EP3944910A1 - Method for producing a cast strand in a continuous casting machine - Google Patents

Abstract

The invention relates to a method for producing a cast strand (100) in a continuous casting plant (110), in which the cast strand (100) after emerging from a mold (112) through a supporting strand guide (116) of the continuous casting plant (110) along a conveying direction (F) is performed. A temperature field is calculated for the cast strand (100) along its conveying direction (F) within the supporting strand guide (116) using a temperature calculation model, and from this a position of the sump tip (PS) of the cast strand (100) within the supporting strand guide (116) is determined. The supporting strand guide (116) has a plurality of segments (S) along the conveying direction (F) of the cast strand (100), each with a number of support rollers (118), with these segments (S) each having an adjustment in the direction of the cast strand (100) takes place in order to achieve a thickness reduction of the cast strand (100). During the production of the cast strand (100), at a first casting speed (v1), the cast strand (100) is approached by a first group (G1) of segments (S), with a solidification portion (FS) of the cast strand (100) at a selected support roller (118) or at a position between two selected support rollers (118) of a certain segment (S) of the first group (G1) assumes a predetermined value.

Description

The invention relates to a method for producing a cast strand in a continuous casting plant according to the preamble of claim 1.

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 guides that support 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 by specifying target temperature curves. The progression of these target temperature curves can vary depending on the material of the material to be cast and, for example, 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 target temperature curve 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) setpoint temperature curves can be run at low casting speeds. Conversely, lower (= colder) setpoint temperature curves should generally be run at higher casting speeds in order to achieve a stronger cooling of the cast strand so that it solidifies within the supporting strand guide.

In continuous casting, a target temperature curve determines the target values for the surface temperature to be reached by the strand within the supporting strand guide, e.g. at the end of individual cooling zones that are part of this supporting strand guide. The amount of spray water from the secondary cooling system is regulated in such a way that these target values are achieved.

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 flow temperature, heat dissipation in the mold, which influences the casting process and thus makes temperature and position control necessary, since there are no stationary conditions.

With increasing slab thickness, the area of central segregation increases, with the number of pores increasing, so that their elimination by soft or hard reduction requires special attention.

In order to achieve maximum production or improved internal quality through soft reduction, position control is advantageous. The secondary cooling and the casting speed are suitable as manipulated variables for position control in continuous casting.

In continuous casting of large slab thicknesses, however, it is problematic to use the secondary cooling water manipulated variable to influence the position of the sump tip of the cast strand in order to keep the sump tip in a defined area of the supporting strand guide. The effectiveness of the secondary cooling decreases with increasing slab thickness. The thicker the strand shell of the cast strand, the greater the energy that has to be dissipated in order for the strand shell to grow. At the same time, this means that the strand surface temperature is lowered. Thus, with the same sump tip position but different cooling intensity, different temperature curves occur over the strand thickness.

According to the prior art, it is also known that slabs with a thickness of 400 mm or more are cast at a casting speed of up to 6 m/min.

A position control in relation to the sump tip of a cast strand by means of secondary cooling has the disadvantage that if there is a major change in the casting temperature, it is necessary to either greatly reduce or greatly increase the amount of water. If the amount of water is greatly reduced, there is a risk of bulging. On the other hand, if the amount of water rises or increases significantly, there is a risk of surface cracks because the surface of the cast strand cools down (too much). A further disadvantage, as a result of the high temperatures and long residence times, is the severe formation of scale, which affects the surface temperature of the cast strand. As a result, a measurement of the surface temperature of the cast strand can be falsified.

Out EP 2 346 631 B1 a method and a device for controlling the solidification of a cast strand in a continuous casting plant when the casting process is started are known. In this case, a continuous casting plant is equipped with a process computer on which first software and second software are installed.

The first software calculates in real time and regulates the casting process, which is carried out with the continuous caster, in a known manner. Using the second software, which has a higher calculation speed than the first software, during the initial phase of a new casting process or when there is a change in the parameters of the currently running casting process, based on processing data currently obtained from the current casting process and/or on the basis of data stored in a database first generates correction factors, with the second software then generating corrected setpoint data for the casting process using these correction factors and transferring them to the first software.

