DE102020209794A1 - Process for controlling or regulating the temperature of a cast strand in a continuous casting plant - Google Patents

Abstract

The invention relates to a method for controlling or regulating the temperature of a cast strand (10) in a continuous casting installation (12), the cast strand (10) being guided through a supporting strand guide (16) of the continuous casting installation (12 ), which has at least one segment (1, 2, 3, 4) with secondary cooling, is guided along a conveying direction (F), the secondary cooling being adjusted by a control or regulation unit (17) and thus the surfaces of the cast strand ( 10) are cooled, with a temperature field being calculated for the cast strand along its conveying direction (F) within the supporting strand guide and a position of the sump tip (SP) of the cast strand (10) being determined therefrom, with the control or Control unit (17) for a material to be cast of the cast strand (10), a spray plan with water quantities for various control circuits of the secondary cooling, which is on the top rfläche act on the cast strand are stored.

Description

The invention relates to a method for controlling or regulating the temperature of a cast strand in a continuous casting plant according to the preamble of claim 1 and claim 9 respectively.

In the operation of continuous casting plants, it is state of the art to cool the cast strand after exiting the mold in the so-called secondary cooling of a supporting strand guide of such plants until the cast strand has completely solidified. This cooling process plays an important role in the resulting quality of the cast strand and the products made from it. Complete solidification of the cast strand should be achieved within the supporting strand guide that supports the cast strand with the core still liquid.

The operation of the secondary cooling of a continuous casting plant is usually realized with spray or cooling water, whereby the amount of water that is applied to the surfaces of the cast strand is adjusted based on spray schedules. The course of these spraying schedules can vary depending on the material of the material to be cast, and e.g. depending on certain cooling zones of the supporting strand guide and/or the casting speed. Depending on the material and the selected casting speed, a spray plan is then selected by an operator of the continuous casting plant and the secondary cooling for applying the spray or cooling water to the surfaces of the cast strand to be cooled is thus set. For example, higher (= warmer) spray schedules can be used at low casting speeds. Conversely, lower (= colder) spray schedules should generally be used at higher casting speeds in order to achieve greater cooling of the cast strand so that it solidifies within the supporting strand guide.

As already explained above, it is of great importance in the operation of a continuous casting plant that the cast strand solidifies completely within the supporting strand guide and does not run out of this supporting strand guide with its sump tip. For this reason, a selected area is provided for the supporting strand guide, in which the sump tip of the cast cast strand should lie.

During the casting of slabs, blooms, billets, etc., there can be constant changes in parameters such as casting temperature, water inlet temperature, heat dissipation in the mold, which affects the casting process and thus makes it necessary to regulate the temperature and position in relation to the sump tip of the cast strand , since there are no stationary conditions. The secondary cooling and the casting speed are suitable as manipulated variables for position control in continuous casting.

According to the state of the art, it is known in connection with the amounts of water for the secondary cooling of a continuous casting plant to use so-called spray plans for this purpose, with which the amounts of spray water that are applied or sprayed onto the surfaces of a cast strand for the purpose of cooling are determined as a function of different casting speeds. be injected. The use of such spray schedules can be problematic for position control during continuous casting in relation to the sump tip of the cast strand in that constant water quantities are provided over a sub-range of the speed support points or over the entire control range of a spray schedule.

The object of the invention is to create a technology for the continuous casting of metals with which the position of the bottom tip of a cast strand can be reliably maintained at a specific target position or in a specific target range of the supporting strand guide of a continuous casting plant with simple means, and also the energy content of the cast strand can be optimized.

This object is achieved by a method having the features of claim 1 and claim 9, respectively. Advantageous developments of the invention are defined in the dependent claims.

A method according to the present invention serves to control or regulate the temperature of a cast strand in a continuous casting plant. According to a first embodiment of the method, the cast strand, after continuously emerging from a mold, is guided along a conveying direction by a supporting strand guide of the continuous casting plant, which has at least one segment with secondary cooling, with the secondary cooling being adjusted by a control or regulation unit and so that the surfaces of the cast strand are cooled. A temperature field is calculated for the cast strand along its conveying direction within the supporting strand guide and a position of the sump tip of the cast strand is determined from this, with a spray plan with water quantities for various control circuits of the secondary cooling being stored in a memory of the control or regulation unit for a material of the cast strand to be cast. the act on the surface of the cast strand are stored. This method is characterized in that in a step (a) it is checked whether the position of the bottom tip of the cast strand is within a predetermined permissible range within the supporting strand guide. Subsequently, in a step (b1), the following is carried out: If the position of the bottom tip of the cast strand is outside the predetermined permissible range and instead is in a warm-critical range of the supporting strand guide: Increase in the cooling capacity of the secondary cooling by using a virtual casting speed greater than the actual set casting speed (v _current ) is formed, whereby the secondary cooling is controlled with the water values of the spray plan, taking this virtual casting speed into account, or: If the position of the sump tip is outside the predetermined permissible range and instead is in a cold-critical range of the supporting strand guide: Reduction the cooling capacity of the secondary cooling system by forming a virtual pouring speed that is smaller than the actually set pouring speed (v _current ), the secondary cooling being controlled with the water values of the spray plan is carried out taking this virtual pouring speed into account.

