AT519154B1 - Regulation of the narrow side taper of a continuous casting mold - Google Patents

Abstract

The invention relates to a method and a device for regulating the narrow side taper of a continuous casting mold based on the measurement of the forces applied to the narrow sides with the aid of actuators. In order to achieve the best possible narrow-side taper, in which the temperature-related shrinkage is compensated for as precisely as possible by the positioning of the narrow-side plates on the cast metal strand, and thus the largest possible contact with the metal strand is produced, the invention proposes a control circuit whose control deviation is based on the measurement of the forces occurring on the actuators during continuous casting. By means of suitable parameterization of the controlled variable, the regulation and filtering the control loop, a very fast and reliable control behavior can be realized. Double-acting hydraulic cylinders are proposed as actuators for a device according to the invention.

Description

CONTROL OF THE NARROW-SIDED CONICITY OF A CONTINUOUS CHOCOLATE The invention relates to a method for controlling the narrow-side taper of a continuous-casting mold based on the measurement of the forces applied to the narrow sides.

Furthermore, the invention relates to a continuous casting mold, the narrow side plates of which are employed with the aid of actuators located at different distances from the pouring side in accordance with the method according to the invention.

Continuous casting molds are used in the casting of metal slabs, in particular in the casting of steel slabs. In this case, a continuous casting mold, in which the method according to the invention is used, consists of four individual metal plates, the so-called mold plates, which are arranged so as to be displaceable relative to one another and are preferably made from a copper alloy and essentially have a cuboid shape.

With respect to the casting direction of the continuous casting mold, all four mold plates have approximately the same extent, which is consequently referred to as mold height H. In addition, two of the mold plates each have the same dimension in the width direction. The mold plates of the pair with the larger dimension in the width direction are also referred to as broad side plates, those with the smaller dimension in the width direction as narrow side plates.

The four mold plates of a continuous casting mold are arranged at the same height with respect to the casting direction, the two broad side plate plates and the two narrow side plates each lying opposite one another. This creates a mold open on both sides, the openings of which are referred to as the pour-side or outlet-side end and which have a rectangular cross section with respect to a cutting plane normal to the casting direction.

The arrangement of the mold plates to one another is such that each of the two broad side plates contacts the two narrow side plates with their inner surface during the casting process, and vice versa, each narrow side plate with two opposite outer surfaces contacts the two broad side plates. The distance between the outlet-side ends of the narrow side plates is referred to as the casting width, since this distance defines the dimension of the cast metal strand when it emerges from the mold.

On the one hand, this arrangement enables the narrow side plates to be moved parallel to the inner surfaces of the broad side plates even during the casting process. On the other hand, a clamping force can be exerted on the narrow side plates by mechanically positioning the wide side plates against the narrow side plates.

The - based on the direction of casting - enclosed by the mold plates is referred to below as the interior of the mold, accordingly the interior facing surfaces of the mold plates are referred to as their inner surfaces, analogously, the inner surfaces of the respective cuboid mold plates are opposite surfaces also referred to as the outer surfaces of the mold plates.

On the outer surfaces of the mold plates, so-called back-up plates are generally attached, which, on the one hand, ensure adequate mechanical stability of the mold plates and, on the other hand, contain a cooling device which dissipates the heat of the molten metal released during continuous casting from the mold plates. Such devices, e.g. Milling on the outer surfaces of the mold plates, which together with the backing plates form cooling channels through which water flows, are well known from the prior art.

The displaceable arrangement of the mold plates to each other is carried out by appropriate actuators, which make it possible to position individual mold plates spatially and thereby

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AT 519 154 B1 2019-12-15 Austrian patent office to vary the cross-sectional area of the mold that is decisive for the dimension of the metal slab produced. Such actuators can e.g. be motor-driven spindles or hydraulic actuators, which are also known from the prior art.

During the casting process, a molten metal is introduced into the interior of the mold at the end on the pouring side, the molten metal starting to solidify in the contact area with the mold plates because of the heat given off to the mold plates, and a so-called strand shell is formed in this region, the thickness of which increases as it passes of the corresponding strand section through the mold continuously increased. The metal strand which is partially solidified in this way is pulled out by appropriate pull-out devices, e.g. driven driver rollers in the roller table following the mold, pulled out of the mold at the outlet end thereof, this process being supported by mechanical oscillation movements of the mold itself.

The surface of the molten metal in the interior of the continuous casting mold is also referred to as a mold level. Accordingly, the so-called mold level height h is defined as the distance of the mold level from the exit end of the mold.

Furthermore, casting powder is applied to the molten metal at the pouring-in end of the mold, which is melted on the surface of the still molten metal melt by the heat given off and subsequently forms a sliding film between the strand shell that forms and the inner surfaces of the mold plates, which reduces the mechanical friction between the strand shell and the inside of the mold plates.

Despite the formation of a strand shell, the majority of the section of the metal strand located inside the mold remains in the liquid phase. A corresponding ferrostatic pressure therefore acts on the strand shell, which must be compensated for by a corresponding counterpressure of the mold plates, since the strand shell itself cannot build up sufficient counterpressure.

For this reason, a corresponding pressure force is applied during the casting process, in particular on the narrow side plates by means of their actuators, since the clamping effect which the broad side plates exert on the narrow side plates is generally not sufficient.

An actuator arranged on a narrow side plate has a point of application at which a force is transmitted to the narrow side plate and the narrow side plate is moved at this point by a spatial displacement of the point of application by the actuator. This point of attack can be designed to be articulated if, for example, the inclination of the narrow side plate changes during the displacement by the actuator. In this sense, the point of attack is assigned a position which is displaceable in space and which is referred to below as the actuator position. Furthermore, an actuator comprises a sensor with which the current value of the actuator position is recorded, which is also referred to as the actual position of the actuator and which is transmitted to a control unit.

In the case of position control of the actuator, the control unit specifies a specific position value, which is also referred to below as the target position of the actuator. The actual position of the actuator is compared with its target position and the actuator is controlled by the control unit such that the actual position and target position match. This actuation takes place by applying an appropriate mechanical force to the actuator, which is transmitted to the narrow side plate via the point of application of the actuator and as a result of which the position of the narrow side plate is changed at this point. A mechanical force is also applied to the actuator by the control unit and can take place, for example, by changing the hydraulic pressure if the actuator is designed in the form of a hydraulic cylinder.

[0018] During the casting process, all actuators of the continuous casting mold are given individual target positions and thereby the inward forces of the individual actuators

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AT 519 154 B1 2019-12-15 Austrian patent office regulated in such a way that the interaction of all actuators during the casting process - with the exception of the process of adjusting the position of the narrow side plates - exactly balances the outward forces of the molten metal, as otherwise the narrow side plates will balance out would move. There is therefore a balance of forces between the outward forces caused by the ferrostatic pressure of the molten metal and the inward forces of the actuators.

Since metal alloys experience a reduction in their spatial volume during their solidification and subsequent cooling, the cast metal strand shrinks accordingly as it passes through the mold. It is also known that in order to achieve the highest possible quality, the cast metal strand should have as large a mechanical contact as possible with the inner surfaces of the mold plates when it passes through the mold. However, if the strand shell lifts off from the inner surface of the mold due to thermal shrinkage, this significantly reduces the heat flow from the metal strand at the point in question, which results in a non-uniform quality of the strand surface and, in extreme cases, can lead to the strand shell being torn open.

One measure to achieve the largest possible and even contact of the metal strand passing through the mold is to specify a slight inclination between the opposing mold plates, so that the cross section of the mold from the pouring end to the exit end corresponds to the Shrinkage of the metal strand tapers.