During the continuous casting of metals, Marco segregations, loose cores or blowholes often form in the middle of the strand. As a result, the internal quality of the cast strand is reduced, which in the same way has a disadvantageous effect on the quality of the subsequent metallic products formed therefrom. According to the prior art, it is known to remedy this problem during production by reducing the thickness of the strand, known as soft reduction. This reduction in thickness can take place via a number of segments of the supporting strand guide, these segments preferably being pressed or positioned hydraulically against the cast strand.

The aforesaid reduction in thickness of a cast strand should preferably be within a predetermined range of the solidification fraction of the material of the cast strand, for example between 60% and 85% solidification, which corresponds to a solidification fraction of between 0.6 and 0.85. The selection of the segments of the supporting strand guide, with which the adjustment or pressing against the cast strand is carried out, is based on the position of the calculated sump tip (or the FS portion) of the cast strand.

In continuous casting, the position of the sump tip can shift due to changed process conditions, for example due to overheating, analysis, temperature dissipation in the mold and/or cooling water temperature, even at a constant casting speed and the same amounts of cooling water. This can result in a soft reduction decrease in other segments of the supporting strand guide. The decrease then takes place at other solidification proportions, with the result that the internal quality within the cast strand or within a slab is not constant.

The invention is based on the object of creating a technology for the continuous casting of metals, with which a consistently high quality for metal products that are produced from the cast strand remains guaranteed even when the casting speed changes.

This object is solved by a method having the features of claim 1. Advantageous developments of the invention are defined in the dependent claims.

A method according to the present invention is used for producing a cast strand in a continuous casting installation equipped with a process computer and having at least one casting machine. In this method, the cast strand, after continuously exiting a mold, is guided through a supporting strand guide of the continuous casting plant along a conveying direction, with a temperature field being calculated for the cast strand along its conveying direction within the supporting strand guide using a temperature calculation model, and from this a position of the sump tip of the cast strand is determined within the supporting strand guide. The supporting strand guide has a plurality of identically constructed segments along the conveying direction of the cast strand, each with a number of support rollers, with these identically constructed segments being adjusted in particular hydraulically in the direction of the cast strand, in order to reduce the thickness of the cast strand ( "soft reduction" ). During the production of the cast strand, at a first casting speed, the cast strand is adjusted with a first group of segments, with a solidification portion of the cast strand occurring at a selected support roller or at a position between two selected support rollers of a specific segment of the first group assumes a predetermined value In order to adapt to changed process conditions, the casting speed is adjusted to a changed second value such that the position of the sump tip shifts within the supporting strand guide and thus the contact with the cast strand instead of with the first group of segments a second group of segments takes place, wherein a solidification proportion of the cast strand at a selected support roller or at a position between two selected support rollers of a specific segment of the second group assumes exactly the predetermined value previously determined for d The set first pouring speed has been present at the selected back-up roll or at a position between two selected back-up rolls of the corresponding particular segment of the first group.

In connection with the present invention, an adaptation to changed process conditions of the continuous casting process is achieved by changing the casting speed. During the production of the cast strand, a first casting speed is initially set, at which the adjustment to the cast strand with a first group of segments takes place in the soft reduction zone of the supporting strand guide. Depending on the respective current position of the bottom tip of the cast strand, which in turn depends on the set first casting speed, a predetermined one results for a selected support roller of a specific segment of the first group, or for a position between two selected support rollers of this specific segment of the first group Value for the solidification percentage of the cast strand, namely a value < 1.

The essential finding of the invention is based on the fact that, in order to adapt to changed process conditions, the casting speed is set to a changed second value, namely in such a way that the predetermined value for the solidification proportion, which was previously set at the first casting speed and with a selected support roller of a specific segment of the first group of segments of the supporting strand guide, with which a particularly hydraulic adjustment to the cast strand took place, now with the same selected support roller of a specific segment of the second group of segments, with which a particularly hydraulic adjustment to the cast strand takes place at the changed second casting speed, present. In other words, the position for a predetermined solidification rate of the cast strand within a certain segment of the second group, now that the casting speed has been adjusted to the changed second value, remains unchanged with respect to a selected support roller compared to a certain segment of the first group and the previously set first pouring speed. Thus, when the casting speed changes to the second value in the specific segment of the second group, the predetermined solidification percentage of the cast strand is placed at the same point or support roller as was the case with the previously set first casting speed in the corresponding specific segment of the first group case has been. As a result, with the second group of segments, when the casting speed has been adjusted to the changed second value, with respect to the specific segment of this second group, a soft reduction decrease occurs for the cast strand with the same predetermined solidification rate value as before set first casting speed, with the particular segment of the first group. This ensures that the (internal) quality of the cast strand produced remains consistently high over its length.

