EP2229249B1 - Continuous casting line with a device for determining stiffness states of a casting strand and associated method - Google Patents

Description

Technical area

The invention relates to a method for determining solidification states of a cast strand in a continuous casting plant.

State of the art

Continuous casting plants are well known in the art. Such continuous casting plants for casting liquid metal have, after the mold, typically a support roll stand with strand guide segments for the cast strand. In the strand extrusion lines, the knowledge of the solidification length of the cast strand is of particular importance. The solidification length or the point of complete solidification of the strand is a parameter for operating the continuous casting plant. The point of solidification or the solidification length corresponds to a point with a fixed portion of the cast strand of 100%, which means that in the core of the cast strand no liquid or doughy material is no longer present. Furthermore, the knowledge about the degree of solidification of the strand is less than 100% of interest for strand guidance and strand cooling.

Continuous casting plants are known in the prior art in which the solidification length is achieved by measuring the displaceable amount of the core liquid volume per unit length and building on these measured values Model calculation is performed for the instantaneous length of the sump tip. Such a continuous casting plant is known by the WO 2005/068109 A1 ,

It is, moreover, known that the level of complete solidification is utilized by measuring compressive forces occurring at a plurality of pairs of rolls and comparing them to determine the pair of rolls undergoing the random consolidation, because no further increase in stress occurs. Such a continuous casting is by the DE 25 30 032 known.

Furthermore, the disclosure EP 1 193 007 A1 a method for determining the position of the final solidification in the cast strand, wherein support segments are provided and for determining the position of the final solidification at least in one of the support segments, the pullout tensile force of the tension rollers and / or the clamping force of the hydraulic piston-cylinder units of the support segments is measured and from the Measured values of the area of the sump tip is determined.

Furthermore, it is known that a pyrometer measurement, a bolt-shot method, an inner-crack determination or, as above, a force measurement on lifting cylinders is carried out to determine the strand solidification. However, these methods can only be used temporarily, and they can only be used locally.

Furthermore, there is the possibility of purely arithmetic determination of the position of the stranded solidification, which however requires a separate model for each plant and which must be validated by the measurements cited above. Also, material may vary from material to material, so the model may need to be material dependent.

Presentation of the invention, object, solution, advantages

It is the object of the present invention to provide a method for determining solidification states of the cast strand in a continuous casting plant, in which a reliable and continuous performance of the determination of the solidification states can be carried out.

According to the invention the object is achieved by a method comprising the features of claim 1. According to the invention, this takes place in a continuous casting plant with a device for determining solidification states of the casting strand with a strand guide with continuous casting segments with rollers, in which at least one of the continuous casting segments is designed as a measuring segment, wherein at least one or more measuring points for direct or indirect determination of one or more Roll acting force is provided, further wherein the at least one measuring point is preferably arranged on a bearing block between a bearing and the segment frame of the strand segment and a data processing unit is provided which determines the solidification states of the cast strand based on the data of the at least one measuring point.

According to the invention, at least one of the continuous casting segments is designed as a measuring segment, wherein at least one measuring point or several measuring points for direct or indirect determination of the force acting on one or more rollers is provided, wherein furthermore the at least one measuring point on a bearing block preferably between a bearing and the segment frame the continuous casting segment is arranged which detects a quantity representing a force and a data processing unit is provided which determines the solidification states of the cast strand on the basis of the data of the at least one measuring point.

It is expedient if the measuring point is provided on at least one bearing block of a center bearing or more central bearings. It is also expedient if the measuring point is provided on a bearing block on the fixed side and / or on the loose side of a roller. Also can be advantageous Are provided plurality of measuring points within the strand guide, which are interconnected. In this case, the connection can advantageously be made by the data processing unit to a measuring system.

Furthermore, it is expedient if the center bearings are designed by single or multiple shared roles as measuring points.

Furthermore, it is expedient according to the invention if the data processing unit determines level differences of the measured variable by means of analytical, statistical evaluation methods and derives therefrom a solidification state.

According to the invention, the determination of the solidification state takes place by assigning a solidification state to a characteristic measured variable. In this case, a characteristic measured variable is a bearing force or a bearing deformation. Continue to take place
the determination of the solidification state by assigning a solidification state to a scattering of a characteristic measurand.

According to the invention, a scattering of a characteristic measured variable is the scattering of a bearing force or a bearing deformation.

It is likewise advantageous if the data processing unit evaluates the measured variable by means of fast Fourier analysis or other statistical evaluation methods and thus determines the apparatus influences on the measured variable.

Brief description of the drawings

The invention will be explained in more detail on the basis of an embodiment with reference to the drawings.