The inclination of the opposite broad side plates is usually achieved by a trapezoidal shape of the narrow side plates: since the narrow side plates contact the two broad side plates along their vertical extension, there is a different distance between the upper, pour-side ends of the two broad side plates than between the lower, exit-side ends of the broad side plates. The quotient of the difference between the upper distances f and the lower distances d between the broad side plates and the mold height H accordingly

K _b = (f - d) / h is also called broadside taper.

In a similar manner, the taper of the narrow side plates - hereinafter also referred to as narrow side taper K _s - is usually the difference between the distance e between the ends of the narrow side plates on the pouring side and the distance b between the ends of the narrow side plates on the outlet side, which is identical to the casting width b , according to

K _s = (e - b) / b defined. However, other definitions of the narrow side taper are also possible, it being essential that they depend on the inclination of at least one of the narrow side plates with respect to the casting direction. It is conceivable, for example, to refer to a definition for the narrow side taper only on a single narrow side plate

K _Si1 = (θτ - / E with 1 e {1,2}, the index 1 denoting the first and the second narrow side plate and θτ the inlet and outlet normal distance of the narrow side plate 1 to the geometric center line of the continuous casting mold. In the case of such a , only a definition of the narrow side taper relating to a narrow side plate is therefore assigned two values for the narrow side taper to the continuous casting mold.

Since the broadside cone is determined solely by the geometric shape of the narrow side plates, no influence can be exerted on it during the casting operation. In order to improve the contact of the inside of the mold with the strand shell during the casting process, solutions are known from the prior art which influence the shape of the narrow side plates of a mold.

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AT 519 154 B1 2019-12-15 Austrian Patent Office The formation of the strand shell when the metal strand passes through the continuous casting mold depends on various factors, such as the casting speed, the composition of the molten metal itself, the properties of the casting powder or the cooling capacity of the cooling device of the mold, which also influence the heat transfer from the cast metal strand to the mold and thus the mechanical contact of the metal strand with the mold.

From JP 2010 253548 A, a construction for continuous casting molds is known, which proposes to mechanically bend the narrow side plates during casting as a function of the casting speed, the carbon content of the molten metal or the heat flow passing from the metal strand to the mold, the Heat flow is calculated from temperature values of the cooling water of the cooling device of the mold. The aim of this invention is to keep both the solidification profile of the strand shell and the frictional forces that occur on the inner surfaces of the mold plates as constant as possible, even with changing casting conditions, by the targeted bending of the narrow side plates, and thus to avoid the formation of longitudinal cracks in the cast metal strand , A complex bending mechanism according to FIGS. 15 and 18 is used to apply the required bending forces.

JP H03 210953 A proposes a continuous casting mold, the narrow side plates of which each have a groove 15 extending in the horizontal direction perpendicular to the casting direction, which is why a kink corresponding to FIG. 1 forms at this point under the action of force. This action of force is regulated as a function of temperature values measured by means of a thermocouple in the vicinity of the outlet end of the narrow side plates. The grooves of the narrow side plates represent a mechanical weak point.

JP H02 247059 A proposes to bend the narrow side plates together with the backing plates mounted thereon depending on the measured heat flow or the casting speed. The bending forces required for this are very high, the inner surfaces of the narrow side plates assume a curve along the casting direction.

A disadvantage of all the publications mentioned above is that high mechanical forces or correspondingly complex trades are required to bend the narrow side plates.

In addition, a hypothetical solidification course of the strand shell is assumed in the publications mentioned, for which a physical modeling is necessary, which in turn depends on various influencing factors and is therefore subject to corresponding uncertainties, since no direct measurement of the actual contact area between strand shell and the inner surfaces the mold plate takes place.

Another disadvantage of the above-mentioned publications is that a control system which is based on a measured temperature value or a measured heat flow has a correspondingly inherent inertia and therefore cannot react quickly enough to rapidly changing production conditions.

In order to avoid disadvantageous mechanical loads on the narrow side plates, the present invention therefore proposes, instead of bending the narrow side plates to change their spatial position during the casting operation, by guiding them along the inner sides of the wide side plates. This is done by reducing the clamping force that the broad side plates exert on the narrow side plates, then adjusting the narrow side plates accordingly using appropriate position-controlled actuators and finally adjusting the contact pressure of the broad side plates to the original value. Such an adjustment process takes place in a controlled manner and in such a way that, despite the outward forces of the molten metal melt, there is no sudden tearing of the strand shell.

In particular, that of the narrow side taper to that of the formation of the

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AT 519 154 B1 2019-12-15 Austrian patent office

Strand shell resulting shrinkage of the metal strand are adjusted so that the contact area of the narrow side plates with the strand shell is as large as possible. No forces are applied for the bending of the narrow side plates themselves and the frictional forces between the strand shell and the inner surfaces of the mold plates are not unnecessarily increased.

With an optimal narrow side taper in this sense, the adjustment of the narrow sides of the mold corresponds exactly to the shrinkage of the strand, which is caused by the growth of the strand shell. Typical values of the narrow side taper are between 0.9% and 1.3% of the pouring width according to the above definition.

Excessive taper of the narrow side plates, which causes the strand to be crushed by the mold, causes increased wear on the surface of the mold and increases the friction between the mold and the strand. Under certain circumstances, when the metal strand passes through the continuous casting mold in the edge area where the narrow side plates and the broad side plates meet, the strand shell can also bulge inwards, which in turn leads to longitudinal defects in the metal strand.

On the other hand, a narrow side taper which is too low creates a gap between the strand shell and the narrow side plates of the mold, which can lead to reduced strand shell growth due to insufficient heat dissipation via the mold walls. A resulting bulging of the strand in the mold can, in addition to an increased probability of breakdown, also lead to quality problems in the edge region of the metal strand.

The optimal narrow side taper depends on various production parameters, such as the shrinkage characteristic of the cast metal melt or also from the actual heat dissipation, which is determined, among other things, by the properties of the mold powder and the casting speed. It therefore makes sense to dynamically adapt the narrow side taper to the prevailing casting conditions during casting.

The adjustment of the narrow side taper of a continuous casting mold during the casting operation depending on a production parameter is known from the prior art. In order to ensure rapid adjustment of the narrow side, the wide side plates can be permanently clamped, for example, by a preset spring clamp, the clamping action of which is only briefly opened by a corresponding unclamping device during the adjustment of the narrow side taper by actuators of the unclamping device canceling the clamping force of the spring clamp.

[0038] DE 10 2014 227 013 A1 describes the adjustment of the narrow side taper of a continuous casting mold as a function of a temperature distribution in the mold plates and the mechanical contact of the strand shell derived therefrom to the inner surfaces of the mold plates. The temperature distribution is preferably determined with the aid of optical waveguide sensors, with conclusions being drawn about the mechanical contact or the formation of air gaps from the ratio of measured values between centrally located and near-edge temperature sensors.

On the one hand, the temperature-based regulation of the narrow side cone described in DE 10 2014 227 013 A1 is relatively slow - for example, the lifting of the strand shell can only be detected with a corresponding time delay. On the other hand, this control method is based only on the heat flow from the cast metal strand to the mold plates and the associated temperature changes, but without taking into account frictional forces, and is therefore only an indirect method for determining the appropriate taper, which is subject to corresponding inaccuracies.

[0040] JP S56 119646 A describes a continuous casting mold, the plates of which are moved under pressure control during casting. The narrow side plates are each movably connected at their pour-side end to a base plate which can be moved and fixed in the horizontal direction. Near the end of the narrow side plate on the pouring outlet side

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AT 519 154 B1 2019-12-15 Austrian patent office is the point of application for a pressure-controlled actuator, e.g. a hydraulic cylinder that presses the narrow side plates against the cast metal strand, with a small gap distance of 0.1 - 0.2 mm in the casting direction between the narrow side plates and the wide side plates to enable their relative movement.