In an advantageous further development of the invention, the same is used for the second group of segments with which a particularly hydraulic adjustment to the cast strand takes place at the changed second casting speed Number of segments selected, which has been selected for the first group of segments with which a particularly hydraulic adjustment to the cast strand took place at the first casting speed. The following example: If, at the set first casting speed, there is a particularly hydraulic adjustment to the cast strand with a total of three segments of the supporting strand guide, i.e. the first group of segments consists of these three segments, then at the changed second casting speed there is a particularly hydraulic adjustment carried out on the cast strand also with three segments. Correspondingly, the second group of segments, which is found along the supporting strand guide at a different point than the first group of segments, then contains the same number of segments as the first group, ie three segments in the example mentioned.

At this point it is pointed out separately that it is expedient for the implementation of the method according to the invention that the segments of the supporting strand guide, with which a hydraulic adjustment in particular against the cast strand is possible, are each constructed identically and each have the same number of supporting rollers contain. This ensures that when the casting speed has been adjusted to the changed second value, then, as explained, the predetermined value of the solidification fraction for the cast strand in a certain segment of the second group at the same selected backup roll, or at a position between two selected backup rolls of that segment of the second group, is as in the corresponding particular segment of the first group and at the previously set first pouring speed.

It goes without saying that, deviating from the previously mentioned example of three support rollers per segment, there are also fewer or more than three support rollers in the respective segments of the supporting strand guide, with which a particularly hydraulic adjustment to the cast strand is possible can be, with the proviso that, as explained, these segments are expediently constructed in each case in the same way and contain the same number of support rollers.

In an advantageous development of the invention, if the changed process conditions and the set second casting speed are present, a resulting new position of the sump tip is determined using the temperature calculation model and the temperature field of the cast strand calculated with it, taking into account this new position of the sump tip to carry out the adjustment to the Cast strand a certain other segment within the supporting strand guide is selected in the range of which the new position of the sump tip lies.

In an advantageous development of the invention, a continuous casting plant with which a method according to the invention can be carried out is equipped with a process computer, the process computer comprising at least first software that calculates in real time and regulates the casting process. Furthermore, the process computer includes 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.

At least one value for the changed second casting speed can be calculated by means of the above-mentioned second software, and also on the basis of the temperature calculation model. After this calculation, this second casting speed is expediently transferred from the second software to the first software, so that the actual casting speed in the continuous casting plant corresponds to the calculated second value for the casting speed.

In order to carry out the method according to the invention, it is expedient for the second software to run continuously during the casting process or

makes calculations. In other words, the second software runs permanently in parallel with the actual speed control, which is carried out using the first software. In this way, the effects of disturbance variables such as casting temperature, heat dissipation in the mold and/or changes in the water supply temperatures (e.g. in the secondary cooling or the primary or mold cooling) can be taken into account separately by the second software, and then suitable correction values or calculations in particular for the changed second pouring speed can be transferred to the first software. In this context, it is important that the calculation speed for the second software is selected to be higher than for the first software. After these calculated values have been received by the first software, the first software can regulate or adjust the sump length (i.e. the position of the sump tip of the cast strand) using the calculated second casting speed, which serves as a manipulated variable.

In an advantageous development of the invention, values for the second casting speed can be calculated using the second software and on the basis of the temperature calculation model for all segments of the supporting strand guide, with which a particularly hydraulic adjustment in the direction of the cast strand is possible, such that a solidification proportion of the cast strand at a selected support roller or at a position between two selected support rollers in the individual segments assumes exactly the predetermined value that was previously set for the first casting speed at the selected support roller or at a position between two selected support rollers of the corresponding specific segment of the first group has been present. Subsequently, these values for the second casting speed calculated for the individual segments of the supporting strand guide are compared with a target value for the actual casting speed, with that segment of the supporting strand guide then being selected as the specific segment for the second group of segments, its calculated value for the second pouring speed the Specifications of the target value are met and has the smallest distance to the target value.