According to a second embodiment, the invention provides a method for controlling or regulating the temperature of a cast strand in a continuous casting plant, in which the cast strand, after continuously emerging from a mold, is guided along by a supporting strand guide of the continuous casting plant, which has at least one segment with secondary cooling a conveying direction, the secondary cooling being set by a control or regulation unit and the surfaces of the cast strand being cooled as a result. A temperature field is calculated for the cast strand along its conveying direction within the supporting strand guide and a position of the sump tip of the cast strand is determined from this, with a spray plan with water quantities for various control circuits of the secondary cooling being stored in a memory of the control or regulation unit for a material of the cast strand to be cast. acting on the surface of the cast strand are stored. This method is characterized in that in a step (a) it is checked whether the position of the bottom tip of the cast strand is within a predetermined permissible range within the supporting strand guide. Subsequently, in a step (b2), the following is carried out: If the position of the bottom tip of the cast strand is in the predetermined permissible range of the supporting strand guide and has not changed within a predetermined second time (t _v2 ): reducing the cooling capacity of the secondary cooling , in that a virtual pouring speed is formed that is lower than the actually set pouring speed (v _current ), the secondary cooling being controlled with the water values of the spray plan, taking this virtual pouring speed into account.

The implementation of a method according to the present invention provides for the use of at least one spray schedule with which the respective quantities of cooling liquid, in particular in the form of water, are defined as a function of different casting speeds for the secondary cooling of a continuous casting plant and its associated control circuits of spray nozzles. In addition, it can also be provided that there are also separate injection plans for different materials or groups of materials from which the cast strand is produced. In any case, the invention is based on the essential finding that, in order to set a quantity of cooling liquid or cooling water for the secondary cooling on the basis of the current, i.e. the actually set, casting speed, a virtual casting speed is then formed, namely as a function of the check in steps (a) and the knowledge obtained therefrom as to whether or not the position of the bottom tip of the cast strand is within a predetermined permissible range within the supporting strand guide. Taking this virtual casting speed into account, the secondary cooling is then controlled with the water values of the said spray plan. In other words, in the method according to the invention, the amount of cooling liquid or cooling water for the secondary cooling is not determined by the current casting speed, but by the virtual casting speed formed on the basis thereof. In the course of this it can be provided that the casting speed for the cast strand remains unchanged.

At this point it is pointed out separately that within the meaning of the present invention, a virtual casting speed can be formed in such a way that a value for an actually set casting speed, which is known from a spray plan, is either increased or decreased by a fixed amount , or that a preferably linear interpolation is carried out in relation to two constant values for the casting speed, which are known from a spray plan. As explained, the value of such a formed virtual casting speed then forms the basis for controlling the secondary cooling with respectively adapted water values.

A method according to the present invention is based on the fact that the sump top of a cast strand is not exactly at a specific position, but instead is within a certain interval of the supporting strand guide, referred to herein as a predetermined allowable range. This also achieves the advantage of a stable casting process.

In an advantageous development of the first embodiment of the method according to the invention, it can be provided that the virtual casting speed compared to the actually set casting speed (v _current ), depending on the position of the sump tip in the warm-critical area or in the cold-critical area of the supporting strand guide, by a fixed Amount that depends on a maximum possible casting speed is increased or decreased, for example by the amount of at least 0.2 m/min. This has the advantage that there is a significant change in the amounts of water discharged onto the cast strand by the secondary cooling and the position of the sump tip changes or shifts accordingly in the direction of the predetermined permissible range. The following example: If the position of the sump tip is in the hot-critical area of the supporting strand guide, the virtual casting speed is selected to be at least 0.2 m/min higher than the casting speed that is actually set, in order to increase the cooling capacity in the secondary cooling and in As a result, to achieve a displacement of the sump tip of the cast strand into or back into the predetermined permissible range. Otherwise, namely if the position of the sump tip should be in the cold-critical area of the supporting strand guide: In this case, the virtual casting speed is set at least 0.2 m/min lower than the casting speed actually set, so that there is a reduction in the cooling capacity in the secondary cooling is reached and, as a result, a displacement of the sump tip of the cast strand is adjusted into the predetermined permissible range.

In an advantageous development of the first embodiment of the method according to the invention, it can be provided that if it should be determined in step (b1) that the sump tip of the cast strand is in a safety range of the warm-critical range, then the virtual casting speed is reduced by a fixed amount, which is is dependent on the maximum possible casting speed, is increased, for example by at least 0.5 m/min. This achieves the advantage that the cooling capacity of the secondary cooling is increased considerably in a very short time in order to achieve a rapid shift of the sump tip of the cast strand out of the hot-critical range and back into the predetermined permissible range.

In an advantageous development of the first embodiment of the method according to the invention, the virtual casting speed is reduced by a fixed amount, which depends on a maximum possible casting speed, if the position of the sump tip should be in the cold-critical area of the supporting strand guide and a distance of 2 meters or more to the predetermined allowable range. For example, the virtual casting speed is reduced by at least 0.5 m/min. In this way, a reduction in the cooling capacity for the secondary cooling is advantageously achieved, with a corresponding rapid shifting of the sump tip of the cast strand back into the predetermined permissible range.

In an advantageous development of the first embodiment of the method according to the invention, the virtual casting speed is reduced by a fixed amount that depends on a maximum possible casting speed, for example by at least 0.4 m/min, if the position of the sump tip is in the cold-critical area of the supporting strand guide should be at a distance of between 1 meter and 2 meters from the predetermined permissible range. The result of this is that the cooling capacity for the secondary cooling is reduced, with the result that the sump tip of the cast strand is shifted back into the predetermined permissible range.

In an advantageous development of the first embodiment of the method according to the invention, the virtual casting speed is reduced by a fixed amount, which depends on a maximum possible casting speed, if the position of the sump tip should be in the cold-critical area of the supporting strand guide and at the same time one of the predetermined permissible range distance between 0.5 meter and 1 meter. For example, the virtual casting speed is reduced by an amount of at least 0.3 m/min. This also ensures that the cooling capacity for the secondary cooling is reduced and the position of the sump tip is then correspondingly shifted back into the predetermined permissible range.

