EP0356552B1 - Process for controlling sliding gate valves, particularly in continuous-casting machines - Google Patents

Description

The invention relates to a method for controlling slide closures, in particular a three-plate slide closure, the slide plate of which, controlled automatically by a processor in a throttle position, regulates the fill level of the melt of a mold and which, when the fill level control is paused, also has an automatically controlled opening stroke in a flow channel the throttle position opposite the slide closure performs an edge change of the standard edge.

With such edge changes, a shift in the control work from one edge of the flow bore of the slide plate to the opposite edge is brought about in practical casting operation, mainly in rotary slide closures, and thus uniform wear of the plate material is achieved. In contrast, for slide closures used in continuous casting plants, keeping the flow channel free of solid deposits is a priority. According to DE-A-3 742 215 (EP-A-0 320 575), which has not been published beforehand, this is done with an opening stroke of the slide plate out of the regulating throttle position, preferably into an opposite one, commanded by the processor of the fill level control while switching off this control Throttle position reached, with the additional advantage of even wear of the slide plate flow bore.

In the application of edge changes, problems arise especially with slide closures used to regulate the inflow of melts in continuous casting molds, on the one hand due to the melt inflow which is currently increased when changing the edges, and on the other hand because the throttle position assumed by the slide plate when the fill level control is released in the most cases does not do justice to the current level of the bath level in the mold.

As a result, considerable fluctuations in the level of the bath often occur, which in particular make the transition to the level control switched off during the edge change difficult and can considerably disrupt the casting operation.

The object of the present invention is to improve the transition to the fill level control with a system-inherent design of the edge change, or to increase bath level fluctuations occurring in the mold on an operating or. to maintain a quality-assured level.

The object is achieved according to the invention in that at least the throttle position to be picked up by the slide plate after an edge change is instructed by a sequence control of the edge change pre-programmed with the processor of the fill level control or assigned to the processor as a subroutine. In this way, edge changes can be easily arranged in a normal casting operation with level control or switched on during the casting instead of the level control without having to fear, for example, operational disturbances in the bath level fluctuations in the mold. Rather, an operationally reliable sequence of edge changes is guaranteed in any case, thus creating the basis for the planned use of the edge changes for different casting processes. Depending on the prevailing casting conditions, edge changes, regular or irregular, can be used to flush the flow opening of the slide closure or to optimize the wear of the slide plate or both, so that for each casting operation a specially created control procedure for slide closures with edge change control and level control is possible.

In detail, the invention proceeds in such a way that the sequence control measures one or more throttle positions in front of each edge change and the throttle position to be taken after the edge change is determined therefrom.

With simple mold cross sections, this simple method preferably keeps the bath level fluctuations that occur when alternating use of edge changes in fill level controls within required limits, especially when the throttle position to be taken after an edge change represents an average of at least two previously determined throttle positions.

For molds with medium or smaller cross-sectional sizes, the invention recommends that an edge change is initiated and / or ended by a reinforced throttling preprogrammed in the sequence control, which is designed as a stroke extension held over a period of time. As a result, the level of the bath level can be lowered both before and after the edge change in order to optimally compensate for the additional melt quantities that occur during an edge change. The values of the reinforced throttling should expediently be less than 10 mm for the hub additions and less than 10 seconds for the time spans, it being advantageous to choose values of the throttling reinforced on the input side greater than the values of the throttling reinforced at the end.

Figur 1

in schematischer Darstellung eine mit einem Schieberverschluss ausgerüstete Stranggiessanlage mit prinzipiellem Blockschaltbild der Füllstandsregelung,

Figur 2

die Auf-Position des Schieberverschlusses in grösserem Massstab,

Figur 3 und 4

Drosselstellungen des Schieberverschlusses in ähnlichem Massstab wie in Figur 2,

Figur 5 bis 7

Steuerkennlinien dreier verschiedener Steuerverfahren des Schieberverschlusses und

Figur 8

eine zur Steuerkennlinie nach Figur 6 gehörende Füllstandskennlinie.

Several exemplary embodiments of the invention are explained below with reference to the drawing. Show it

Figure 1

a schematic representation of a continuous casting installation equipped with a slide closure with a basic block diagram of the level control,

Figure 2

the open position of the slide closure on a larger scale,

Figures 3 and 4

Throttle positions of the slide closure on a similar scale as in Figure 2,

Figure 5 to 7

Control characteristics of three different control methods of the slide lock and

Figure 8

a level characteristic belonging to the control characteristic according to FIG. 6.

In FIG. 1, 1 means an intermediate vessel containing metallic melt with a slide closure 3 arranged on the spout 2. This has a fixed inlet plate 4, an adjustable slide plate 5 and a stationary outlet plate 6, the flow bores of which form a flow channel 7, the cross section of which is adjusted by adjusting the slide plate 5 can be changed in order to regulate the amount of melt that flows from the vessel 1 through a pouring pipe 8 connected to the outlet plate 6 to the mold 9. An actuator 10 is used to adjust the slide plate 5, the respective operating position of which is identified by a position meter 11. The mold 9 has a fill level 14 set for normal casting operation, monitored by a transmitter 12 (radiator) and a receiver 13. In it, the melt solidifies into a strand 15, which is drawn off by the drive rollers 16 of a take-off drive 17, the one is associated with a take-off speed meter 18 controller 19 coupled with control technology.