In an advantageous development of the invention, the above-mentioned reference value for the casting speed, with which the calculated values for the second casting speed are compared, can be a permissible maximum value for the actual casting speed. In this case, that calculated value for the changed second casting speed is selected that is closest to this maximum value coming from below.

As an alternative to this, the above target value for the casting speed, with which the calculated values for the second casting speed are compared, can also be a permissible minimum value for the actual casting speed. Correspondingly, that calculated value for the changed second casting speed which is closest to this minimum value, coming from above, is then selected for this case.

The selection of the calculated values for the second casting speed explained above ensures that the actual casting speed for the continuous casting process is then adjusted to a value or an "optimal casting speed" which is within the particular segment of the second group of segments , with which a preferably hydraulic adjustment to the cast strand is carried out to reduce the thickness, then the predetermined value for the solidification proportion of the cast strand continues to be at the same point or the selected support roller as before in the corresponding specific segment of the first group at the set first casting speed.

In an advantageous development of the invention, it can be provided that the new position of the sump tip, which results within the supporting strand guide as a function of the casting speed set to the second value, is calculated by the second software and based on the temperature calculation model.

Because the calculation speed for the second software is set higher than for the first software, the method according to the invention makes it possible to look "into the future" with regard to the casting process and its further course. The following example: If the first software, which controls the casting process in real time, has a calculation time of 20 minutes, for example, the same sequence of the casting process can be simulated or calculated using the second software in a much shorter time, e.g. in just 30 seconds . Accordingly, by means of the calculation by the second software, it is possible to gain knowledge about the further course of the casting process at a much earlier point in time compared to the calculation by means of 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.

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 plant with which a method according to the invention can be carried out,

2

a flow chart to illustrate the implementation of a method according to the present invention,

Figures 3, 4

each part of the supporting strand guide a continuous casting of 1 , and

figure 5

Sections of the supporting strand guide of a continuous casting plant from 1 , showing a first and second set of segments of this supporting strand guide.

Below is with reference to the Figures 1 to 5 a method according to the invention is explained, in which a cast strand 100 made of metal is produced in a continuous casting plant 110 by means of continuous casting. 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.

1 shows a basically simplified side view of the continuous casting plant 110 according to the invention.

At this point, it is specifically pointed out that the terms cast strand and metal strand are optionally used as synonyms for the following description.

The continuous caster 110 after 1 comprises a mold 112 having a lower opening 113 and thereby a vertical outlet downwards. Liquid metal, for example steel or a steel alloy, is filled into the mold 112 up to a casting level or bath level 114 .

In the area of a secondary cooling system 130, the continuous casting plant 110 comprises a supporting strand guide 116, which adjoins the lower opening 113 of the mold. Thus, the supporting strand guide 116 is located immediately downstream of the mold 112 . During operation of the continuous caster 110 and when a corresponding method according to the invention is carried out, a cast or metal strand 100 emerges downwards from the lower opening 113 of the mold 112 and is then moved or transported along the supporting strand guide 116 in a conveying direction F.

The supporting strand guide 116 of the continuous casting plant 110 comprises a plurality of segments S, in particular those of identical construction, which are each equipped with adjustable support rollers 118 (cf. also 4 , figure 5 ) are equipped. These support rollers 118 are provided in pairs in each of the segments S in the form of an upper support roller R1 and a lower support roller R2 lying opposite thereto. In the representation of 1 For example, only two such pairs of rollers are each labeled "R1" and "R2".

A so-called soft reduction is possible for the cast strand 100 by means of the individual support rollers R1, R2 and their adjustment in the direction of the cast strand 100 passed between the support rollers 118 in FIG. In this case, both the upper support roller R1 and the lower support roller R2 are expediently engaged, so that a reduction in the thickness of the cast strand 100 is achieved both on its upper side and on its underside. This is particularly advantageous for a metal strand 100 in the form of a slab with a comparatively large cast thickness, i.e. ≥ 250 mm. The internal quality of the cast strand 100 can be improved by the decrease at the top and bottom.

The secondary cooling 130 comprises individual cooling segments (not designated) along the supporting strand guide 116, through which the application of a cooling medium, in particular in the form of water, for example through spray nozzles, is ensured on both sides of the metal strand 100 in order to cool the metal strand 100 in a targeted manner. These cooling segments are each fed with cooling liquid via lines (not shown) and are each equipped with spray nozzles. Accordingly, it is possible through the spray nozzles of each Dispense cooling segments cooling liquid on the surfaces of the metal strand 100, namely on its top and / or bottom.