In an advantageous development of the invention, it can be provided that steps (a) and (b1) are carried out repeatedly after a predetermined first time (t _v1 ) has elapsed. In this case, the predetermined first time (t _v1 ) is determined from the quotient of the length of the supporting strand guide and the actually set casting speed (v _current ).

An optimization of the first embodiment of the method according to the invention can be achieved by a step (b2) performed subsequent to step (b1). In detail, this step (b2) provides: If the position of the bottom tip of the cast strand is in the predetermined permissible range of the supporting strand guide and has not changed within a predetermined second time (t _v2 ): reducing the cooling capacity by a virtual casting speed smaller than the actually set pouring speed (v _current ), whereby the secondary cooling is controlled with the water values of the spray plan, taking this virtual pouring speed into account.

With the execution of step (b2), the advantage is achieved for a method according to the invention that the cast strand has a high heat content when leaving the supporting strand guide. This aspect is particularly important in the case of plant types in which a cast strand produced does not first cool down, but is further processed directly in a subsequent hot rolling mill. Plant types of this type can be CSP plants or plants for thick slabs, billets, blooms or round profiles, in which the metallic product produced is immediately processed further in the hot process.

In an advantageous development of the invention, it can be provided for step (b2) that the virtual casting speed is reduced by a fixed amount, which is dependent on a maximum possible casting speed, compared to the actually set casting speed (v _current ). In this case, the virtual casting speed can preferably be reduced by the amount of 0.1 m/min. In any case, this ensures that the cooling capacity of the secondary cooling system is reduced by an admissible amount, as a result of which a greater heat content is achieved for the cast strand. As a result, the position of the sump tip shifts within the predetermined permissible range in the direction of the hot-critical range, but without leaving the predetermined permissible range.

In an advantageous development of the invention, when carrying out step (b2) it can be provided that the predetermined second time (t _v2 ) is at least 200 seconds, preferably at least 250 seconds, more preferably at least 300 seconds, more preferably more than 300 seconds. This means that the virtual casting speed is changed or reduced only at intervals or time steps that are defined by the predetermined second time. Step (b2) is expediently only carried out as long as the position of the sump tip is in a defined section of the predetermined permissible range, with this defined section - viewed in the conveying direction of the cast strand - being between 60% and 90%, preferably 75% % of the length of the predetermined allowable range.

In an advantageous development of the invention, it can be provided that steps (a), (b1) and/or (b2) are carried out fully automatically by the control or regulation unit 17 . This has the advantage that the cooling capacity of the secondary cooling can be changed, namely by controlling the secondary cooling with the water values of the spray plan, taking into account the virtual casting speed formed according to the invention, without the intervention of an operator, for example in the control station of a continuous casting plant. As already explained above, the changed activation of the secondary cooling takes place solely taking into account the virtual casting speed, with a casting speed for the cast strand remaining unchanged.

In an advantageous development of the invention, it is provided that the control or regulation unit of the continuous casting plant is equipped with a process computer, the process computer comprising at least first software that calculates in real time and regulates the casting process. In this case, the process computer is also equipped with second additional software that calculates faster than in real time, so that the calculation speed for the second software is greater than for the first software. The checking or calculation in steps (a), (b1) and/or (b2) of the method according to the invention is carried out using the second additional software, the result of which is then transferred to the first software.

For a method according to the present invention, it is also important that a temperature field is determined, preferably calculated, for the cast strand along its conveying direction within the supporting strand guide, so that the associated temperature is known for each calculated nodal point of the cast strand, namely at a specific point of the cast strand or the plant length, particularly within the supporting strand guide and its cooling segments. An exact position of the sump tip for the cast strand can then be determined from this. In this regard, it is pointed out that such a determination or calculation of the temperature field is expediently carried out using the second software, with the results of this determination or calculation then being transferred from the second software to the first software for the purpose of regulating the casting process and in particular another of controlling the secondary cooling of the supporting strand guide.

• - Es ist möglich, dass die Stranggießanlage weiterhin mit bekannten Spritzplänen betrieben wird.
• - Die Wasserverteilung zwischen Strangmitte und Kanten bleibt erhalten.
• - Eine Änderung der virtuellen Gießgeschwindigkeit ändert direkt die Wassermengen innerhalb der Sekundärkühlung, wodurch diese Regelung schneller und direkter arbeitet als eine herkömmliche ASC-Regelung, die beispielsweise aus DE 10 2018 215 583 A1 bekannt ist.
• - Ein Betreiber einer Stranggießanlage hat mit einer virtuellen Gießgeschwindigkeit ein besseres Verständnis über die Wasseränderung als bei einem Reduktionsfaktor.
• - Es ist möglich, den Energiegehalt eines Gießstrangs signifikant zu erhöhen, so dass die Durchschnittstemperatur am Ofeneinlauf um bis zu 50°C ansteigt.
• - Für die Sekundärkühlung einer Stranggießanlage wird insgesamt weniger Spritzwasser benötigt.
• - Falls sich die Position der Sumpfspitze des Gießstrangs im Sicherheitsbereich der stützenden Strangführung einer Stranggießanlage befinden sollte, wird durch eine starke Erhöhung der Spritzwassermengen die Gefahr vermindert, dass die Sumpfspitze aus der stützenden Strangführung herauslaufen kann. Hierdurch wird die Gefahr einer sogenannten „Walbildung“ zumindest vermindert oder gar ausgeschlossen.