Although this invention allows a quick reaction to changing production conditions in relation to the contact of the narrow side plates with the metal strand because of the pressure-controlled actuation of the lower actuators, at the same time the movements of the actuators adjust the narrow side cone itself, so that the contact behavior of the narrow side plates on the one hand and the optimal value of the narrow side cone on the other hand cannot be set independently. In addition, a uniform pouring width cannot be maintained, since during a control process the narrow side plates are tilted at their lower end and, moreover, it cannot be guaranteed that the narrow side cone is identical on both sides, which can lead to non-uniform growth of the strand shell.

Furthermore, it is common to use known production parameters such as e.g. the composition of the molten metal, the casting width, the current casting speed or a heat flow calculated from measured temperature values, to calculate a value for the narrow side taper and to specify this value manually using the automation system of the relevant continuous casting plant. This procedure is based either on empirical values or a model assumption with regard to strand shell growth and is therefore subject to a corresponding number of uncertainties, and there is also no precise reproducibility due to the manual intervention.

It is therefore an object of the present invention to overcome the disadvantages of the aforementioned methods and to disclose a method for regulating the narrow-side taper of a continuous casting mold which, depending on the current process conditions, allows the optimum value of the narrow-side taper to be set as quickly and reproducibly as possible The largest possible contact area between the strand shell and the inside of the mold allows without unnecessarily increasing the frictional forces.

[0044] The object is achieved according to the invention by the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

In the following, a continuous casting mold is assumed, the narrow side plates of which can be moved along at least two mechanical actuators along the inner sides of the broad side plates, and as a result of which an inward force is exerted on the continuous shell of the cast metal strand in order to counteract the outwardly acting ferrostatic pressure to counteract the not yet solidified metal melt, since the clamping effect of the narrow side plates by the broad side plates and the intrinsic cohesive force of the strand shell itself are not sufficient to prevent the strand from tearing open. These forces transmitted from the narrow side plates to the strand shell are referred to below as narrow side forces.

It is assumed that the casting direction of the continuous casting mold 1 is oriented essentially in the direction of the acceleration due to gravity; Therefore, the ferrostatic pressure of the molten metal introduced into the mold 1 increases linearly in the casting direction in accordance with the behavior of a liquid with the distance to the surface of the molten metal which is located in the casting direction at a distance corresponding to the level of the mold level above the outlet ends of the mold plates.

The increase in pressure within the liquid metal melt naturally continues below the outlet end of the continuous casting mold. A good approximation of a deviation from the linear rise due to the temperature dependence of the density of the molten metal can be neglected, since the temperature of the melt introduced into the mold is only slightly above the solidification temperature.

The ferrostatic pressure of the molten metal causes outward forces that

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AT 519 154 B1 2019-12-15 Austrian patent office must be compensated by corresponding inward counter forces to prevent the strand shell from tearing.

When the molten metal passes through the continuous casting mold, the cooling effect leads to the formation of a strand shell along the inner surfaces of the mold plates. The strand shell has an inherent strength which depends locally on its thickness and which partially compensates for the ferrostatic pressure of the molten metal which acts on the outside. The remaining part of the ferrostatic pressure inside the continuous casting mold must be compensated for by appropriate counterpressure of the mold plates in order to avoid tearing of the strand shell.

While the corresponding back pressure is automatically set by the fixed clamping of the broad side plates, the back pressure along the narrow side plates must be actively regulated, since there is no complete clamping effect of the narrow side plates through the broad side plates. The spatial position and orientation of the narrow side plates is therefore carried out by active position control of the mechanical actuators moving the narrow side plates.

After the metal strand emerges from the continuous casting mold, the strand shell has already grown to such an extent that the ferrostatic pressure which exceeds the inherent strength of the strand shell can be easily compensated for by spatially fixed or position-controlled strand guide rollers, the strand guide rollers directly supporting the surface of the extended metal strand ,

Experiments show that the narrow side forces with decreasing casting speed (less than 0.6 meters per minute) always decrease due to the formation of the strand shell and the associated strand shrinkage, until the metal strand at very low casting speeds (0 to 0.2 meters per minute) almost completely loses contact with the mold narrow sides and the narrow side forces tend towards zero.

Tests also show that an adjustment of the narrow side taper has a direct influence on the required narrow side forces.

There is therefore an empirical relationship between the narrow side forces and the casting speed. There is also a connection between the narrow side forces and the narrow side taper.

The present invention for setting the optimal possible value of the narrow side taper, in which the inclination of the narrow side plates against the forming shell shell exactly compensates for the shrinkage of the metal strand, is based on the use of this relationship and proposes a method for setting a narrow side taper K _s one Continuous casting mold for the production of a metal strand with the help of at least one control circuit, the continuous casting mold comprising a first and a second narrow side plate, on each of which at least two position-controlled actuators for positioning the respective narrow side plate are arranged at different distances from the end of the continuous casting mold on the pouring side and in the direction of action corresponding forces occur during operation of the continuous casting mold, characterized in that during a cycle run through the at least one control loop

a reference pressure P _ref as a reference variable and

an average surface pressure P _med between the narrow side plates and the metal strand as a control variable, the average surface pressure P _{med being determined} from the forces occurring in the direction of action of the actuators, and that

- A controller as a function of a control deviation P _dif = P _ref - P _med as the input variable determines the narrow side taper K _s as the manipulated variable of the control loop and that

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- The position of the first and / or the second narrow side plate is set according to the narrow side taper K _s over a controlled system by means of the actuators.

According to the invention, each of the two narrow side plates of the continuous casting mold can be positioned by a separate, independent control circuit which only controls the actuators of the respective narrow side plate. In this case, the manipulated variable of the control loop in question depends on the inclination of the respective narrow side plate with respect to the casting direction and the method according to the invention thus comprises two independent values for the narrow side conicity - in each case one value for the first and one value for the second narrow side plate - the continuous casting mold ,

Alternatively, however, a common control circuit can be used for both narrow side plates, which accordingly controls the actuators of both narrow side plates. In this case, the method according to the invention comprises a common value for the narrow side taper of the continuous casting mold, the definition of which depends equally on the inclinations of both narrow side plates with respect to the casting direction.

Furthermore, the controller of the control loop can also contain filterings which either process the input signal for a control rule contained in the control loop or process the signal determined by the rule rule before it is fed to the controlled system.

The inventive method enables a quick reaction to changing process conditions, since the detection of the narrow side forces that are influenced by the process conditions, in contrast to methods that are based on temperature or heat flow measurements, takes place practically in real time.

The inventive method is also based on an empirical relationship between the narrow side forces on the one hand and the current casting parameters, such as the casting speed, the behavior of the casting powder or the composition of the molten metal on the other hand, this empirical relationship being modeled by the behavior of the controller. The method according to the invention therefore does not require any physical modeling of the effects of the various influencing variables, but rather is based on the measurement of the direct reaction of the casting parameters in the form of the narrow side forces, so that the effects of all relevant casting parameters are taken into account equally and equally quickly.

Thus, a lifting of the strand shell from the inside of the narrow side plates, caused, for example, by excessive cooling and accompanying strand shrinkage, can be detected immediately because the narrow side forces to be applied for a specific control position decrease accordingly. Likewise, an increase in the narrow side forces, which would cause the strand to be crushed and is caused, for example, by the cooling capacity of the metal strand being too low, can be compensated for directly. In this way, an optimal force distribution of the actuators and, accordingly, the largest possible contact area between the strand shell and the inner surfaces of the narrow side plates is achieved without the frictional forces between the strand shell and the inner surfaces of the continuous casting mold being unnecessarily increased.

