LU82540A1 - IMPROVEMENTS IN PROCESSES FOR MONITORING THE CONTINUOUS CASTING OF METALS, ESPECIALLY STEEL - Google Patents

Description

I Claim of priority 1 jp of a patent application filed / y in Belgium on 21.6.1979 under NO 877.173 c 1957E / 8006.

BL-2890 Λ

PATENT

METALLURGICAL RESEARCH CENTER -CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Non-profit association - vereniging zonder winstoogmerk in BRUXELLES, (Belgium).

Improvements to the continuous casting control methods for metals, especially steel.

The present invention relates to improvements to the methods for controlling the continuous casting of metals, and in particular steel.

The same applicant has already described a method for improving the control of the process of continuous casting of metals, in which the upper surface of the liquid metal in the mold is covered with a protective powder of composition (suitable; in this method , the parasitic oscillations of the ingot mold are recorded, the spectrum of which is compared, which is representative of the friction forces between ingot and jh * /.

Si. - ingot mold with another spectrum considered to be ideal and the casting parameters are modified, so that the real spectrum is as close as possible to the ideal spectrum; at this time, the lubrication of the mold is considered satisfactory.

However, it was found that after a certain time of use of a continuous casting installation, the frictions presented anomalies which are difficult to explain from> known modifications or common incidents which appeared during the course of the operation. continuous casting. It followed that the correct interpretation of this recording then became questionable.

Experience and observation have then shown that over time there is wear in the mechanical organs transmitting the oscillation to the ingot mold, which had the effect of compromising the smooth running of the continuous casting operation, and therefore the quality of the cast products.

To overcome this drawback, one can imagine to regularly carry out visual inspections of the organs for transmitting the oscillation movement to the ingot mold, but this way of proceeding is itself questionable, especially because it depends very much on the operator responsible for control.

The present invention relates to a per-1 method which overcomes this drawback.

The process which is the subject of the present invention is essential.

Itially characterized in that: a. b the actual movements of the ingot mold are measured, using an appropriate sensor, integral with the ingot mold (displacement, speed or acceleration) and which is then selected from the I frequencies of the movements observed a frequency band well determined (useful signal U) b. measuring the real movements of the swing arm trans-, putting the movement, using a sensor preferably located / as close as possible to the drive motor generating ώ · '' "f 3. - i I oscillating movements of the ingot mold, sensors in connection i with one of the transmission members of said movement and a well-defined frequency band is selected from the frequencies of the movements observed (reference signal R) ,

jç. one affects at least one of the two signals U and R

- a corrective term taking into account (according to a method well known per se) the theoretical amplitudes of the oscillatory movements at the two places where said sensors are placed, - and / or a corrective term taking into account the difference in intrinsic sensitivity of the two sensors, which makes it possible to calculate two corrected signals and R ^ as well as the values of U1 - R1 and / or of ^ 1, formulas in which: K R1 K = 1 if the sensors are displacement sensors, K is directly proportional to the oscillation frequency of the mold, if the sensors are speed sensors, K is directly proportional to the square of the oscillation frequency of the mold, if the sensors are acceleration sensors.

cl. the signals U and / or R are measured continuously or periodically, which makes it possible to determine the continuous or periodic variations in the values of U1 - R1 and / or ul, and to note whether

K

these values deviate from the reference values corresponding to a mechanical transmission free from unacceptable play.

i

We can thus monitor, permanently, the mechanical state of the device ensuring the oscillation of the mold and plan, in due time, the maintenance operations to be carried out on this device, when the quantity representing the measurement carried out, exceeds a determined level considered as the maximum admissible in the case considered.

Correction by factor K can be carried out in many ways, depending on the electronic processing to which the! U and R signals would have been previously submitted. For example, if one integrates a signal "acceleration type" then it would be necessary to correct only by a factor K of the type "speed", directly proportional to the frequency.

* Advantageously, the corrective terms can be chosen so that at the start of the start of the casting operation the signal (U1 - Rl) is zero, or the signal is equal to unity, which facilitates the appreciation of the difference presented between on the one hand, these values O or 1 and on the other hand the instantaneous or periodic measured values, of (* 1 - Rl) and / or K Rl

Another important advantage of the process of the invention consists in the fact that the selective observation of each of the terms or facilitates the localization of a defect (for example on the oscillation arm side or the ingot mold side).

The frequency band chosen is preferably identical for the two components for measuring the movements of the ingot mold and the oscillation arm and is chosen so as to obtain the greatest possible sensitivity for the measurement. It i can advantageously be centered on the frequency of forced oscillation of the mold, for example between 0 and 5 Hertz.

According to a variant of the method of the invention, the reference signal is obtained from an appropriate motion sensor (displacement, speed or acceleration) applied at a point in the mechanical transmission of the oscillatory movement of the mold where the we found that there was no play.

In addition, it does not depart from the field of the invention, to have sensors successively or simultaneously in several places of the transmission, in order to quickly determine where an unacceptable clearance can be found in one of the articulations of said transmission.

It should be noted that the above process also applies to the control of the guide, the suspension and the balance of the mold, as well as of the oscillation table.

(î 5 · ~ 5 I The diagrams below, given by way of non-limiting example, make it possible to understand how the process of the invention can be implemented.

. Figure 1 relates to the mechanical part of a device for this implementation. FIG. 2 relates * to a block diagram relating to an electronic apparatus allowing the abovementioned measurements.

In FIG. 1 are represented in 1 the displacement or speed sensor, or acceleration of the ingot mold 3 and delivering the signal U. In 2 is the sensor (delivering the signal R) of the displacement, or speed or acceleration of an element close to the eccentric control motor 6, element forming part of the transmission system (shown diagrammatically in 7) of the oscillating

Ition in the mold. This ingot mold is guided by rollers 4 and rests on suspension springs 5. The operating mode of this device is self-explanatory.

The electronic diagram shown in Figure 2 is described as follows.

The upper chain comprises at 1 the sensor U, supplied by the block 3. The signal U amplified at 5, passes through a bandpass filter 7, then, after possible integration (single or double at 15) enters a divider 9.

The lower chain comprises in 2 the sensor R, supplied by the block 4. The signal R amplified in 6, crosses a filter ♦ bandpass 8, then, after possible integration (single or double S in 16), crosses a device corrector (correction factor!) 10 and enters divisor 9.

This divider 9 delivers at its output a signal representing i, which is amplified at 13 to finally be enre-R1 recorded at 14 and if necessary activate an alarm signal 17-18, visual or acoustic.

jL

k ',, [In order to facilitate the assessment of the existing gap

U

between the instantaneous value of 1 and the corresponding value

R

for reference, there is interposed 1 between the divider 9 and the amplifier 13, a zero suppressor (11-12), the purpose of which is to allow the only amplification by the block 13 of the useful variations * of the signal ^ _1.

; 7p L --- · d

Claims (5)

2. Method according to claim 1, characterized in that the corrective terms are chosen so that at the start of the start of the casting operation the signal (U1 - Rl) is zero, or that the signal U1 is equal to 1 '... K unit. 3. Method according to either of claims 1 and 2, characterized in that the frequency band is centered on the frequency of forced oscillation of the mold, for example between 0 and 5 Hertz. 4. Method according to either of claims 1 to 3, characterized in that the reference signal is obtained from an appropriate motion sensor (displacement, speed or acceleration) applied at a location in the transmission mechanics of the oscillatory movement in the mold where it was found that there was no play. 5. Method according to either of claims 1 to 4, characterized in that there are successively or simultaneously motion sensors in several places of the transmission. 6. Processes as described above. _ "ru 'c