In terms of circuitry, the trigger speed meter 18 simultaneously sends its data to a control processor 20, which also receives and processes the data from the position meter 11 and the measured value receiver 13. The resulting control commands are sent by the processor 20 to the actuator 10 of the slide closure 3 and to the trigger controller 19.

The withdrawal speed of the strand 15 during normal casting operation is constant, which means that the desired fill level 14 of the mold 9 is regulated solely on the inflow side by means of the slide closure 3. For this purpose, the slide plate 5 assumes, for example, a throttle position D1, the control movements with the throttle edge K1 in the opening and closing directions allowed to maintain the equilibrium between the amount of melt flowing in per unit time and the strand 15 emerging from the mold 9.

Furthermore, so-called "edge changes" of the slide plate 5, which are particularly evident from FIGS. 3 and 4, are programmed in the processor 20 with the aid of a subroutine. That means from time to time after switching off the program control of the fill level 14 by means of the subroutine instead of the throttle edge K1, the throttle edge K2 is brought into the regulating throttle position D2 and the fill level control is then switched on again. The throttle characteristic curve according to FIG. 5 shows such edge changes that can be defined periodically. First, however, at the start of casting, the throttle edge K1 reaches the throttle position D1 defined in the processor when the slide plate 5 is extended with the stroke H1 from the open position A shown in FIG. 5 as a horizontal line (see also FIG. 2). There, the control of the fill level 14, which is shown on both sides of the up position A, which also functions as the time axis t, is automatically switched on. The straight-line edge changes 23 take place between the sections 22. With each of the changes 23 (H1 + H2), the slide plate 5 executes an opening stroke with the full opening of the flow channel 7, so that as a result of the currently changing flow of melt into the mold 9, the throttle position to be assumed, for example D2, is corrected with respect to the starting throttle position , for example D1. This correction is conveyed to the actuator 10 of the slide closure 3 by the processor 20, which receives and stores a value about the current position of the actuator 10 immediately before an edge change after switching off the level control 22, then from the last two values M1, for example and M2 determines an average value M3, which is the control command for the new throttle position D1 to be assumed (FIG. 5).

The control method of the slide closure 3 just described during an edge change of the slide plate 5 undergoes a training in accordance with FIG. This is done by means of a hub extension HX stored in the processor 20, which acts over the time tx and lowers the bath level in the mold 9 in order to compensate for the additional inflow of melt into the mold 9 that is to be expected during an edge change.

The method according to FIG. 7 also serves to compensate for the additional quantity of melt which arises as a result of an edge change. In addition to the increased throttling HX, tx, this also contains a further reinforced throttling HY, ty, but of a smaller format, at the end of each edge change before the release the level control provided. The reinforced throttling Hy, ty at the end serves the purpose of a forced level adjustment in order to bring the melt level to the desired fill level 14 as quickly as possible, in whose sections 22 according to FIG. 8 the edge changes 23 with the throttle reinforcements HX, tx, HY, ty according to FIG. 7 are automatically inserted .

The number of edge changes and their control variants according to the exemplary embodiments according to FIG. 5, FIG. 6 as well as FIGS. 7 and 8 are to be adapted to the respective slide closures 3 or the casting conditions of a continuous casting installation, whereby it can generally be assumed that more precise control processes (for example FIG. 7) for smaller mold cross sections and 8) apply.

Claims (6)

1. Method of controlling sliding gate valves, particularly a three-plate sliding gate valve, whose sliding plate, which is automatically controlled into a throttled position by means of a processor, controls the filling level of the melt in a mould and which in addition, with an intermittently connected filling level control, performs an edge reversal of the control edge into an opposite throttled position on the flow passage of the sliding gate valve with an automatically controlled opening stroke, characterised in that at least the throttled position (D1 or D2) to be adopted after an edge reversal (23) by the sliding plate (5) is instructed by a sequence control for the edge reversal (23) programmed with the processor (20) for the filling level control.
2. Method as claimed in claim 1, characterised in that before each edge reversal (23) the sequence control measures one or more preceding throttled position (D1 and D2) and determines therefrom the throttled position (D1 or D2) to be adopted after the edge reversal (23).
3. Method as claimed in claim 2, characterised in that the throttled position (D1 or D2) to be adopted after an edge reversal (23) is an average value (M3) of at least two previously determined throttled positions (M1 and M2).
4. Method as claimed in claims 1 to 3, characterised in that the edge reversal (23) is initiated and/or terminated by a preprogrammed increased throttling with an additional stroke (HX) and/or (HY) maintained over a time period (tx) and/or (ty).
5. Method as claimed in claim 4, characterised in that at the increased throttlings (HX,tx and HY,ty) the values for the additional strokes (HX and HY) are less than 10mm and the values for the time periods (tx and ty) are less than 10 seconds.
6. Method as claimed in claim 4 and 5, characterised in that the values of the initial increased throttling (HX,tx) are maintained larger than the values at the end (HY,ty).

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