Furthermore, the method according to the invention ensures good reproducibility, since the adaptation of the narrow side taper to the current production conditions does not require any operator intervention, but only depends on the preset parameters of the controller or on any filtering carried out in the controller.

In a further preferred embodiment of the method according to the invention, the reference pressure P _{ref is} a function of the density of the molten metal melt p _Hq , a mold level h and a dimensionless correction factor S.

The density pi _{iq of} the molten metal is to be understood as the material density of the liquid melt, the physical unit of which is given, for example, in kg / m ³ . The reference pressure P _ref depends on the density of the molten metal pi _iq and on the level of the mold level h

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AT 519 154 B1 2019-12-15 Austrian patent office is defined as the distance of the casting mirror to the exit end of the mold and also contains another dimensionless correction factor S, which can be specified.

The reference pressure P _ref is a parameter of the control process and can also be reset if necessary during the casting process, for example by an operator or by another control system, in order to change the characteristic of the control loop. This makes it possible to take into account a change in the mold level h during the casting process or to react flexibly to changes in the casting parameters, such as a change in the composition of the molten metal, the casting powder or in the heat dissipation of the mold.

An adaptation of the reference pressure can be based, for example, on empirical values based on the recorded casting parameters, as a result of which an advantageous driving style of the continuous casting mold, once determined under certain casting conditions, can be reproduced.

The reference pressure P _ref can, for example, by the expression

P _ref = SP _fer / 2 = S p | _iq gh / 2 are determined, where g is the value of the acceleration due to gravity and P _fer the ferrostatic pressure of the molten metal inside the cast metal strand at the outlet end of the continuous casting mold. Since, due to the laws of physics, the ferrostatic pressure P _{fer increases} linearly in the pouring direction, the ferrostatic pressure averaged over the mold level h, which is referred to as the mean surface pressure P _med , corresponds to half the value of the local ferrostatic pressure P _fer at the foot of the liquid column of height h at the exit end of the mold. A temperature- _related change in density p _Hq can be disregarded if the pouring temperature of the molten metal is only a few degrees above its solidification temperature.

The correction factor S preferably has a value range of 0.7-3 and takes into account the inherent load-bearing capacity of the strand shell which forms, which weakens the effect of the outwardly directed ferrostatic pressure P _{fer of} the molten metal, furthermore the effect of the frictional forces between the narrow side plates and the broad side plates, which counteract the forces applied by the actuators of the narrow side plates and reduce them accordingly, and the friction between the strand shell and the narrow side plates, which due to the narrow side taper has an outward force component in the width direction of the continuous casting mold and depends on the value of the narrow side taper. In addition, the correction factor S can depend on the chosen casting speed v, because in particular the friction between the strand shell and the narrow side plates represents sliding friction and therefore the friction forces that occur depend on the relative speed between the surfaces involved.

At values of S <1, the self-supporting capacity of the strand shell outweighs the frictional forces between the narrow-side and broad-side plates or between the narrow-side plates and the strand shell and is used, for example, in an operating mode in which the broad-side plates counteract only with very little clamping action the narrow side plates are turned on, which is also referred to as soft clamping.

In contrast, values of S> 1 mean that the frictional forces between the narrow-side and broad-side plates or between the narrow-side plates and the strand shell predominate and must be compensated accordingly by the actuators of the narrow-side plates.

The dependence of the correction factor S on the casting speed v can be described, for example, by a table model based on empirical values. S can also be influenced by other factors, e.g. depend on the composition of the molten metal or the casting powder, which can also be shown in an empirically recorded table model.

The above definition of the reference pressure P _ref offers the advantage that it is a

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AT 519 154 B1 2019-12-15 Austrian patent office represents easy-to-use empirical modeling of the reference variable of the control loop according to the invention, which, in addition to the correction factor S, depends only on process parameters which are known in any case and which therefore uses the correction factor S, for example, in relation to new compositions of the molten metal or of the mold powder can be easily expanded and requires no complex physical simulations.

In a further preferred embodiment of the method according to the invention, the mean surface pressure P _{med is given} by the expression

NI N2

Pmed = [^ (Fl, i) + ^ (F ₂ j)] / (2 h - d) i = lj = l, where

Fu the force detected by a measuring element of the control circuit and occurring at the actuator i of the first narrow side plate,

F ₂ , j the force detected by a measuring element of the control circuit and occurring at the actuator j of the second narrow side plate,

N1 the number of actuators of the first narrow side plate,

N2 denotes the number of actuators on the second narrow side plate, h the height of the mold level and d the thickness of the mold.

The mean surface pressure P _med represents an averaging over the forces of all actuators of the two narrow side plates which the actuators exert on the narrow side plates. These forces can advantageously be measured very simply and quickly using methods known from the prior art, as a result of which the control loop can react very quickly to control deviations. In particular, it is possible to control control deviations much more quickly than would be the case with temperature or heat flow-based controls, since force measurements can be carried out within fractions of a second.

In a preferred embodiment of the method according to the invention, the setting of a common narrow side taper for both narrow side plates takes place symmetrically with respect to the casting direction of the continuous casting mold, with specification of the spatial position of the center line of the metal strand in relation to the wide side plates and a value for the casting width b.

For each of the two narrow side plates by means of the actuators acting in the width direction of the continuous casting mold, the spatial arrangement of which is known, the inclination of the narrow side plate with respect to the casting direction and an absolute spatial position can be specified, which - based on the entire continuous casting mold - represents four mechanical degrees of freedom.

If the position of the center line of the metal strand produced with respect to the broad side plates is kept constant by appropriate positioning of the narrow side plates so that the metal strand does not drift in the width direction relative to the broad side plates, this reduces the number of degrees of freedom by one. An additional specification of a distance of the narrow side plates from one another - for example the distance between the ends of the narrow side plates at the casting outlet end, which by definition is identical to the casting width b of the continuous casting mold - reduces the degrees of freedom by a further. Furthermore, if the inclinations of the two narrow side plates are set symmetrically with respect to the casting direction, this represents a restriction to only a single degree of mechanical freedom of the narrow side plates, which is represented by a correspondingly unique value for the narrow side conicity. This creates a clear connection

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AT 519 154 B1 2019-12-15 Austrian patent office between a value for the narrow side taper K _s and the position values of the individual actuators of both the first and the second narrow side plates, so that from a default value for the narrow side taper K _s corresponding position values of the actuators of both narrow side plates in can be clearly determined. In this case, the two narrow side plates of the continuous casting mold are no longer positioned independently of one another, but instead are positioned by a single control loop.

In this context, it is also possible to change the casting width b during the execution of the control process or to leave it constant, and to specify a starting value for the target positions of the individual actuators when they first pass through the control loop. A constant value of the casting width b during the casting process is particularly desirable with regard to the quality of the cast metal strand, since complex measures for adjusting the width of the metal strand, such as e.g. Flame cutting or side upsetting can be omitted.

In a preferred embodiment of the method according to the invention, the controller of the at least one control circuit comprises a control specification with an input variable derived from the control deviation and an output variable, and the actual positions {Xu, X _2j } of the actuators are at least in each cycle of the at least one control circuit one of the first or the second narrow side plate is detected and an actual value l _s for the narrow side taper K _{s is} derived therefrom and this by specifying corresponding target positions {Yu, Y _{2 j} } for the actuators of at least one of the first or the second narrow side plate in one the effect of Narrow-side taper on the controlled system of the at least one control circuit that depicts the mean surface pressure is only reset if there is a difference to the determined actual value.

