EP0992302B1 - Method and apparatus for continuously controlling the basic setting and oscillation parameters of a continuous casting mould - Google Patents

Abstract

Process for continuously controlling the base adjustment and oscillating parameters of a continuous casting mold arranged in an elevating platform (10) comprises operating the platform using four corner, preferably double-acting hydraulic cylinders (2-5) in oscillations, and measuring the oscillating forces acting on the hydraulic cylinders during a casting pause or during the casting operation. An Independent claim is also included for an apparatus for carrying out the process comprising hydraulic cylinders (2-5) each having a piston (9) between two chambers (7, 8) with a hydraulic valve (13) controlling the pressure chambers. A pressure differential calculator (14) determines the effective resulting force of the hydraulic cylinder. A position transmitter (15) is connected to the cylinder.

Description

The invention relates to a method and a device for the continuous control of the Basic setting and oscillation parameters of a continuous casting mold arranged in a lifting table.

In continuous casting production, especially that under the term CSP (Compact Strip Production) known casting process for the production of thin slabs, the steel is introduced in a known manner from a ladle over shadow pipe, intermediate container and dip tube into the mold. This is in the upper area for receiving the dip tube funnel-shaped and designed for low-tension solidification of the strand skin. For comparatively high casting speeds, a lubricating film is used special casting powder between the walls of the mold and the strand solidifying used. This and the use of a high-frequency oscillation system in Combined with an optimal mold geometry, optimal strip surfaces can be achieved.

Chill mold oscillation is an essential part of the continuous casting process of Meta I-len. It enables the required lubricating effect of the lubricant, for example casting powder or oil, and thus reduces the coefficient of friction or the sticking of a strand on the mold walls. This has resulted from the melting of casting powder Slag has proven particularly useful as a lubricant in the mold, taking care that the mold powder permanently covers the bathroom mirror.

In the prior art, the simple solution to generating oscillation is motorized Eccentric drives generating a sinusoidal vibration form of the mold Frequency and amplitude are determined by the speed of the motor drive.

So that slag as a lubricant continuously in the gap between the cast strand and the mold wall it is common to set the amplitude and frequency of the mold in such a way that it periodically overtakes the strand as it moves down. This mode of operation is called a negative strip. This corresponds to each period of vibration the so-called healing time, during which the lubricant enters the gap between the strand shell and mold wall can penetrate.

It is also known that the essential oscillation parameters (negative strip, healing time, Amplitude and frequency of the mold oscillation and their combination) in every operating case must be set specifically for the quality of the cast product. The free Selection of the oscillation parameters is therefore an essential component for optimization of the continuous casting process and consists essentially in the choice of an optimal combination of amplitude and frequency, with the negative strip within specified limits should be, preferably between 15 and 40%.

However, an optimal combination of amplitude and frequency is sinusoidal Vibration of the mold hardly adjustable. As a result, methods and devices have already been developed known with the aim of determining the oscillation parameters of mechanical generating means to decouple in order to be able to influence the processes in the continuous casting mold in a targeted manner.

DE 37 04 793 C2 describes a device with two on a lifting table for the continuous casting mold or directly on this articulated eccentric shaft. In the connection between Rotary drive and the eccentric shafts, at least one cardan shaft is used, of which The rod end facing away from the eccentric shaft is arranged such that it can be changed in position, and the rod ends are rotatable against each other. This can be a non-sinusoidal movement due to a deliberately generated gimbal failure that occurs when a propeller shaft is not used in alignment between the waves. By changing height and lateral displacement of the rotary drive are different non-sinusoidal Movements of the mold can be realized.

EP 0 121 622 B1 describes a process for continuous casting using a Mold mounted in a frame, which is powered by two electro-hydraulic drive units is vibrated. The device is preferably operated at a frequency which is higher than the natural frequency of the vibration device.

An essential feature of the known sinusoidal and non-sinusoidal speed profiles is that the mold at a predetermined vibration frequency and Amplitude in each period, the time between two successive overtaking maneuvers of the strand through the mold corresponds to its downward movement Has speed and path course.

Casting speeds are required for the thin slab process with slab thicknesses of less than 100 mm of more than 4 m / min usual. The stroke frequencies are correspondingly high the mold, with which the usual values of the negative strip are achieved, namely about 400 up to 450 strokes / min, or approx. 7.5 Hz. At these high frequencies there are deviations of Vibration curve from the sinusoidal shape due to the small time intervals of approximately 0.13 up to 0.15 seconds / vibration can hardly be determined and have a lubricating behavior and the shell formation in the mold has hardly any influence.

Proceeding from this, the invention is based on the object using the oscillation technique one arranged in a lifting table and above this of four angular, double acting independent hydraulic cylinders in vibration-driven continuous casting mold to determine the actually existing oscillation forces with high accuracy and the detection of the actually acting forces for the machine and Use process control directly.