In the continuous casting plant 110 according to 1 it can be a thick slab plant with which a cast strand 100 with a thickness of preferably 250 mm, or possibly even greater cast thicknesses, can be produced. The continuous casting plant 110 comprises, for example, a total of one hundred and twenty pairs of supporting rollers, which are divided into twenty physical segments or cooling segments 1-20. Here, the crack-critical straightening area is located within the supporting strand guide 116 in the cooling and straightening segments with numbers 8 and 9, which can be equipped with their own control circuits for the coolant supply, so that the specified target temperatures can be achieved.

In the segments S with the numbers 10-20, a targeted reduction in thickness for the cast strand 100 can be carried out, also known as "soft reduction" . Here, these segments S are moved or adjusted with their respectively associated support rollers 118 in the direction of the cast strand 100, preferably hydraulically, in order to achieve a thickness reduction for the cast strand. Correspondingly, the segments S numbered 10-20, with which such an adjustment can be made in the direction of the cast strand 100, form a "soft reduction zone" which is shown in FIG 1 is labeled "111".

With regard to the individual segments of the supporting strand guide 116, it is additionally pointed out that these segments, at least those of the soft reduction zone 11, are expediently of identical construction and each have, for example, four pairs of supporting rollers 118 arranged opposite one another. This number of four support roller pairs 118 is shown in FIG figure 5 as an example for segments no. 11 and no. 17, with the support roller pairs not being shown for the other segments merely for the purpose of a simplified representation.

The continuous casting plant 110 comprises a control or regulation unit 122 which is connected via a signal path 124 to the cooling segments of the supporting strand guide 116, among other things. This signal path 124 can be wired or wireless, e.g. by a radio link or the like.

The control or regulation unit 122 includes a process computer 123 on which a first software I and a second additional software II are set up. The meaning and functionality of these two software packages I, II is explained separately below.

The control or regulation unit 122 is connected to a data memory 126 in which the required process data for the continuous casting plant 110 are stored. To this extent, this data memory 126 forms a database. It is possible to input or read individual process data PD into the data memory 126 via an interface (not shown). This input option is in the 1 symbolized by an arrow with "PD".

The continuous caster 110 is equipped with at least one (unspecified) temperature sensor, or a plurality of such sensors, located adjacent the supporting strand guide 116 . The temperature of the metal strand 100 can be determined by means of such a sensor or a plurality of such sensors in order, for example, to compare the previously calculated temperature of the metal strand 100 with the measurement. The temperature data from the sensor or sensors are first fed to a data acquisition unit 128 and sent from there to the open-loop or closed-loop control unit 122 via the signal path 124 .

Variables or parameters are stored in the data memory 126, on the basis of which setpoint temperatures can be set or specified for the individual cooling segments along the supporting strand guide 116.

These variables can include a first target temperature, a second target temperature and a predetermined distance from the meniscus 114 . These variables depend on a specific material or a specific group of materials from which or which the metal strand 100 is produced, and in any case independently of a specific continuous casting installation.

Based on the parameters mentioned above, which are stored in the data memory 126, the control and regulation unit 122 can be used for the individual cooling segments along the strand guide 116 in the area of the secondary cooling system 130 of a specific continuous casting plant, for example the continuous casting plant 110 of 1 , Target temperatures can be set or specified.

2 shows a flowchart to show the "architecture" of the control or regulation unit 122. Specifically, the process computer 123 (cf. 1 ) of this control or regulation unit 122 has first software I and second software II.

In the diagram of 2 the control or regulation unit 122 is shown placed centrally. The control or regulation unit 122 is set up in terms of programming or has appropriate means to enable data exchange from the second software II to the first software I.

• Werkstoff
• Gießtemperatur
• IST-Wert der Gießgeschwindigkeit
• Sekundärkühlwasser (d.h. Menge und Temperatur)
• Gießlänge.

The control or regulation unit 122 receives the process data or process parameters of the current casting process from the continuous casting plant 110, which is identified by a corresponding arrow pointing from the continuous casting plant 110 in the direction of the control or regulation unit 122. These process parameters include:

• material
• casting temperature
• ACTUAL value of the casting speed
• Secondary cooling water (i.e. volume and temperature)
• casting length.