Further advantages of a method according to the invention for controlling or regulating the temperature of a cast strand in a continuous casting plant consist of the following aspects:

• - It is possible that the continuous caster will continue to operate with known spray schedules.
• - The water distribution between the center of the strand and the edges is retained.
• - A change in the virtual pouring speed directly changes the water quantities within the secondary cooling, which means that this control works faster and more directly than a conventional ASC control, which, for example, from DE 10 2018 215 583 A1 is known.
• - An operator of a continuous caster has a better understanding of the water change with a virtual casting speed than with a reduction factor.
• - It is possible to increase the energy content of a cast strand significantly, so that the average temperature at the furnace inlet increases by up to 50°C.
• - Less spray water is required overall for the secondary cooling of a continuous casting plant.
• - If the position of the sump tip of the cast strand is in the safety area of the supporting strand guide of a continuous caster, the risk of the sump tip running out of the supporting strand guide is reduced by a large increase in the amount of spray water. This at least reduces or even eliminates the risk of so-called “whale formation”.

• 1 eine schematisch vereinfachte Seitenansicht einer Stranggießanlage, mit der ein Verfahren nach der vorliegenden Erfindung durchführbar ist,
• 2 ein prinzipielles Schaltschema für ein erfindungsgemäßen Verfahren,
• 3 eine tabellarische Darstellung eines möglichen Spritzplans für die Stranggießanlage von 1, auf Grundlage dessen ein erfindungsgemäßes Verfahren durchgeführt wird,
• 4 ein Diagramm für die Sumpflänge als Funktion der Zeit,
• 5 ein Beispiel für Parameter eines Stranggießprozess zur Durchführung eines erfindungsgemäßen Verfahrens, und
• 6a, 6b ein Flussdiagramm zur Veranschaulichung einer Schrittabfolge eines Verfahrens nach der vorliegenden Erfindung.

Exemplary embodiments of the invention are described in detail below using a schematically simplified drawing. Show it:

• 1 a schematically simplified side view of a continuous casting installation with which a method according to the present invention can be carried out,
• 2 a basic circuit diagram for a method according to the invention,
• 3 a tabular representation of a possible spray plan for the continuous casting plant 1 , on the basis of which a method according to the invention is carried out,
• 4 a plot of swamp length as a function of time,
• 5 an example of parameters of a continuous casting process for carrying out a method according to the invention, and
• 6a , 6b a flow chart illustrating a sequence of steps of a method according to the present invention.

Below are with reference to the 1 until 6 preferred embodiments for a method according to the invention explained, which is used to control or regulate the temperature of a cast strand 10 in a continuous casting plant 12. The same features in the drawing are each provided with the same reference symbols. At this point it is pointed out separately that the drawing is merely simplified and in particular is not shown to scale.

In the 1 is a continuous casting plant 12, with which a method according to the invention can be carried out, is shown in a schematically simplified side view. The continuous casting plant 12 includes a mold 14 which has a vertical outlet downwards. Liquid metal is poured into the mold 14, with a cast strand 10 then exiting the mold 14 downwards.

The continuous casting installation 12 comprises a supporting strand guide 16 along which the cast strand 10 is moved or transported in a conveying direction F. The supporting strand guide 16 can be divided into individual segments, as shown in FIG 1 indicated by the numbers 1-7. Here, the segments 1-4 are designed as cooling segments and combined to form a secondary cooling system, in which the cast strand 10 is exposed to a cooling medium, in particular in the form of water, from both sides through spray nozzles (not shown) and is thus specifically cooled.

The supporting strand guide 16 is - seen in the conveying direction F of the cast strand 10 - the mold 14 immediately downstream or arranged downstream thereof. Correspondingly, the cast strand 10 enters the downstream supporting strand guide 16 immediately after it has exited the mold 14 downwards.

The continuous casting plant 12 can be designed as a vertical bending plant. In this case, the cast strand 10 occurs - as in the 1 shown and explained - first vertically or vertically downwards from the mold 14. The cast strand 10 is bent horizontally only after it has completely solidified, when it (=the cast strand 10) has left the secondary cooling of the supporting strand guide 16 .

In each of the four cooling segments 1-4 of the supporting strand guide 16, the water quantities of the secondary cooling are adjusted or regulated in such a way that the temperatures on the surfaces of the ends of the cooling segments 1-4 of the cast strand 10 meet the target specifications in relation to a position of the sump tip in a predetermined permissible range of the supporting strand guide. This is explained separately below.

The continuous casting plant 12 also includes a control or regulation unit 17, which is connected via a signal path 20 (in 1 simplified symbolized by a dotted line 20) signaling with the secondary cooling, ie with the cooling segments 1-4 is connected. This signal path 20 can be wired or wireless, for example by a radio link or the like.

The control or regulation unit 17 is equipped with a memory 18 in which the necessary process data for the continuous casting plant 12 are stored. To this extent, this memory 18 forms a database. Via an interface (not shown), it is possible to enter or read in this memory 18 individual process data for the continuous casting process that is carried out with the continuous casting installation 12 .

The control or regulation unit 17 includes a process computer 19. First software I can be set up on this process computer 19, with the casting operation of the continuous casting plant 12 running and being controlled or regulated by the first software I.

It is optionally possible for the process computer 19 to set up a second additional software II in addition to the first software I. While the casting operation of the continuous casting plant 12 is running and is being controlled by the first software I, the second software II runs permanently in the background. In this regard, it is separately emphasized that the second software II calculates much faster than in real time, at least faster than the first software I. In other words, the calculation speed for the second software II is set higher than for the first software I.

The meaning and functionality of these two software packages I, II is explained separately below.

In the course of the continuous casting process with the continuous casting plant 12 according to 1 is performed, it is important that the position of a sump tip SP of the cast strand 10 is within a predetermined allowable range B inside the supporting strand guide 16.

• - K: kaltkritischer Bereich;
• - B: vorbestimmter zulässiger Bereich;
• - W: warmkritischer Bereich;
• - S: Sicherheitsbereich.