To solve the problem set in a method in the preamble of claim 1 mentioned type with the invention proposed that the lifting table of the continuous casting mold of four angular, preferably double-acting hydraulic cylinders in Vibrations is driven and those actually acting on the hydraulic cylinders Oscillation forces during casting break and / or casting operation are measured and diagnosed the casting machine and / or the casting process.

The vibration drive by means of four hydraulic cylinders that can be driven independently of each other gives almost unlimited variation possibilities for the resulting mold vibration formation.

a) die effektiv wirkenden Kräfte der Oszillationsbeschleunigung und

b) die diesen zugeordneten Positionen der Kolben der Hydraulikzylinder ermittelt und aus diesen zeitzyklisch ermittelten Meßdaten,

c) der Massenschwerpunkt des schwingenden Systems;

d) die Reibungskräfte zwischen Kokillenwänden und Strangschale,

e) die Einstellung der Kokille relativ zur Achse des Gießstranges,

f) die Nullinie der Kokillenschwingungen relativ zur Lage des Badspiegels,

g) das Verhältnis von Negativstrip der Kokille zur sogenannten Heilzeit, während welcher Schmiermittel zwischen Strangschale und Kokillenwände eindringt, errechnet werden.

In an embodiment of the invention it is provided that for each hydraulic cylinder

a) the effective forces of oscillation acceleration and

b) the positions of the pistons of the hydraulic cylinders assigned to these are determined and from these time-cyclically determined measurement data,

c) the center of mass of the vibrating system;

d) the frictional forces between the mold walls and the strand shell,

e) the setting of the mold relative to the axis of the casting strand,

f) the zero line of the mold vibrations relative to the position of the bath level,

g) the ratio of negative strip of the mold to the so-called healing time, during which lubricant penetrates between the strand shell and the mold walls, is calculated.

• Auswuchthilfe für die Grundeinstellung der Oszillation, insbesondere mittels Schwerpunktbestimmung des schwingenden Systems;
• Online-Darstellung der aktuellen Maschinenbelastung, insbesondere mittels Visualisierung der Meßdaten mit Hilfe eines Monitors;
• Verschleißüberwachungen von Federn, Zylinder sowie Wasserkompensatoren;
• Überlastsicherung beim Anfahrvorgang und während des kontinuierlichen Gießvorgages;
• Schmierungsüberwachungen bzw. Gießpulverzuführung, sowie Erfassung von Schwerpunktsänderungen im Gießbetrieb infolge Mangelschmierung bzw. Krafterhöhung;
• Verschleißüberwachung von Federn, Zylindern und Wasserkompensatoren;
• Automatische Abgleichmöglichkeiten zur Schwerpunktsverschiebung bzw. Zentrierung mit der Zielsetzung eines ruhigen, senkrechten Bewegungsablaufs der Kokille.

The following measures are made possible with great advantage using the method according to the invention:

• Balancing aid for the basic setting of the oscillation, in particular by determining the center of gravity of the vibrating system;
• Online display of the current machine load, in particular by means of visualization of the measurement data using a monitor;
• Wear monitoring of springs, cylinders and water compensators;
• Overload protection during start-up and during the continuous casting process;
• Lubrication monitoring or casting powder supply, as well as detection of changes in the center of gravity in the casting operation due to insufficient lubrication or increase in force;
• Wear monitoring of springs, cylinders and water compensators;
• Automatic adjustment options for shifting the center of gravity or centering with the objective of a quiet, vertical movement of the mold.

An embodiment of the method provides that by means of those used for the oscillation drive corner hydraulic cylinder the actually occurring oscillation forces in a plane perpendicular to the casting strand is determined with an accuracy of approximately +/- 20 kg become.

Another embodiment of the method provides that the Machine and process data b) to d) the working pressures on both sides of the work surface of the cylinder and two depending on the position-dependent forces opposite cylinder chambers determines the effectively resulting force of each cylinder becomes.

Further refinements of the method according to the invention provide that from the measurement data the frictional forces between the mold and the strand are continuously determined and monitored and in accordance with a predeterminable friction force value, the lubricant supply to the The mold is checked or adjusted.

It is provided that the setting with the help of a selectable focus regulation a quiet, vertical movement of the mold or the casting strand becomes.

For a further embodiment of the invention it is provided that from the time-cyclically determined Measured data with cycle times between 1 and 10 m / s visualizable diagnostic diagrams the mold speed, the mold path (amplitude) and the strand withdrawal speed be made visible in a monitor and thus be visually monitored.