The detected actual positions of the actuators of the narrow side plates thus represent input variables and the determined target positions for the actuators represent corresponding output variables of the at least one control loop, which are determined anew each time through the at least one control loop.

Therefore, if the actual value l _{s of} the narrow side taper and the manipulated variable determined in the current cycle of the at least one control loop, which is identical to the setpoint value of the narrow side taper K _{s, there} is no need to adjust the narrow side taper via the controlled system. This is particularly advantageous if, when adjusting the narrow side plates, the clamping mechanism for the wide side plates usually has to be actuated, which in this case can be omitted. Such a control cycle can therefore be run through correspondingly quickly, ie within a few milliseconds or faster.

[0082] In a further preferred embodiment of the method according to the invention, the regulator is given a regulation

K _s '= l _s - k Pdif' where

P _dif 'is a variable derived from a control deviation P _{dif of} the control loop,

K _s ' is a variable determined by the control specification of the control loop for determining the manipulated variable K _s and k is a proportionality factor with a value range from 0.001 to 0.1, preferably from 0.005 to 0.02.

The control specification describes the behavior of the control loop as a function of the control deviation and is used to determine the output variable; the meaning and role of the regulation are to be understood in the context of a classic control loop and are therefore well known to the person skilled in the art.

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AT 519 154 B1 2019-12-15 Austrian Patent Office [0084] With this rule specification, control deviations can be parameterized in a very simple way: if the proportionality factor k has a value less than 1, this has the effect that the determined control deviation is weakened in the correction of the output variable of the regulation, while the deviation is increased for values greater than 1.

In a further preferred embodiment of the method according to the invention, the control deviation P _{dif of} the control circuit is first filtered by means of a time-related filter Φ _τ according to

Pdif ' ⁼ Φτ (Ράίί! {Pdifpr), where {Pdifpr is a set of stored values of the control deviation P _dif from a previous cycle of the control loop and reaching back over a time period τ

P _dif 'are an input variable determined by the time-related filter Φ _τ for the regulation of the control loop.

This filtering can consist, for example, of a simple averaging of all the values of the control deviation used. However, it is also conceivable to weight current values more strongly than values from earlier times. For example, the historical values of the control deviation are preferably taken into account over a period of time τ = 5-10 seconds.

This temporal filtering of the control deviation suppresses high-frequency fluctuations in the measurement signal, which can be caused, for example, by incorrect measurements. This prevents incorrect adjustment of the narrow side plates due to incorrect measured values or due to high-frequency interference and helps to stabilize the continuous casting process.

In the event that an adjustment of the narrow side taper is triggered, this can be carried out quickly since, because of the first filtering, which filters out large fluctuations in the control deviation, usually only small changes in the manipulated variable have to be carried out. For example, a change of 0.1% of the narrow side taper at a casting width of 2000mm with a conventional continuous casting mold, the level of which is typically less than 1000mm, only causes an adjustment of less than 2mm in the area of the cast-side actuators. The entire process of such an adjustment, including releasing the clamping of the wide-side plates, moving the narrow-side plates by means of the actuators and re-clamping the wide-side plates, can therefore usually be carried out within a second or even faster, so that a very fast control process is provided.

In a further preferred embodiment of the method according to the invention, the output variable K _s ' is filtered a second time by means of a saturation filter Φε according to

Ks ~ Φδ (Κ _δ , K _sm j _n , K _{s ma} x) where

K _{s is} a value derived by means of the saturation filter Φε for determining the manipulated variable K _s ,

Ks.min is a lower limit for the narrow side taper K _s and

K _s , max are an upper limit for the narrow side taper K _s .

The saturation filter Φε ensures that the narrow side taper K _s regulated by the control loop remains within the permitted range defined by the limit values K _smin and K _smax , for example within 1.1 to 1.2. The limit values K _smin and K _{s max are} parameters of the control method, which are usually fixed, but are

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AT 519 154 B1 2019-12-15 Austrian patent office can also be changed during the casting process. For example, the limit values K _Simin and Ks, _{max can} be changed by an operator or by a control system when changing between two metal batches, if a changed composition of the molten metal requires this.

In a further preferred embodiment of the method according to the invention, the narrow side taper K _{s is matched} by a third filtering of a value K _s derived from the output variable K _s ' of the regulation by means of a hysteresis filter Φ _Η

Ks = 0h (| K _s -Is |; X), where | | the formation of the numerical absolute value and λ denote the threshold value of the hysteresis filter and the derived value K _s corresponds to a signal-technical treatment of the output variable K _s ' preceding the third filtering of the regulation.

According to a two-point controller, the manipulated variable of the control loop is only changed if the value K _s determined in the current cycle of the control loop differs in amount by at least the value λ from the current actual value l _{s of} the narrow side taper. This means that the actuators of the narrow side plates are only adjusted if the newly calculated default value for the narrow side taper differs from the existing value, for example by more than 0.05, so that, for example, only slight fluctuations in the production conditions affect the quality of the metal strand produced have no effect, the narrow side plates do not have to be adjusted unnecessarily and in particular the clamping of the wide side plates does not have to be released, which contributes to a constant stability of the continuous casting process and to the speed of the control process.

[0093] The invention further relates to a

Device for setting a narrow side taper K _{s of} a continuous casting mold for the production of a metal strand, in particular for carrying out one of the methods described, the continuous casting mold comprising a first and a second narrow side plate, on each of which at least two position-controlled actuators for positioning the respective narrow side plate at different distances from the are arranged on the pouring end of the continuous casting mold and the device has a control unit and devices for detecting the forces occurring during the operation of the continuous casting mold in the direction of action of each actuator, characterized in that the control unit is set up for a control circuit, the control circuit

a reference pressure P _ref as a reference variable,

an average surface pressure P _med between the narrow side plates and the metal strand as a controlled variable, the average surface pressure P _{med being able to be determined} from the forces occurring in the direction of action of the actuators,

a controller by means of which, depending on a control deviation P _dif = P _{ref -P med} as input variable, the narrow side taper K _s can be determined as a manipulated variable of the control loop, and

- A controlled system, by means of which the position of the first and / or the second narrow side plate can be adjusted according to the narrow side taper K _s by means of the actuators.

The advantageous embodiments of the device according to the invention for setting a narrow side taper of a continuous casting mold essentially correspond to those of the method according to the invention.

In a preferred embodiment of the device according to the invention, at least one of the actuators is a hydraulically moved actuator.

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AT 519 154 B1 2019-12-15 Austrian Patent Office [0096] Such actuators can be moved very quickly since no gear is required and are sufficiently known from the prior art.

In a particularly preferred embodiment of the device according to the invention, at least one of the hydraulically moved actuators is a double-acting hydraulic cylinder.

Double-acting hydraulic cylinders offer the advantage that the force applied by the respective actuator can be determined very easily by two pressure sensors per actuator, since the force is determined by the differential pressure between the two chambers and the cross-sectional area of the piston of the double-acting hydraulic cylinder. It is therefore also possible to retrofit an existing continuous casting mold, which already has hydraulic cylinders of this type for adjusting the narrow side plates, to carry out the method according to the invention in a simple and cost-effective manner, since only sensors for detecting the corresponding pressures and the travel positions of the corresponding actuators have to be installed.

[0099] In a further embodiment of the device according to the invention, at least one of the actuators has an electrical rotary drive.

Such actuators allow easy determination of the actuator position based on the position of the drive axis of the electrically operated motor or an axis of the transmission, which is usually used between the motor and the linearly moving point of application of the actuator in question. The forces occurring at the points of application of the actuators can e.g. are measured using strain gauges.

In a further preferred embodiment of the device according to the invention, at least one of the electrically driven actuators is a linear motor.