As explained, these process parameters PD can be entered into the data memory 126 via an interface and from there can reach the processor of the control or regulation unit 122 via the signal path 124 . Following this, this process data is then forwarded by the control or regulation unit 122 both to the first software I and to the second software II.

As indicated by the arrow for "process parameters" pointing to the symbol for the second software II, the second software II also receives information from the control and regulation unit 122 regarding the respective process parameters for the current casting process.

While the casting operation is running and 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.

Regarding the in the 2 mentioned "casting length x" it is pointed out separately that, according to the present invention, the counting of a respective casting length starts in the casting or bath level 114 in each case.

Further aspects that are important for carrying out a method according to the present invention are described below with reference to FIG Figures 3-5 explained.

3 shows in simplified form the segments 10-20 of the supporting strand guide 116, with which the soft reduction zone 11 already mentioned above is formed. For example, the segments 19 and 20 are each denoted by “S” here, which expresses the fact that they are segments of the supporting strand guide 116. This also applies in the same way to segments 10-18, which are not provided with an "S" for the sake of simplicity.

In the example of 3 For example, a first current or actual casting speed v1 can be selected for the production of the metal strand 100, which assumes the value of 1.2 meters/minute. Here, the current sump tip PS of the cast strand 100 may be in the #20 segment of the supporting strand guide 116 . This is in the representations of 3 and 4 symbolized by the designation "PS".

In the production process with the above-mentioned first casting speed v1, a particularly hydraulic adjustment in the direction of the cast strand 100 can take place with a first group G1 of segments, for example with the segments 17-19, as is shown in FIG figure 5 is shown. Correspondingly, for the example discussed here, this first group G1 has three segments with which a soft reduction is carried out. The situation here is such that, for example, in the first segment of this first group _G1 —seen in the conveying direction F—in this case segment no . In the representations of 4 and figure 5 This is symbolized in each case by a corresponding arrow which points to this third supporting roller 118 of segment no. 17, seen in the conveying direction F. Thus, for this example, segment #17 represents a particular segment of the first group G1, and a predetermined value FS ₁ for the solidification fraction is given at a selected support roller 118 of that particular segment of the first group G1.

For operational reasons, for example due to a delay in the steelworks, it may be necessary for the continuous casting installation 110 to reduce the current casting speed, i.e. the first casting speed v1 previously set. The method according to the invention will now be explained using the example of such a reduction in the casting speed.

Using the second software II and on the basis of the temperature calculation model, values for a changed second casting speed v2 are calculated for segments no. 10-20 of the soft reduction zone 111 of the supporting strand guide 116. These values are in the 4 noted above the individual segments, for example v = 0.50 m/min for segment no. 10; v = 0.55 m/min for segment #11; v = 0.61 m/min for segment no. 12, etc..

Then the respectively calculated values for the possible second casting speed v2 are compared with a target value for the actual casting speed. In the present example, this target value is a maximum value which, as in 3 symbolized by an arrow above the supporting strand guide 116, can assume a value of v=0.6 m/min here.

The method according to the invention is now characterized in that the maximum value of 0.6 m/min is not simply set for the required reduction in the actual casting speed, but that the calculated value for the second casting speed v2 is selected which "coming from below " has the smallest distance to this maximum value, ie is closest to this maximum value. For the example explained here, this is the value of v=0.55 m/min, which is assigned to segment no. 11. For the reason that, as explained, the value of v=0.6 m/min for the example given here represents a maximum value that should not be exceeded the value v=0.61 m/min, which is associated with segment no. 12, is also not selected for the second casting speed v2.

In concrete terms, this means that the value of v=0.55 m/min calculated by the second software II is now selected for the changed second casting speed v2, and this value is then transferred from the second software II to the first software I, with with the result that the actual casting speed also assumes this value of the calculated second casting speed v2.

In the example discussed here, the value of v=0.55 m/min for the method according to the invention is to be understood in such a way that within the third group G3 in segment no. whose third supporting roller 118, there is a solidification fraction FS ₂ which corresponds to the predetermined value FS ₁ which was present at the same position of a supporting roller 118 at the previously set first casting speed v1 in segment No. 17 of the first group G1. This is in the figure 5 indicated by a corresponding arrow for FS ₂ pointing to the third support roller 118 of segment #11.