In the representation of 2 are as a function of the plant length of the continuous casting plant 12 or the length of the supporting strand guide 16 different areas of just this supporting strand guide 16 shown symbolically and provided with different letters. Here mean:

• - K: cold-critical area;
• - B: predetermined allowable range;
• - W: warm-critical area;
• - S: security area.

The arrow symbols, which are placed above the areas K and W and each have the designations "Reduce cooling" or "Increase cooling", are used in the 2 makes it clear that the cooling capacity of the secondary cooling is changed as mentioned if the position of the sump tip SP of the cast strand 10 should be in the cold-critical area K or in the warm-critical area W of the supporting strand guide 16.

The following explains how, in a method according to the present invention, the above-mentioned change in the cooling capacity in the secondary cooling can be carried out in order to thereby shift the position of the sump tip SP of the cast strand 10 back into the predetermined allowable range B or hold it to achieve the position of the sump tip SP in this area B.

During normal operation of the continuous casting plant 12, a spray schedule can be used to control the secondary cooling, an example of which is given in 3 is shown. From this it can be seen that different amounts of cooling water are defined for different casting speeds. This is reflected in the individual columns, which for the example shown are from 3 with values from 0 m/min to 7 m/min. With regard to the individual lines 1-14 is for the spray plan from 3 to understand that these can be individual control loops of (not shown) spray nozzles, which are assigned, for example, to one of the segments 1-4 of the secondary cooling.

The secondary cooling and the associated spray nozzles of the respective cooling segments 1-4 are controlled by the control or regulation unit 17, namely by means of the first software I, with which the processor 19 is equipped.

Regarding a spray schedule for example as in 3 shown, it goes without saying that the water quantities specified here are stored in the memory 18 of the control or regulation unit 17 .

Furthermore, it goes without saying that for different materials to be cast, from which the cast strand 10 can be produced by means of the continuous casting plant 12, different injection plans can also be stored in the memory 18.

• Währenddessen der Gießstrang 10 nach dem Austreten aus der Kokille 14 durch die stützende Strangführung 16 geführt wird und dabei die Oberflächen des Gießstrangs durch ein Ausbringen von Kühlflüssigkeit vorzugsweise in Form von Wasser im Bereich der Sekundärkühlung gekühlt werden, wird in einem Schritt (a) überprüft, ob die Position der Sumpfspitze SP des Gießstrangs 10 in dem vorbestimmten zulässigen Bereich B innerhalb der stützenden Strangführung 16 liegt. Falls dies nicht der Fall sein sollte, wird in einem anschließenden Schritt (b1) die Kühlleistung der Sekundärkühlung in Abhängigkeit von der jeweiligen Position der Sumpfspitze SP des Gießstrangs gezielt geändert. Im Einzelnen werden hierbei folgende Maßnahmen vorgenommen:
  • - Falls die Position der Sumpfspitze SP des Gießstrangs 10 außerhalb des vorbestimmten zulässigen Bereichs und stattdessen in dem warmkritischen Bereich W der stützenden Strangführung 16 liegt, wird die Kühlleistung der Sekundärkühlung erhöht, indem eine virtuelle Gießgeschwindigkeit größer als die tatsächlich eingestellte Gießgeschwindigkeit v_aktuell gebildet wird. Eine solche Erhöhung der Kühlleistung ist in der 2 durch den entsprechenden Pfeil symbolisiert, der von dem warm kritischen Bereich W in den vorbestimmten zulässigen Bereich B hinein weist. Auf Grundlage dessen erfolgt dann die Ansteuerung der Sekundärkühlung mit den Wasserwerten des Spritzplans unter Berücksichtigung dieser gebildeten virtuellen Gießgeschwindigkeit. In Folge dessen wandert dann die Position der Sumpfspitze SP des Gießstrangs 10 von dem warmkritischen Bereich W zurück in den vorbestimmten zulässigen Bereich B, was in der 2 durch einen entsprechenden und nach links weisenden Blockpfeil mit der Bezeichnung „SP“ kenntlich gemacht ist.
  • - Und anderenfalls, nämlich wenn die Position der Sumpfspitze SP außerhalb des vorbestimmten zulässigen Bereichs B und stattdessen in dem kaltkritischen Bereich K der stützenden Strangführung 16 liegen sollte: Dann wird die Kühlleistung der Sekundärkühlung reduziert, indem eine virtuelle Gießgeschwindigkeit kleiner ist als die tatsächlich eingestellte Gießgeschwindigkeit v_aktuell gebildet wird. Eine solche Verminderung bzw. Reduzierung der Kühlleistung ist in der 2 durch den entsprechenden Pfeil symbolisiert, der von dem kaltkritischen Bereich K in den vorbestimmten zulässigen Bereich B hinein weist. Hierbei erfolgt dann eine Ansteuerung der Sekundärkühlung mit den Wasserwerten des Spritzplans unter Berücksichtigung dieser virtuellen Gießgeschwindigkeit. In Reaktion auf diese Reduzierung der Kühlleistung wandert dann die Position der Sumpfspitze SP des Gießstrangs 10 von dem kaltkritischen Bereich K zurück in den vorbestimmten zulässigen Bereich B, was in der 2 durch einen entsprechenden und nach rechts weisenden Blockpfeil mit der Bezeichnung „SP“ kenntlich gemacht ist.