The measure has a particularly advantageous effect on the method that as a result Decoupling the mold and its oscillation parameters from forced operation one empirical optimal adjustment of the vibration level to the withdrawal direction of the casting strand is set.

A further embodiment of the method provides that at an arbitrarily specified strand withdrawal speed the zero line of the mold vibrations relative to the position of the bath mirror during the casting process in accordance with the casting parameters, in particular the Casting speed is shifted up or down.

• daß dem Hydraulikzylinder ein die Leitungen für Druckmedium zu und von den Druckkammern des Zylinders kontrollierendes Hydraulikventil vorgeschaltet und diesem ein Differenzdruckrechner zur Ermittlung der effektiv resultierenden Kraft des Hydraulikzylinders nebengeordnet ist, daß dem Hydraulikzylinder ein Positionsgeber zugeordnet ist, und daß die vom Rechner und dem Positionsgeber ausgehenden Signalleitungen einer den Hydraulikzylindern zentral zugeordneten Recheneinheit aufgeschaltet sind, die über Kommandoleitungen die Steuerung aller erforderlichen Betriebsfunktionen überwacht.

A device for continuous control of the basic setting and oscillation parameters of a continuous casting mold arranged in a lifting table and driven by four angular hydraulic cylinders in vibration, each cylinder, as a double-acting hydraulic unit, having a working piston arranged between two pressure chambers, is distinguished by

• that the hydraulic cylinder is preceded by a hydraulic valve that controls the lines for pressure medium to and from the pressure chambers of the cylinder, and a differential pressure computer for determining the effectively resulting force of the hydraulic cylinder is arranged next to it, that a position transmitter is assigned to the hydraulic cylinder, and that those originating from the computer and the position transmitter Signal lines of a computing unit centrally assigned to the hydraulic cylinders are connected, which monitors the control of all necessary operating functions via command lines.

Figur 1

eine schematische Darstellung der Vorrichtung mit von vier eckständigen Hydraulikzylinder getragenem Hubtisch mit Kokille in Form eines Stammbaumes;

Figur 2

eine Draufsicht von Kokille und Hubtisch;

Figur 3

ein Kraft-Positions-Diagramm eines Oszillations-Zylinders.

Further details, features and advantages of the invention result from the following explanation of an exemplary embodiment shown schematically in the drawings. Show it:

Figure 1

a schematic representation of the device with four angular hydraulic cylinders carried lifting table with mold in the form of a family tree;

Figure 2

a plan view of the mold and lifting table;

Figure 3

a force-position diagram of an oscillation cylinder.

The oscillation device shown in the family tree in FIG. 1 comprises a rectangular one Lift table 10, which receives the mold 1 in a positive and non-positive manner. This lifting table 10 is Free swinging on four servo hydraulic cylinders 2 to 5 and is based on proven Type of laterally supported, horizontally arranged leaf springs (not shown) in guided its vertical direction of vibration.

Each hydraulic cylinder 2 to 5 has one between an upper pressure chamber 7 and one lower pressure chamber 8 movably arranged piston 9, the upper and lower working surface can be acted upon by the working medium of the upper or lower pressure chamber 7, 8 is. From the resulting difference in forces, the current effect results Force of a cylinder.

Each hydraulic cylinder 2 to 5 is a supply and discharge lines 11, 12 for pressure medium to and from the pressure chambers 7, 8 of the cylinder 2 to 5 controlling hydraulic valve 13 upstream and this a differential pressure calculator 14 to determine the effective resulting force of the hydraulic cylinder 2 to 5 is subordinate.

Furthermore, a position transmitter 15 is assigned to each hydraulic cylinder 2 to 5, from which by calculation in the centrally assigned arithmetic unit 18 from those with the signal lines 16, 17 input measured data calculated control signals and this via command lines 19 to control the required operating functions to the corresponding operational control devices are transmitted.

The pressures of the individual pressure chambers 7, 8 of a cylinder 2 to 5 are determined by signal lines 11, 12 connected to the hydraulic valve 13, which in turn with the pressure pump 20 for the operating medium is connected.

FIG. 2 shows a top view of the lifting table 10 with the arrangement of the lifting table and in Vibrating hydraulic cylinders 2 to 5. The continuous casting mold 1 is approximately installed in the central area of the lifting table 10.

With S1 or S2, possible centers of gravity are the sum of the oscillating forces of the individual Hydraulic cylinders 2 to 5 marked. The focus S1 is, for example, at approximately equilibrium of forces of the four hydraulic cylinders 2 to 5. In contrast, the Center of gravity S2 to the bottom right if the force of cylinder 2 is greater than that of remaining oscillation cylinder. In this way, an oscillation on the mechanical Zero point S1 via the force setting of the individual oscillation cylinders with extreme accuracy can be set.