[00102] Linear motors do not require a gear and therefore have no mechanical play. Furthermore, they offer the advantage that the force occurring can be determined directly from the force-speed characteristic or from the force-current characteristic without additional force sensors.

The above-described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more clearly understandable in connection with the following description of exemplary embodiments which are explained in more detail in connection with the drawings. Here show [00104] [00106] [00107]

FIG 1a

1b

1c

2 shows a perspective view of a continuous casting mold, a section through a continuous casting mold normal to the width direction, a section through a continuous casting mold normal to the thickness direction, schematically the forces occurring in the width direction of the mold, FIG. 3 [00109] FIG. 4 shows the signal flow of a narrow side plate of a Control loop according to the invention and the schematic structure of a control loop according to the invention of a narrow side plate with two actuators.

FIG 1a shows in an oblique view the arrangement of the broad side plates 2, 2 'and the first and second narrow side plates 4 and 4' of a continuous casting mold 1, the two narrow side plates 4, 4 'being slidably arranged along the inner surfaces of the broad side plates 2, 2' are. The back-up plates of the individual mold plates and the actuators for adjusting the narrow side plates are not shown in this view.

Furthermore, the direction vectors of the thickness direction D, the width direction B and the casting direction G are shown in FIG. 1a in their spatial position in relation to the continuous casting mold 1, the vectors D, B and G forming an orthogonal, right-handed coordinate system.

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AT 519 154 B1 2019-12-15 Austrian Patent Office [00112] At the end 3 on the pouring side, molten metal is added with the addition of casting powder into the interior of the continuous casting mold 1, where the metal melt is transported further in the direction of casting G and at the exit end 3 'in the form of a partially solidified one Metal strand 5 is pulled out of the mold 1. The metal strand 5 has a rectangular cross section with respect to the normal plane to the casting direction G, the short side of which is oriented in the thickness direction D and the long side in the width direction B.

1b shows a section through the continuous casting mold 1 from FIG. 1a normal to the width direction B, in which the broad side plates 2, 2 'inclined relative to the casting direction G with the backing plates 7, 7' fastened thereon and the trapezoidal shape of the second narrow side plate 4 'can be seen are.

The distance f of the inner surfaces of the broad side plates 2, 2 'at the pour-side end 3 is greater than the corresponding distance d at the exit-side end 3' of the continuous casting mold 1, d being also referred to as the casting thickness, since the cast metal strand 5 (in FIG 1b)) with this thickness emerges from the interior enclosed by the continuous casting mold 1.

1c shows a section through the continuous casting mold 1 from FIG. 1a normal to the thickness direction D. The narrow side plates 4, 4 ', which are inclined relative to the casting direction G, can be seen, with the backing plates 6, 6' attached to them, and the rectangular shape of the broad side plate 2, along the inside of which the narrow side plates 4, 4 'can be displaced, can be seen.

The distance e of the inner surfaces of the narrow side plates 4, 4 'at the end 3 on the pouring side is again greater than the corresponding distance b at the end 3' of the continuous casting mold 1, where b is referred to as the casting width.

On the outer sides of the narrow side plates 4, 4 ', an upper actuator Α _1Ί or A ₂ , i engages near the casting-side end 3 of the continuous casting mold 1 and a lower actuator A ₁₂ or A _2i2 near the _exit-side end 3' the continuous casting mold 1. By means of the force acting in the width direction B actuators _Α 1Ί or A _12, the first narrow side plate 4 with regard to methods of their inclination to the casting direction G and its position in the width direction B and are held in a certain position, wherein the upper actuator A _12, the force F ^ and the force F ₁₂ occurs on the lower actuator A ₁₂ along the effective direction of the respective actuator. Accordingly, by means of the actuators A ₂₁ and A is the inclination and the position of the second narrow side plate 4 is set _{2 2} 'or maintained, at the upper actuator A _21, the force F ₂₁ and the lower actuator A _{2, 2,} the force F _{2, 2 occurs} in the effective direction of the respective actuator.

With the above definitions and the distances shown in FIG 1b and FIG 1c, the broad side taper K _b and the narrow side taper K _{s is} calculated as a dimensionless quantity, in each case in percent, in the present example

K _b = (f - d) x 100 / H

K _s = (e-b) x 100 / b [00119] However, other calculation rules for the conicity are also conceivable, for example the narrow side taper K _{s can} also be related to the mold height H.

2 shows a section normal to the thickness direction D through a continuous casting mold 1, the first and second narrow side plates 4 and 4 'of which each have two actuators (Α _υ , A ₁₂ ) and (A ₂ , i, A _{2 2} ) are, however, the inclination of the narrow side plates 4 and 4 'is not shown. Along the inner surface of the first narrow side plate 4, the course of the ferrostatic pressure P _{fer of} the metal melt 10, which increases linearly in the casting direction G, is shown schematically, while along the inner surface of the second narrow side plate 4 'the strand shell 13 growing in the casting direction G can be seen. Furthermore, the center line M denotes the line of symmetry of the metal strand 5 with respect to the width direction B of the continuous casting mold 1.

Near the pour-side end 3 of the continuous casting mold 1, the surface of the poured molten metal 10 is also referred to as a mold level 12, which is in an from / 27th

AT 519 154 B1 2019-12-15 Austrian patent office stand h - the so-called mold level - is located above the outlet-side end 3 'of the continuous casting mold 1. At the exit end 3 ', the partially solidified metal strand 5 is pulled out of the continuous casting mold 1, the strand shell 13 already formed being supported in the width direction B by lateral strand guide rollers 14 and 14'.

With Fu and F ₂ , i as in FIG 1c, the forces of the upper actuators Au and A ₂ , i (not shown in FIG 2) are referred to, which near the pouring end 3 on the respective narrow side plate 4 or 4 ' be transmitted. Correspondingly, F ₁₂ and F ₂ , ₂ symbolize the forces of the exit-side actuators A ₁₂ and Ä ₂ , ₂ .

Is shown in a section normal to the direction of thickness D half of a continuous casting mold 1 according to the invention to the center line M and the control connection to a control unit 8, the first narrow side plate 4 being moved with the help of two actuators Au and A ₁₂ can. The other half of the continuous casting mold 1, which comprises the second narrow side plate 4 'and corresponding actuators A ₂₁ and A _{2 2} , is connected to the control unit 8 in a manner corresponding to the first half shown, but is not shown in FIG. 3. In the specific example, the actuators Α _υ and A _{12 are also designed} as double-acting hydraulic cylinders.

The liquid molten metal 10, which is introduced during the continuous casting near the upper, casting-side end 3 in the continuous casting mold 1, forms with its surface the mold level 12 at a distance corresponding to the mold level h above the lower, exit-side end 3 'of the continuous casting mold 1 off. In the casting direction G below the first narrow side plate 4, the solidified strand shell 13 is supported by lateral strand guide rollers 14.

The actuator Α _1ί engages near the upper, casting-side end 3 of the continuous casting mold 1 on the first narrow side plate 4 and can move this at this point of attack in the width direction B; analogously to this, the first narrow side plate 4 can also be moved in the width direction B by the actuator A ₁₂ , which acts on the first narrow side plate 4 in the vicinity of the lower, outlet-side end 3 '.