A first embodiment of a method according to the present invention now works as follows:

• While the cast strand 10 is guided through the supporting strand guide 16 after emerging from the mold 14 and the surfaces of the cast strand are thereby cooled by dispensing cooling liquid, preferably in the form of water, in the area of the secondary cooling, it is checked in step (a) whether the position of the sump tip SP of the cast strand 10 is within the predetermined allowable range B within the supporting strand guide 16. If this is not the case, in a subsequent step (b1) the cooling capacity of the secondary cooling system is changed in a targeted manner depending on the respective position of the sump tip SP of the cast strand. In detail, the following measures are taken:
  • - If the position of the sump tip SP of the cast strand 10 is outside the predetermined permissible range and instead is in the hot-critical range W of the supporting strand guide 16, the cooling capacity of the secondary cooling is increased by a virtual casting speed that is greater than the actually set casting speed v _currently formed. Such an increase in cooling capacity is in the 2 symbolized by the corresponding arrow pointing from the warm critical area W into the predetermined permissible area B. On the basis of this, the secondary cooling is then controlled with the water values of the spray plan, taking into account this virtual casting speed that has been formed. As a result, the position of the sump tip SP of the cast strand 10 then migrates from the hot-critical range W back to the predetermined allowable range B, which is shown in FIG 2 is identified by a corresponding and left-pointing block arrow labeled "SP".
  • - And otherwise, namely if the position of the sump tip SP should be outside of the predetermined permissible range B and instead in the cold-critical range K of the supporting strand guide 16: Then the cooling capacity of the secondary cooling is reduced by a virtual casting speed being smaller than the actually set casting speed v is _currently formed. Such a reduction or reduction in cooling capacity is in the 2 symbolized by the corresponding arrow, which points from the cold-critical area K into the predetermined permissible area B. The secondary cooling is then controlled with the water values of the spray plan, taking this virtual casting speed into account. In response to this reduction in the cooling capacity, the position of the sump tip SP of the cast strand 10 then moves back from the cold-critical range K to the predetermined permissible range B, which is shown in FIG 2 is identified by a corresponding and right-pointing block arrow labeled "SP".

As already explained elsewhere above, a virtual casting speed can be formed in such a way that a value for the actually set casting speed v _currently is either increased or decreased by a fixed amount, or in relation to two constant values for the casting speed , which are known from the spray plan, a preferably linear interpolation is carried out. In any case, the secondary cooling and the associated spray nozzles of the respective cooling segments 1-4 of the supporting strand guide 16 are then controlled with the water values of the spray plan, taking into account the virtual casting speed formed according to the invention.

Steps (a) and (b1) mentioned above are expediently carried out repeatedly after a predetermined first time t _v1 has elapsed. In this case, the predetermined first time t _v1 is determined from the quotient of the length of the supporting strand guide 16 and the actually set casting speed v _actual . The following example: If the casting speed is 5 m/min, the cast strand 10 requires 96 seconds (= 8 m / 5 (m/ min) = 1.6 min = 96 seconds). In this case, steps (a) and (b1) would be repeated every 96 seconds.

A second embodiment of a method according to the present invention provides that in step (a) it is checked whether the position of the sump tip SP of the cast strand 10 is within the predetermined allowable range B within the supporting strand guide 16 . Subsequently, in a step (b2), the cooling capacity of the secondary cooling is reduced if the position of the sump tip SP of the cast strand 10 is in the predetermined allowable range B of the supporting Strand guide 16 is located and has not changed within a predetermined second time t _v2 . Such a reduction in the cooling capacity is achieved in such a way that a virtual pouring speed lower than the actually set pouring speed v _currently is formed, with the secondary cooling being controlled with the water values of the spray plan, taking this virtual pouring speed into account.

With regard to the predetermined second time t _v2 , it is pointed out once again at this point that this time can be at least 200 seconds or possibly even longer. On the one hand, this means that in step (b2) the virtual casting speed is only reduced in relatively large time steps, depending on the above-mentioned condition, and as a result the process values for the water quantities for the secondary cooling and the resulting cooling capacity are not changed at intervals that are too short. Furthermore, this ensures that the energy content for the cast strand 10 is then shifted within this predetermined permissible range in the direction of the hot-critical range W, subject to the proviso that the position of the sump tip SP of the cast strand 10 always remains within the predetermined permissible range B . In other words, this increases the sump length for the cast strand 10 .

The successive lengthening of the sump length, which is achieved in the course of step (b2) as explained above, is shown in the diagram of FIG 4 shown symbolically as a function of a distance from the meniscus. As can be seen, there is an increasing step function for the length of the sump, which results from the continuous reduction in the cooling capacity for the secondary cooling.

• - Blauer Bereich (zu kalt) = kaltkritischer Bereich K
• - grüner Bereich (Zielbereich) = vorbestimmter zulässige Bereich B
• - gelber Bereich (zu warm) = warm kritischer Bereich W
• - rote Bereich = Sicherheitsbereich.

The concordance of in the 4 mentioned areas compared to the areas of 2 is to be understood as follows:

• - Blue area (too cold) = cold-critical area K
• - green area (target area) = predetermined permissible area B
• - yellow area (too warm) = warm critical area W
• - red area = security area.

With regard to step (b2), which is part of the method according to the invention according to the second embodiment, it is pointed out separately at this point that this step (b2) can also be provided for the method according to the invention according to the first embodiment, namely subsequently to step (b1). In this respect, it is understood that with such a modification of the method according to the invention according to the first embodiment, steps (a) and (b1) are first carried out, as explained above and in FIG 2 illustrated, after which step (b2) is then carried out, as explained above for the second embodiment and in FIG 4 is illustrated.

The formation of a virtual casting speed in step (b2) can be achieved in the same way as explained above in step (b1) of the first embodiment of the method according to the invention, namely by changing (=increasing or reducing) the actually set casting speed v _current by a fixed amount or by a preferably linear interpolation between two constant values for the casting speed, which are known from the spray plan.

With regard to step (b2), in which the cooling capacity for the secondary cooling is reduced under the existence of the condition mentioned for this purpose, it is pointed out separately that the virtual casting speed compared to the actually set casting speed v _currently by the amount of 0.1 m/min can be reduced.