As already explained above, the first group G1 of segments, with which a soft reduction for the cast strand 100 is carried out when the first speed v1 is set, is formed from the three segments Nos. 17-19. In this case, segment no. 17 - seen in conveying direction F - represents the first segment of this group G1.

In order to implement the preferably hydraulic adjustment in the direction of the cast strand 100 with the same number of segments when setting the changed second casting speed v2 within the supporting strand guide 116 as before with the first casting speed v1, for the second group G2 of segments next to the Segment No. 11 also the - in Conveying direction F seen - downstream segments No. 12 and No. 13 selected. Segment no. 11 of the second group G2 now forms a specific segment, namely a first segment of this group G2--seen in the conveying direction F--and thus corresponds to the specific segment of the first group G1, namely segment no. 17.

The selection of the segments no. 11-13 for the second group G2, with which the adjustment in the direction of the cast strand is now carried out with the second casting speed v2 set, is also carried out as a function of a target value, which for the example mentioned in the required reduction for the casting speed must be observed. In any case, by setting the casting speed to the changed second value v2, the position of the sump tip SP shifts within the supporting strand guide 116 and thus the adjustment to the cast strand 100 instead of with the first group G1 of segments with the second group G2 of segments, the solidification fraction FS for the cast strand for a specific segment (for the example under discussion: segment no. 11) of the second group G2 at a selected support roller thereof (for the example under discussion: the third support roller 118, downstream in the conveying direction F seen) assumes exactly the predetermined value that was previously seen in the corresponding specific segment (for the example discussed: segment no. 17) of the first group G1 on its selected support roller (for the example discussed: the third support roller 118, seen downstream in the conveying direction F ) has been present. This is expressed by the relationship FS ₂ = FS ₁ , cf. figure 5 .

The second software II is used to calculate or .simulates what position for a swamp top of the cast strand 100 according to the determined casting length along the supporting strand guide 116 of the continuous casting plant 110 would currently be present.

The actual regulation of the casting process is carried out by the first software I in real time. For this purpose, the first software I receives the necessary information regarding the individual process parameters from the control or regulation unit 122 . Furthermore, the first software I receives via the control or regulation unit 122 also the value calculated by the second software II for the changed second casting speed v2, which is then already a specific segment of the supporting strand guide 116 and a assigned to the second group G2 of segments formed herewith. On the basis of this, the value for an associated setpoint speed (meaning: setpoint casting speed) is then sent back to the control or regulation unit 122 by means of the first software I and is output from there to the relevant components of the continuous casting plant 110 .

This means that the first software I regulates the sump position using the casting speed for the casting process carried out with the continuous casting plant 110 in real time, taking into account the value calculated by the second software II for the changed second casting speed. As a result, it is achieved that even with a change in the casting speed, which, as explained, may be necessary for operational reasons, the soft reduction or the adjustment in the direction of the cast strand with the second group of segments at the second casting speed v2 in In relation to the specific segment of this second group G2, the solidification fraction FS ₂ =FS ₁ is exactly the same as that previously present at the set first casting speed v1 in the corresponding specific segment of the first group G1 at the same position of a support roller 118.

Reference List

1-20

Support roller segments (of the supporting strand guide 116)

100

cast strand/metal strand

110

continuous caster

111

soft reduction zone

112

mold

113

lower opening (of mold 112)

114

Bathroom mirror/casting mirror

116

supporting strand guide

118

Support rollers/pairs of rollers

122

control or regulation unit

123

process computer

124

signal path or signal connection

126

Database or data storage

128

data collection

130

secondary cooling (of continuous caster 110)

I

first software

II

second software

f

Conveying direction (for cast strand 100)

FS

solidification proportion

G1

first group (of segments S)

G2

second group (of segments S)

hp

swamp top

si

Segments (of supporting strand guide 116)

PD

process data

R1

upper support roller(s) 118

R2

lower support roller(s) 118

v1

first casting speed

v2

second casting speed

Claims (10)