[00126] For detecting the instantaneous position of the first narrow side plate 4, the respective position values Xu and X transmitted by the actuators Au and A _{12 12} to the control unit 8, which are determined by the corresponding position sensors 16 of the respective actuator. In addition, the pressures of the two chambers of each double-acting hydraulic cylinder are detected by means of corresponding pressure sensors 11 and transmitted to the control unit 8. The forces Fu and F ₁₂ with which the actuators Au and A _{12 act} on the first narrow side plate 4 can be determined from the difference between these pressures. Furthermore, the actuators A _1f1 and A _{12 are} acted upon by hydraulic drive units 9 with corresponding amounts of hydraulic fluid, so that the pistons of the actuators are moved in accordance with the desired positions Υ _1Ί and Y ₁₂ determined by the control unit 8. The hydraulic drive units 9 can be, for example, hydraulic pumps or hydraulic valves which provide the volume of hydraulic fluid required in each case. For the second narrow side plate 4 '(not shown in FIG. 3), the explanations apply mutatis mutandis with regard to the actual positions X ₂₁ and X ₂₂ and the forces F ₂₁ and F _{2 2 of} the actuators A ₂₁ and A _{2 2} and for those specified by the control unit 8 Target positions Y ₂₁ and Y ₂₂ .

4 shows an embodiment of a control circuit 15 for setting the narrow side taper K _s according to the inventive method, the control circuit 15 in addition to the actual regulation 25 a first time filtering 22 of the control deviation P _dif , and a second filtering 23 in relation to comprises the permissible maximum values and a third filtering 24 with regard to a desired hysteresis behavior of K _s .

A cycle of the control circuit 15 runs as follows for a continuous casting mold 1, comprising a first and a second narrow side plate 4 and 4 ':

- The forces F ^ transmitted by the actuators A ^ to the first narrow side plate 4 and the forces transmitted by the actuators A ₂ j to the second narrow side plate 4 '

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AT 519 154 B1 2019-12-15 Austrian patent office

F ₂ , j are recorded in a measuring element 26, from which the control variable of the control circuit 15 is determined in the form of an average surface pressure P _med (with pressure as the physical unit) together with the values of the mold level h and the casting thickness d. The indices i and j comprise the value range {1, ... N1} and {1, ... N2}, where N1 and N2 the number of actuators on the first and second narrow side plates 4 and 4 '. describe.

- A reference pressure P _ref from the density of the liquid molten metal pi _iq , the mold level h and a dimensionless correction factor S is used as the reference variable of the control circuit 15. The values of h, pi _iq and S can either be predefined for each cast batch or changed during the casting process. In particular, the current mold level h can be measured and the instantaneous value obtained can be transmitted to the control circuit 15.

- The current value of the control deviation P _{dif of} the control circuit 15 according to

Pdif ^- Pref Pmed is determined and stored in a control unit 8 (not shown in FIG. 4) and fed to the controller 21 of the control circuit 15, the controller 21, in addition to the actual regulation 25 in the present example, a first, second and third filtering 22, 23 and 24 includes.

- In the next step, from the current value of P _dif together with stored values of the control deviation from previous runs through the control circuit 15 by means of a first filtering 22, which uses a time-related filter Φ _τ , which spans a past time period τ filtered value P _dif 'is determined from the control deviation, the filter Φ _τ being used to filter out short-term deviations and high-frequency interference and thus to determine a time-smoothed value of the control deviation.

- In the regulation 25 of the control loop, the actual values of the positions Χ _{υ of} the actuators Α _{υ of} the first narrow side plate 4 and the actual values of the positions X _{2j of} the actuators A _{2j of} the second narrow side plate 4 'with the help of position sensors 16 (in FIG. 4 not shown) recorded and an actual value l _s for the narrow side taper of the continuous casting mold 1 is determined therefrom in accordance with the geometric relationships of the continuous casting mold 1. An output variable K _s 'of the regulation 25 is determined from the actual value l _s and from the time-filtered value P _dif ' in such a way that the control deviation P _{dif is} counteracted in the controlled system 20 via the action of the actuators Α _υ or A _2j .

- Then in a second filtering 23 by means of a saturation filter Φ _δ , which contains the permitted lower limit K _Simin or upper limit K _s , _m ax as a parameter for the narrow side taper K _s , a derived from the output variable K _s ' of the rule 25 Value K _s determined. This prevents the narrow side taper K _{s from exceeding} or _falling below the predefined limit values in the case of large or permanently persistent control deviation P _dif , which would result in particular in the case of a proportional control in control regulation 25.

- Then in a third filtering 24 by means of a hysteresis filter Φ _Η from the derived value K _s the newly set value for the narrow side taper K _{s is} determined, which at the same time represents the manipulated variable of the control circuit 15. The hysteresis filter Φ _{Η contains} a parameter λ that describes the threshold value of the hysteresis filter. This parameter specifies the minimum difference between the manipulated variable K _s and the associated actual value l _s , from which an adjustment of the narrow side plates 4 or 4 'is actually carried out. Differences below the threshold value λ are suppressed by the hysteresis filter Φ _Η by setting the manipulated variable K _{s to} the actual value l _s .

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AT 519 154 B1 2019-12-15 Austrian Patent Office [00136] - In the control system 20 of the control circuit 15, the corresponding target positions Yu and Y ₂ j of the actuators Α _υ are made from the new default value for the narrow side taper K _s and from the casting width b or A _{2j of} the first or second narrow side plates 4 or 4 'is determined and the narrow side plates are adjusted by adjusting the actuators accordingly, the adjustment being carried out only if the manipulated variable K _s and the associated actual value l _s differ.

Although the invention has been illustrated and described in detail by means of preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

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AT 519 154 B1 2019-12-15 Austrian patent office

LIST OF REFERENCE NUMBERS

I 2, 2 '3 3' 4 4 '5 6, 6' 7, 7 '8 9 10 II 12 13 14, 14' 15 16 20 21 22 23 24 25 26 Au ^A 2, j ^A 1.1 Al, 2 A ₂ , i ^A 2.2 b B d D Continuous casting mold, broad side plate, pour-side end, outlet-side end, first narrow side plate, second narrow side plate, metal strand Back plate, narrow side, back plate, broad side control unit, hydraulic drive unit, molten metal, pressure sensor, device for force measurement, mold level, strand shell, strand guide rollers, control loop, position sensor, control path, controller, first filtering, second filtering element, third filtering, regulation specification Actuator i of the first narrow side plate Actuator j of the second narrow side plate, cast-side actuator of the first narrow side plate, exit-side actuator of the first narrow side plate, cast-side actuator of the second narrow side plate, exit-side actuator of the second narrow side plate, casting width width direction casting thickness thickness direction ef Fi, i F ₂ j F 1.1 Fl, 2 F ₂ , i Distance on the pouring side of the narrow side plates Distance on the pouring side of the broad side plates Force on actuator i of the first narrow side plate Force on actuator j of the second narrow side plate Force on the pouring side actuator of the first narrow side plate Force on the outlet side actuator of the first narrow side plate Force on the pouring side actuator of the second narrow side plate

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AT 519 154 B1 2019-12-15 Austrian patent office

F ₂ , 2 force on the outlet-side actuator of the second narrow side plate

Φ _Η hysteresis filter

Φ ₃ saturation filters

Φ _τ time-related filter

G Casting direction h Casting level height

H Mold height i Index with respect to the first narrow side plate l _s Actual value of the narrow side conicity j Index with respect to the second narrow side plate

K _s narrow side taper, manipulated variable

K _s ' output variable of the regulation

K _s derived value

Ks, _min lower limit for narrow side taper

K _s , max upper limit for narrow side taper λ threshold value

M center line

N1 Number of actuators on the first narrow side plate

N2 Number of actuators on the second narrow side plate

P _{dif system} deviation

P _dif 'filtered value of the control deviation, input variable of the control regulation

P _med mean surface pressure, controlled variable

P _ref reference _pressure, reference variable

Pi _iq density of the molten metal

S dimensionless correction factor τ time span

Xu actual position of the actuator i of the first narrow side plate

X ₂ j Actual position of the actuator j of the second narrow side plate

Χ _{1Ί Actual} position of the casting-side actuator of the first narrow side plate