Finally, FIG. 3 shows a force / displacement diagram of an acceleration cycle using the example of a hydraulic cylinder. The X axis shows the effective force of the oscillation acceleration depending on the position b) of the piston assigned to this in the hydraulic cylinder. The relationship is from the steepness of the diagram according to the angle α of force and position can be determined exactly, which is a possibility in practice Function monitoring, for example, the frictional forces between the mold walls and the strand shell or to detect irregularities, for example, breakage of one of the guide springs or a compensator or damage to a cylinder. It can be done by Determining the value F when reversing the direction of a hydraulic cylinder, for example a broken spring recognize quickly.

For the first time, the invention enables precise monitoring at high oscillation frequencies the decisive operational functions of the casting machine and casting process.

Claims (10)

1. Method for continuously checking the basic setting and oscillation parameters of a continuous casting chill mould arranged in a lifting table (10), characterised in that the lifting table (10) of the continuous casting chill mould (1) is driven to perform oscillations by four corner, preferably double-acting, hydraulic cylinders (2 to 5) and the oscillation forces actually acting on the hydraulic cylinders are detected in terms of measuring technology in casting pause and/or casting operation and are used for diagnosis of the casting machine and/or of the casting process.
2. Method according to claim 1, characterised in that

   a) the effectively acting forces of the oscillation acceleration and

   b) the positions associated therewith of the pistons of the hydraulic cylinders are ascertained for each hydraulic cylinder (2 to 5) and from these measurement data cyclically ascertained over time there are calculated

   c) the centre of mass of the oscillatory system,

   d) the friction forces between chill mould walls and strand skin,

   e) the setting of the chill mould (1) relative to the axis of the cast strand,

   f) the neutral axis of the chill mould oscillations relative to the position of the bath level and

   g) the ratio of negative strip of the chill mould relative to the so-called curing time, during which lubricant penetrates between strand skin and chill mould walls.
3. Method according to claim 1 or 2, characterised in that the actually occurring oscillation forces are ascertained in a plane, which is perpendicular to the cast strand, with an accuracy of approximately ± 20 kg by means of the corner hydraulic cylinders (2 to 5) used for the oscillation drive.
4. Method according to claim 1, 2 or 3, characterised in that the operating pressures at both sides of the work surface of each hydraulic cylinder (2 to 5) are used as basis of the calculation of the machine and process data c) to g) and the effective resultant force of each cylinder (2 to 5) is determined from the position-dependent associated forces of each two oppositely directed cylinder chambers.
5. Method according to one or more of claims 1 to 4, characterised in that the friction forces between chill mould and strand are continuously determined and monitored from the measurement data and the lubricant feed to the chill mould is controlled and/or set in dependence on a predeterminable friction force value.
6. Method according to one or more of claims 1 to 5, characterised in that the setting of a steady vertical course of movement of the chill mould or of the cast strip is undertaken with the help of a selectable centre-of-gravity regulation.
7. Method according to one or more of claims 1 to 6, characterised in that diagnostic diagrams, which can be visualised, of the chill mould speed, the chill mould travel (amplitude) and the strand withdrawal speed are made visible in a monitor at cycle times between 1 and 10 ms from the measurement data cyclically ascertained over time and thus made capable of being optically monitored.
8. Method according to one or more of claims 1 to 7, characterised in that an optimum adaptation of the oscillation plane to the withdrawal direction of the cast strand is empirically set in consequence of decoupling the chill mould and the oscillation parameters thereof from constrained guides.
9. Method according to one or more of claims 1 to 8, characterised in that in the case of any predetermined strand withdrawal speed the neutral axis of the chill mould oscillations is displaced upwardly or downwardly relative to the position of the bath level during the casting process in dependence on the casting parameters, particularly the pouring speed.
10. Device for continuous checking of the basic setting and oscillation parameters of a continuous casting chill mould (10) arranged in a lifting table (10) and drivable by way of this by four corner hydraulic cylinders (2 to 5) to perform oscillations, wherein each cylinder has, as a double-acting hydraulic unit, a working piston (9) arranged between two pressure chambers (7, 8), and a hydraulic valve (13) controlling the ducts (11, 12) for pressure medium to and from the pressure chambers (7, 8) of the cylinder is arranged upstream of each hydraulic cylinder (2 to 5) and a differential pressure calculating means (14) for determining the effective resultant force of the hydraulic cylinder (2 to 5) is coordinated with the hydraulic valve and wherein a position transmitter (15) is associated with the hydraulic cylinder (2 to 5), and the signal lines (16, 17) from the calculating means (14) and the position transmitter (15) are connected to a computing unit (18), which is centrally associated with the hydraulic cylinders (2 to 5) and which monitors the control of all necessary operating functions by way of command lines (19).

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