Method for producing a cast strand (100) in a continuous casting plant (110), in which the cast strand (100) after continuously emerging from a mold (112) through a supporting strand guide (116) of the continuous casting plant (110) along a conveying direction (F) is guided, wherein a temperature field is calculated for the cast strand (100) along its conveying direction (F) within the supporting strand guide (116) by means of a temperature calculation model and from this a position of the sump tip (PS) of the cast strand (100) within the supporting strand guide (116) is determined wherein the supporting strand guide (116) along the conveying direction (F) of the cast strand (100) has a plurality of identically constructed segments (S), each with a number of support rollers (118), with these identically constructed segments (S) each having a particular hydraulic adjustment in the direction of the cast strand (100) in order to achieve a thickness reduction of the cast strand (100) ( "soft reduction" ), whereby during the production of the cast strand (100) at a first casting speed (v1) the adjustment to the cast strand (100 ) with a first group (G1) of segments (S) and a solidification portion (FS) of the cast strand (100) at a selected support roller (118) or at a position between two selected support rollers (118) of a specific segment (S) the first group (G1) assumes a predetermined value, characterized, that to adapt to changed process conditions, the casting speed is adjusted to a changed second value (v2) such that the position of the sump tip (PS) within the supporting strand guide (116) and thus the cast strand (100) is now positioned on the cast strand (100) instead of with the first group (G1) of segments (S) with a second group (G2) of segments (S), with a solidification portion (FS) of the cast strand (100) at a selected support roller (118) or at a position between two selected support rollers (118) of a specific segment (S) of the second group (G2) assumes exactly the predetermined value previously set for the set first casting speed (v1). of the selected support roller (118) or at a position between two selected support rollers (118) of the corresponding particular segment (S) of the first group (G1). Method according to Claim 1, characterized in that for the second group (G2) of segments (S), with which a particularly hydraulic adjustment to the cast strand (100) takes place at the changed second casting speed (v2), the same number of segments ( S) is selected, which was selected for the first group (G1) of segments (S), with which a particularly hydraulic adjustment to the cast strand (100) at the first casting speed (v1) took place. Method according to Claim 1 or 2, characterized in that if the changed process conditions and the set second casting speed (v2) are present, a resulting new position of the sump tip (PS) is determined using the temperature calculation model and the temperature field of the cast strand (100) calculated with it , taking into account this new position of the sump tip (PS) to carry out the adjustment to the cast strand (100), a certain other segment (S) is selected within the supporting strand guide (116) in the area of which the new position of the sump tip (PS) located. Method according to one of the preceding claims, characterized in that the continuous casting plant (110) is equipped with a process computer (123), the process computer (123) comprising at least one first piece of software (I) which calculates in real time and controls the casting process, wherein the process computer (123) includes 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). Method according to Claim 4, characterized in that at least one value for the changed second casting speed (v2) is calculated by means of the second software (II) and on the basis of the temperature calculation model. Method according to Claim 5, characterized in that the changed second casting speed (v2) is calculated by means of the second software (II) and on the basis of the temperature calculation model and is then transferred to the first software (I), so that the actual casting speed in the continuous casting plant ( 110) corresponds to the calculated second value for the casting speed. Method according to Claim 5 or 6, characterized in that by means of the second software (II) and on the basis of the temperature calculation model for all segments (S) of the supporting strand guide (116) with which a particularly hydraulic adjustment in the direction of the cast strand (100) is possible values for the second casting speed (v2) are calculated in each case in such a way that a solidification proportion (FS) of the cast strand (100) at a selected support roller (118) or at a position between two selected support rollers (118) in the individual segments ( S) each exactly the assumes a predetermined value previously present for the set first casting speed (v1) at the selected support roller (118) or at a position between two selected support rollers (118) of the corresponding particular segment (S) of the first group (G1), wherein then these values for the second casting speed (v2) calculated for the individual segments of the supporting strand guide (116) are compared with a target value (v _target ) for the actual casting speed and then that segment of the supporting strand guide (116) as a specific segment for the second group (G2) of segments (S) is selected whose calculated value for the second casting speed (v2) satisfies the specifications of the target value and has the smallest distance from the target value. Method according to Claim 7, characterized in that the target value (v _target ) is a permissible maximum value for the actual casting speed. Method according to Claim 7, characterized in that the target value (v _target ) is a permissible minimum value for the actual casting speed. Method according to one of Claims 4 to 9, characterized in that the new position of the sump tip (PS), which results within the supporting strand guide (116) as a function of the casting speed set to the second value, is determined by means of the second software (II) and is calculated based on the temperature calculation model.

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