In connection with step (b2), which is carried out as explained in the second embodiment of the method according to the invention or can be carried out in a modified form of the first embodiment, it is additionally pointed out that this step (b2) is only carried out as long as the position of the sump tip SP is within a defined portion of the predetermined allowable range B. It can be provided that this defined section of the predetermined area B, viewed in the conveying direction F of the cast strand 10, can be determined as 75% of the length of the predetermined permissible area. This example measure of 75% is both in the representation of 2 indicated below the region B as well as in the diagram of FIG 4 indicated as a threshold value for the sump length. As an alternative to this - not shown - this defined section of the predetermined area B can also be defined in that it - seen in the conveying direction (F) of the cast strand (10) - is between 60% and 90% of the length of the predetermined permissible area (B ) definitely.

With regard to a further example of an embodiment of a method according to the present invention, reference is made to the presentation of FIG 5 referenced, where example values for the parameters are listed are listed with which the procedure can be carried out. In this example, the term "target area" means the previously mentioned and explained predetermined allowable area B of the supporting strand guide 16 .

A further example for carrying out a method according to the invention for controlling or regulating the temperature of a cast strand in a continuous casting installation 12 is shown in the flowchart in FIG 6a and 6b called. The abbreviations used herein ZB1, ZB2, ZBPos, dVmaxAll, dVmax1, dVmax2, dVmax3, dV, dVred, dVgreen, t _v1 and t _v2 can be explained from the example of 5 .

With regard to all of the above-mentioned embodiments of a method according to the present invention, it is understood that the checking or calculation in steps (a), (b1) and / or (b2), in particular the formation of a virtual casting speed and the resulting resulting values for a changed activation of the secondary cooling, can take place by means of the second software II and the result of this is transferred to the first software I, for the purpose of a changed activation of the respective spray nozzles in the area of the secondary cooling with regard to the amount of cooling liquid or cooling water. As an alternative to this, it is also possible according to the present invention--as already explained--for only the first software I to be set up on the process computer 19, so that the said steps of a method according to the invention are only carried out using the first software I.

If the amount of spray water is reduced too much, the growth of the strand shell slows down, which can lead to undesired bulging between the support rollers (= bulging). This occurs preferentially in the first segments of the supporting strand guide. To counteract this, a maximum possible reduction "dVmaxAll" (cf. also the specification in the example from 5 ) are given, with the relationship: $${\text{V}}_{\text{current}}-{\text{V}}_{\text{virtual}}<=\text{dVmaxAll}$$

mit i=1,2,3.In addition or as an alternative, a separate maximum reduction in the respective cooling zones (dVmax1, dVmax2, dVmax3) of the secondary cooling can be specified for the first cooling zone, with the relationship: $${\text{dVmax}}_{\text{i}}<\text{dVmaxAll},$$

with i=1,2,3.

Reference List

1-7

(supporting strand guide 16 segments)

10

casting strand

12

continuous caster

14

mold

16

supporting strand guide (of continuous caster 12)

17

control or regulation unit

18

Memory (of the control or regulation unit 17)

19

process computer

20

signal path

B

predetermined allowable area (within the supporting strand guide 16, also referred to as "target area", cf. 5 )

f

Conveying direction (for the casting strand 10)

I

first software

II

second software

K

cold-critical area (within the supporting strand guide 16)

SP

Position of sump tip (of casting strand 10)

S

security area

TV1

predetermined first time

TV2

predetermined second time

tactual

Current or actually set pouring speed

W

heat-critical area (within the supporting strand guide 16)

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018215583 A1 [0027]

Claims (15)

