GB2068803A

GB2068803A - Monitoring of continuous casting processes to obviate breakdowns or fracture of the casting

Info

Publication number: GB2068803A
Application number: GB8104613A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1980-02-13
Filing date: 1981-02-13
Publication date: 1981-08-19
Also published as: JPS56122655A; DE3005801C2; FR2475436A1; GB2068803B; BE887447A; DE3005801A1; FR2475436B1

Abstract

According to the present invention, accelerometers (3) are used to monitor the shock oscillations superimposed on the movement of the table and the friction forces between the casting and mould (2), and variations in the signals generated by the accelerometers (3) form a predetermined relationship used to indicate a disturbance in the casting process. Preferably at least three accelerometers (3) are used which are differentially connected, and the difference signals used to indicate such a disturbance. <IMAGE>

Description

SPECIFICATION Continuous casting processes This invention relates to continuous casting processes and particularly to a method and apparatus for monitoring such processes to obviate breakdowns or fracture of the casting.

The invention utilizes accelerometers located adjacent the mould path which monitors the passage of the casting.

From published German Application No: 2 743 579 a method is known for measuring and recording the variation of the acceleration of a continuous casting mould by means of one or more accelerometers arranged on the reciprocating or travelling table or on the mould itself. The variations actually measured are compared electronically with a given ideal curve, and the deviations therefrom used for controlling the continuous casting process.

These accelerometers are not suitable for use in the early detection of breakdown or fracture for the following reasons: 1. The method represented can detect only variations in the total forces at a mould.

2. The electronic filtering and the deviation from e.g. the ideal sinusoidal oscillation are based on the deviations filtered out from the sum of the oscillations.

3. Only the variations in the frictional forces of varying magnitudes are measured.

Early detection of fracture cannot be founded solely on the variation of the friction forces in a continuous casting mould. A fracture which develops in the mould varies the friction forces both in the positive and in the negative senses, so that it is not possible to obtain a clear indication from the variation of the total forces.

The present invention aims to provide a reliable method for the early detection and avoidance of fractures. To this end, the invention provides a method for obviating fractures in a continuous casting process wherein accelerometers on the travelling table monitor shock oscillations superimposed on the movement of the table and the friction forces between the casting and mould, and generate signals indicative thereof, variation of such signals from a predetermined relationship indicating a disturbance in the casting process.

The shock oscillations are determined by the movement of the lifting table and by the friction forces between casting and mould.

The invention also provides apparatus for monitoring a continuous casting process in a continuous casting installation, which apparatus comprises accelerometers arranged on at least one side of the mould of the installation for monitoring shock oscillations superimposed on the movement of the travelling table and the friction forces between the mould and a casting thereon, the accelerometers being connected to an evaluating unit for generating signals indicative of any variation of said forces from a predetermined relationship.

The method proposed by the present invention for the early detection of fractures is simpler and more reliable than the known art, since it expressly dispenses with measuring frictional oscillations or vibrations which are superimposed on the ideal sinusoidal pattern or other mould movement.

The invention is based on the realisation that a fracture at a slab casting normally begins with part of the casting crust or shell sticking to the mould wall in the vicinity of the narrow side, and at the height of the casting surface. The size of the shell which remains sliding decreases at each stroke, and therefore the amount of the total friction also.

At every downward stroke and every upward stroke there is brought about, usually unilaterally, a pushing-up movement and pullingdown movement respectively at the mould side on which the casting shell is sticking.

This deviation produced twice at each stroke in the case of slabs for example has an increasing tendency due to the one-sided growth of the suspended casting shell. The signal becomes greater in proportion as the asymmetry of the sticking casting shell is greater.

The invention will now be further described by way of example and with reference to the accompanying drawings in which: Figures 1 and 2 respectively show two embodiments of apparatus according to the invention.

As shown in Fig. 1, two accelerometers 3, which are typically piezoelectric quartz elements, are arranged on the broad side of a slab mould 1 for the continuous casting of steel, said mould having a mould frame 2.

The primary signals received from the accelerometers are fed to an electronic evaluating unit 4. When the mould is running idle it is possible by means of electronic compensating or adjusting elements at the individual measurement value pickups to arrange for the primary signals to be in unison, thus giving a difference signal of zero. This adjustment of the primary signals can also be effected during a normal casting operation.

If disturbances in the casting process occur in such a manner that differing friction conditions between casting shell and mould occur in the sense of an asymmetrical behaviour of the casting shell, a difference signal is produced since the primary signals are no longer coincident, but have even a divergent pattern over time.

By providing an indication of a negative or positive difference signal it is also possible to deduce the region of the mould (narrow side) in which there is a differing friction situation between casting shell and mould and, therefore, an undesirable non-uniform casting shell growth.

In the embodiment of Fig. 2 the basic outline is retained and the drawing layout is the same, but the mould is provided with three accelerometers. Two of the accelerometers 3 are situated at a broad side of the mould, whereas the third is arranged at the opposite broad side in the middle of the mould panel. The primary signals obtained from the accelerometers are here again fed to a unit for the evaluation of the signals. The evaluation is such that two signals in each case are evaluated with one another in the sense of obtaining normally a zero output.

With this arrangement the differential connection or circuit system, which may also be replaced by a quotient system, allows the region of the fault to be located more precisely as the casting shell solidifies in the mould. Thus a fracture can be prevented by planned per se known measures during the casting operation, and casting can continue. It will be appreciated that more than three accelerometers may be used if desired.

Claims

1. A method for obviating fractures in a continuous casting process wherein accelerometers on the travelling table monitor shock oscillations superimposed on the movement of the table and the friction forces between the casting and mould, and generate signals indicative thereof, variation of such signals from a predetermined relationship indicating a disturbance in the casting process.

2. A method according to Claim 1, wherein the accelerometers are differentially connected such that said signals are zero for all similar vibrations and oscillations of the casting, any difference signal generated by two accelerometers indicating a disturbance in the casting process.

3. A method according to Claim 1 or Claim 2 in which at least three accelerometers are used, located symmetrically on the mould.

4. A method according to Claim 3 in which two accelerometers are located symmetrically on one side of the mould, and a third is located centrally on the other side of the mould.

5. A method for obviating fractures in a continuous casting process substantially as described herein with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

6. Apparatus for monitoring a continuous casting process in a continuous casting installation, which apparatus comprises accelerometers arranged on at least one side of the mould of the installation for monitoring shock oscillations superimposed on the movement of the travelling table and the friction forces between the mould and a casting thereon, the accelerometers being connected to an evaluating unit for generating signals indicative of any variation of said forces from a predetermined relationship.

7. A method according to Claim 6 wherein the accelerometers are differentially connected, the evaluating unit generating signals indicative of the difference between friction forces monitored by the accelerometers.

8. A method according to Claim 6 or Claim 7 including at least three accelerometers arranged symmetrically on the mould.

9. A method according to Claim 8 having two accelerometers arranged symmetrically on one side of the mould, and a third centrally on the other side.

1 0. Apparatus for monitoring a continuous casting process substantially as described herein with reference to Fig. 1 or Fig. 2 of the accompanying drawings.