

6. A method as claimed in claim 4 or 5, in which the frequency band of the band pass filtering step is centered on the frequency of the forced oscillation output of the drive means.

7. A method as claimed in any of claims 1 to 6, in which at least one of the steps of deriving the said signals includes applying a correction factor taking into account the difference in amplitude between the oscillation of the mould and the oscillation of the said part of the mechanism assuming that they are connected without play.

8. A method as claimed in any of claims 1 to 7, in which at least one of the steps of deriving the said signals includes applying a correction factor taking account of the difference in sensitivity of the measurements applied to the mould and the said part of the mechanism respectively.

9. A method as claimed in any of claims 1 to 8, in which the first signal and the second signal are derived in such a manner that they are equal in amplitude at the start of the operation of the apparatus.

10. A method as claimed in any of claims 1 to 9, in which the said part of the mechanism is a part which is connected to the drive means without play.

1 A method as claimed in claim 10, in which the said part is adjacent the drive means.

12. A method as claimed in any of claims 1 to 11, further comprising measuring the movement of a further part of the said mechanism.

13. Continuous casting apparatus comprising a mould drive means whose output is a forced oscillation, a mechanism for transmitting the forced oscillation from the drive means to the mould, a first sensor for measuring the movement of the mould, first signal processing means associated with the first sensor for providing a first output signal representing the oscillation of the mould, a second sensor for measuring the movement of a part of the said mechanism, second signal processing means associated with the second sensor for providing a second output signal, comparable to the first output signal, representing the oscillation of the said part, and means for comparing the first signal with the second signal.

14. A method of monitoring the operation of continuous casting apparatus, substantially as described with reference to the accompanying drawings.

1 5. Continuous casting apparatus substantially as described with reference to, and as shown in, the accompanying drawings.