X ₁₂ Actual position of the outlet-side actuator of the first narrow side plate

X ₂₁ Actual position of the actuator on the pouring side of the second narrow side plate

X ₂₂ Actual position of the outlet-side actuator of the second narrow side plate

Yu target position of the actuator i of the first narrow side plate

Y _{2j target} position of the actuator j of the second narrow side plate

Υ _{1Ί Target} position of the casting-side actuator of the first narrow side plate

Y ₁₂ target position of the outlet-side actuator of the first narrow side plate

Y ₂₁ Target position of the casting-side actuator of the second narrow side plate

Y _{2 2} Target position of the outlet-side actuator of the second narrow side plate

Claims (14)

1. Method for setting a narrow side taper (K _s ) of a continuous casting mold (1) for the production of a metal strand (5) with the aid of at least one control circuit (15), the continuous casting mold (1) comprising a first narrow side plate (4) and a second narrow side plate ( 4 '), - wherein on the first narrow side plate (4) a plurality (N1) of position-controlled actuators (Au) with ie {1, ..., N1} for positioning the first narrow side plate (4) and on the second narrow side plate (4 ') a plurality ( N2) position-controlled actuators (A ₂ j), each with {1, .N2} for positioning the second narrow side plate (4j, each at a different distance from the casting-side end (3) of the continuous casting mold (1), and - In the effective direction of each actuator (Au, A ₂ j) during operation of the continuous casting mold (1), corresponding forces (Fu, F _2j ) with ie {1, ..., N1} and each {1, .., N2} occur, characterized in that during a cycle run through the at least one control circuit (15) - a reference pressure (P _ref ) as a reference variable and - An average surface pressure (P _me d) between the narrow side plates (4, 4 ') and the metal strand (5) as a control variable, the mean surface pressure (P _med ) being determined from the forces (Fu, F ₂ j) and that - A controller (21) as a function of a control deviation (P _dif ) = (P _ref ) - (P _me d) determines the narrow side taper (K _s ) as the manipulated variable of the control circuit (15) as an input variable and that - The position of the first and / or the second narrow side plate (4, 4j) is adjusted according to the narrow side taper (K _s ) over a controlled system (20) by means of the actuators (Au, A _2j ). 2. The method of claim 1, _wherein the reference pressure (P _ref ) is a function of the density (pi _iq ) of the molten metal (10), a mold level (h) and a dimensionless correction factor (S). 3. The method according to any one of the preceding claims, wherein the mean surface pressure (Pmed) by the expression NI N2 Pmed = [^ (Fi, i) + ^ (F ₂ , j)] / (2-hd) i = lj = l with a casting level height (h) and a casting thickness (d) of the continuous casting mold (1). 4. The method according to any one of the preceding claims, wherein the setting of a common narrow side taper (K _s ) for the first and the second narrow side plate (4, 4 ') symmetrically with respect to the casting direction (G) of the continuous casting mold (1) with the specification spatial position of the center line (M) of the metal strand (5) in relation to the broad side plates (2, 2 j and the casting width (b). 5. The method according to any one of the preceding claims, wherein the controller (21) is a control law (25) with one of the control deviation (P _dif) derived input variable (P _di f) and an output (K _s'), and wherein the actual positions (Xu, X _2j ) of the actuators (Au, A _2j ) of at least one of the first or the second narrow side plates (4, 4 ') are recorded in each cycle of the control circuit (15), - an actual value (Is) of the narrow side taper (K _s ) is derived from this and - In a control system (20) of the control circuit (15), which maps the effect of the narrow side taper (K _s ) on the mean surface pressure (P _me d), the narrow side taper (K _s ) 21/27 AT 519 154 B1 2019-12-15 Austrian patent office only by re-setting at least one of the first or second narrow side plates (4, 4 ') for the actuators (Au, A _2j ) by specifying the corresponding target positions (Yu, Y ₂ j) if there is a difference to the determined actual value (l _s ). 6. The method according to claim 5, wherein the regulation (25) is K _s '= 1 _s - k P _dif ', where k is a proportionality factor with a range of values from 0.001 to 0.1. 7. The method according to any one of claims 5 or 6, in which from the control deviation (P _dif ) by a first filtering (22) by means of a time-related filter (Φ _τ ) the input variable (P _di f) according to the regulation (25) Pdif ' ⁼ Φτ (Ράίί] {Pdifjl), is determined, where {P _dif } T is a set of stored values of the control deviation (P _dif ) from previous cycles of the control loop (15) which go back over a period of time τ. 8. The method according to any one of claims 5 to 7, in which from the output variable (K _s ') of the regulation (25) by a second filtering (23) by means of a saturation filter (Φ ₅ ) a derived value (K _s ) according K _s - Φ3 (Κ _δ , K _sm j _n , K _smax ) is determined, where K _{Simin is} a lower limit and K _s , _m ax is an upper limit for the narrow side taper (K _s ). 9. The method according to any one of claims 5 to 8, in which by a third filtering (24) a value (K _s ) derived from the output variable (K _s ') of the regulation (25) by means of a hysteresis filter (Φ _Η ) the narrow side taper ( K _s ) according to K _s = Φ _η (| Κ ₅ - l _s |; λ), is determined, where | | the formation of the numerical absolute value and λ denote the threshold value of the hysteresis filter (Φ _Η ). 10. Device for setting at least one narrow side taper (K _s ) of a continuous casting mold (1) for the production of a metal strand (5), in particular for carrying out a method according to claims 1 to 9, wherein the continuous casting mold (1) has a first narrow side plate (4) and comprises a second narrow side plate (4 '), - wherein on the first narrow side plate (4) a plurality (N1) of position-controlled actuators (Au) with ie {1, ..., N1} for positioning the first narrow side plate (4) and on the second narrow side plate (4 ') a plurality ( N2) position-controlled actuators (A _2j ), each with {1, .., N2} for positioning the second narrow side plate (4 ') at a different distance from the casting-side end (3) of the continuous casting mold (1), and - The device via a control unit (8) and devices (11) for detecting the forces (Fu, F _2j ) occurring during operation of the continuous casting mold (1) in the effective direction of the respective actuators (Au, A ₂ j) with ie {1 , .., N1} and each {1, .., N2}, characterized in that the control unit (8) is set up for at least one control loop (15), the control loop (15) a reference pressure (P _ref ) as a reference variable, an average surface pressure (P _me d) between the narrow side plates (4, 4 ') and the metal strand (5) as a control variable, the mean surface pressure (P _med ) being able to be determined from the forces (Fu, F ₂ , j), - A controller (21) through which, depending on a control deviation (P _dif ) = (P _ref ) (Pmed) as the input variable, the narrow side taper (K _s ) can be determined as the manipulated variable of the control circuit (15), and 22/27 AT 519 154 B1 2019-12-15 Austrian patent office - A controlled system (20), by means of which the position of the first and / or the second narrow side plate (4, 4j) can be adjusted according to the narrow side taper (K _s ) by means of the actuators (Au, A ₂ j). 11. The device according to claim 10, wherein at least one of the actuators (Au, A ₂ j) is a hydraulically moved actuator. 12. The apparatus of claim 11, wherein at least one of the hydraulically moved actuators (Au, A ₂ j) is a double-acting hydraulic cylinder. 13. The apparatus of claim 11, _wherein at least one of the actuators (Au, A _2j ) has an electrical rotary drive. 14. The apparatus of claim 11, in at least one of the electrically driven actuators (Au, A ₂ j) is a linear motor.