Method for controlling or regulating the temperature of a cast strand (10) in a continuous casting plant (12), wherein the cast strand (10) after continuously emerging from a mold (14) is guided by a supporting strand guide (16) of the continuous casting plant (12) which is at least has a segment (1, 2, 3, 4) with secondary cooling, is guided along a conveying direction (F), the secondary cooling being set by a control or regulation unit (17) and the surfaces of the cast strand (10) being cooled as a result , wherein a temperature field is calculated for the cast strand along its conveying direction (F) within the supporting strand guide and a position of the sump tip (SP) of the cast strand (10) is determined therefrom, wherein in a memory (18) of the control or regulation unit (17) for a material of the cast strand (10) to be cast, a spray plan with water quantities for various control circuits of the secondary cooling, which is applied to the surface of the cast strand are stored, characterized by (a) checking whether the position of the sump tip (SP) of the cast strand (10) is within a predetermined allowable range (B) within the supporting strand guide (16), and (b1) if the position of the Sump tip (SP) of the cast strand (10) is outside the predetermined permissible range and instead lies in a warm-critical range (W) of the supporting strand guide (16): Increase in the cooling capacity of the secondary cooling system by using a virtual casting speed that is greater than the casting speed that is actually set (v _current ) is formed, whereby the secondary cooling is controlled with the water values of the spray plan taking this virtual casting speed into account, or: If the position of the sump tip is outside the predetermined permissible range (B) and instead in a cold-critical range (K) of the supporting strand guide (16 ) is: Reduction of the cooling capacity of the secondary cooling by a e virtual pouring speed is lower than the actually set pouring speed (v _current ) is formed, with the secondary cooling being controlled with the water values of the spray plan, taking this virtual pouring speed into account. procedure after claim 1 , characterized in that the virtual casting speed compared to the actually set casting speed (v _current ) by a fixed amount that depends on a maximum possible casting speed, and depending on the position of the sump tip (SP) in the hot-critical range (W) or is increased or decreased in the cold-critical range (K), preferably that the virtual casting speed is changed by at least 0.2 m/min at a maximum casting speed of 6 m/min. procedure after claim 1 or 2 , characterized in that if it should be determined in step (b1) that the sump tip of the cast strand (10) is in a safety range (S) of the warm-critical range (W), then the virtual casting speed by a fixed amount, which is from a maximum possible casting speed is dependent, is increased, preferably that the virtual casting speed is increased by at least 0.5 m / min. Procedure according to one of Claims 1 until 3 , characterized in that if the position of the sump tip (SP) should be in the cold-critical area (K) of the supporting strand guide (16) and is at a distance of 2 meters or more from the predetermined permissible area (B): reducing the virtual Casting speed is increased by a fixed amount, which depends on a maximum possible casting speed, in order to thereby achieve a reduction in the cooling capacity for the secondary cooling, preferably that the virtual casting speed is increased by at least 0.5 m/min. Procedure according to one of Claims 1 until 3 , characterized in that if the position of the sump tip (SP) should be in the cold-critical area (K) of the supporting strand guide (16) and is at a distance of between 1 meter and 2 meters from the predetermined permissible area (B): reducing the virtual casting speed by a fixed amount that depends on a maximum possible casting speed, in order to thereby achieve a reduction in the cooling capacity for the secondary cooling, preferably that the virtual casting speed is reduced by at least 0.4 m/min. Procedure according to one of Claims 1 until 3 , characterized in that if the position of the sump tip (SP) should be in the cold-critical area (K) of the supporting strand guide (16) and is at a distance of between 0.5 meters and 1 meter from the predetermined permissible area (B): Reducing the virtual casting speed by a fixed amount, which depends on a maximum possible casting speed, in order to thereby achieve a reduction in the cooling capacity for the secondary cooling, preferably that the virtual casting speed is reduced by at least 0.3 m/min. Method according to one of the preceding claims, characterized in that the Steps (a) and (b1) are carried out repeatedly after a predetermined first time (t _v1 ) has elapsed, the predetermined first time (t _v1 ) being determined from the quotient of the length of the supporting strand guide (16) and the actually set casting speed ( v _current ). Method according to one of the preceding claims, characterized in that after step (b1) the following step is carried out: (b2) if the position of the sump tip (SP) of the cast strand (10) is in the predetermined permissible range (B) of the supporting The strand guide (16) is located and has not changed within a predetermined second time (t _v2 ): Reducing the cooling capacity of the secondary cooling system by creating a virtual casting speed that is lower than the actually set casting speed (v _current ), whereby the secondary cooling system is controlled with the water values of the spray plan taking into account this virtual pouring speed. Method for controlling or regulating the temperature of a cast strand (10) in a continuous casting plant (12), wherein the cast strand (10) after continuously emerging from a mold (14) is guided by a supporting strand guide (16) of the continuous casting plant (12) which is at least has a segment (1, 2, 3, 4) with secondary cooling, is guided along a conveying direction (F), the secondary cooling being set by a control or regulation unit (17) and the surfaces of the cast strand (10) being cooled as a result , wherein a temperature field is calculated for the cast strand (10) along its conveying direction (F) within the supporting strand guide (16) and a position of the sump tip (SP) of the cast strand (10) is determined therefrom, the controller storing in a memory (18). - Or control unit (17) for a material to be cast of the cast strand (10) a spray plan with water quantities for different control circuits of the secondary cooling on the surface of the casting trangs (10), characterized by (a) checking whether the position of the sump tip (SP) of the cast strand (10) is within a predetermined allowable range (B) within the supporting strand guide (16), and (b2) if the position of the sump tip (SP) of the cast strand (10) is in the predetermined permissible range (B) of the supporting strand guide (16) and has not changed within a predetermined second time (t _v2 ): reducing the cooling capacity of the secondary cooling, by forming a virtual pouring speed that is lower than the actually set pouring speed (v _current ), the secondary cooling being controlled with the water values of the spray plan, taking this virtual pouring speed into account. procedure after claim 8 or 9 , characterized in that the virtual casting speed is reduced in comparison to the actually set casting speed (v _current ) by a fixed amount that depends on a maximum possible casting speed, preferably that the virtual casting speed is reduced by 0.1 m/min will. Procedure according to one of Claims 8 until 10 , characterized in that the predetermined second time (t _v2 ) is at least 200 seconds, preferably at least 250 seconds, more preferably at least 300 seconds, more preferably more than 300 seconds. Procedure according to one of Claims 8 until 11 , characterized in that step (b2) is only carried out as long as the position of the sump tip (SP) lies in a defined section of the predetermined permissible range (B), preferably that this defined section - in the conveying direction (F) of the Seen cast strand (10) - determined between 60% and 90%, in particular 75% of the length of the predetermined allowable range (B). Method according to one of the preceding claims, characterized in that steps (a), (b1) and/or (b2) are carried out fully automatically by the control or regulation unit (17). Method according to one of the preceding claims, characterized in that the control or regulation unit (17) of the continuous casting installation (12) is equipped with a process computer (19), the process computer (19) comprising at least first software (I) which is Calculates in real time and regulates the casting process, with the process computer (19) including a second additional software (II) that calculates faster than in real time, so that the calculation speed for the second software (II) is greater than for the first software (I ), wherein the checking or calculation in steps (a), (b1) and/or (b2) takes place using the second additional software (II) and the result thereof is then transferred to the first software (I). Method according to one of the preceding claims, characterized in that when the cooling capacity for the secondary cooling is reduced by reducing the virtual casting speed, the virtual casting speed does not fall below a predetermined minimum value, so that the cast strand (10) no bulging occurs in the area or along the supporting strand guide (16) during cooling, taking into account the water values according to the reduced virtual casting speed.

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