Fig. 1

eine schematische Darstellung eines Gießstrangs mit verschiedenen Erstarrungszuständen,

Fig. 2

ein Diagramm,

Fig. 3

eine schematische Darstellung einer Stranggießanlage,

Fig. 4

eine schematische Darstellung eines Lagers,

Show it:

Fig. 1

a schematic representation of a cast strand with different solidification states,

Fig. 2

a diagram,

Fig. 3

a schematic representation of a continuous casting plant,

Fig. 4

a schematic representation of a warehouse,

Preferred embodiment of the invention

The FIG. 1 schematically shows a representation of a cast strand 10 with different solidification states. The casting strand 10 is guided by a plurality of strand guiding elements 1. In this case, the strand guide elements 1 castors 2 rolls, which are mounted by means of roller bearings 3. In the embodiment of FIG. 1 schematically four segments 1 are shown, each having five pairs of rollers 2. The cast strand 10 is guided by the rollers. In a first region I, the cast strand 10 is in a solidification state which has a degree of solidification of less than 20 to 30%. This means that a liquid or doughy fraction 6 of 80 to 70% is present. In a second region II, the Gleßstrang 10 is in a solidification state, which has a solidification degree with a solid content 5 of 20 to 80%. In a third region III, the Gleßstrang 10 is in a solidification state, which has a solidification rate with a solids content of 70 to 80% to less than 100%. In a fourth range, there is correspondingly a solidification state of 100%. The sump tip 4 is thus in the last area IV.

As can be seen, the measured variable representing the roller force, such as a deformation, lies in a central region in the first region. The scatter this measure is at a low level. In area II, both the measured variable and its scattering are at a high level. In area III and area IV, the measured value is at a low level, but the spread of the measured variable is at a medium level.

Region I corresponds to the liquid phase of the strand with a liquid core. As a result, the liquid phase lying at a higher level in the Tell area is burdened by upstream parts of the strand on the strand shell and pushes them from the inside to the outside. This ferrostatic must therefore be absorbed by the bearing forces. The force is increased in comparison to the solidified state, which means that the measured value representing the force is at an average level. The soft strand dampens well so that the standard deviation of the measurand representing the force is small. This first region I ends depending on the steel grade in the range of 20 to 30% solids.

The region II represents a transition region in which the force level or the level of the measured variable representing the force is at a higher level than in the region I. This area has a solidification state of 30 to 70%. The strand 10 also has a liquid core with a solid outer region. In addition to the ferrostatic, a proportion of the strand deformation is added. The attenuation of the strand is lower, so that the variance of the force or the force representing the measured variable than in the area I is.

The region III represents a virtually solidified region, in which the force level or the level of the force representing the measured variable perpendicular to the casting direction is low. In this area III only parts of the weight and pull-out force act. The scattering or the standard deviation is high due to the low attenuation of the quasi-solidified strand. In this state, although still present melt, but separated by bridges and so there is no continuous steel column,

Region IV is the solidified region in which there are substantially the same force and variance ratios as in region III.

The FIG. 2 shows a diagram in which measurement results are shown, which were obtained at a measuring point which is arranged on a segment of a continuous casting plant. In this case, different measuring points are not arranged at different segments in this example, but measuring points are used on a segment and the solidification ranges move through the measuring points. In the present case, two measuring points are arranged on a fixed and a floating bearing of a roller bearing. The FIG. 2 shows in the lower area with the lower two curves the measured values of a measuring gap representing a force. In this case, a change in the signal representing the force can be detected, and as a result an assignment to the status areas I to III can be made, as explained above. The top curve shows the casting speed as a function of time. It can be seen that with changed casting speed, the position of the sump tip or the boundaries between the state areas shifts. At high speed, the state area I with a high liquid content is located at the measuring point. At reduced speed, the status area II with a medium liquid content is located at the measuring point. At low casting speeds, the state area III is located at the measuring point. Thus, it can be seen that with increasing casting speed, the liquid content at the measuring point decreases and there is a change in the state regions at the measuring point.

The FIG. 3 schematically shows a continuous caster 20 with a casting strand 21 and shown with six segments 22 to 27. Preferably, the sump tip would be found in the region of the last or possibly also penultimate segment when the casting speed is high. So it may well happen that at high casting speeds of greater than 6 m / min, such as 7 m / min, the sump tip in the last, sixth segment 27 is located.

Therefore, it is particularly advantageous to measure the solidification conditions as permanently as possible and to be able to determine their distribution or the position of the sump tip. As measuring points, for example, rollers or roller bearings can be selected, with quite a measuring point on a floating bearing and / or on a fixed bearing a role is selectable. By arranging different measuring points on different rollers, preferably in different segments, an advantageous distribution of the solidification states can be detected.

Thus, for example, in the case of a continuous slab caster with a casting speed of 6 to 7 m / min, it can be advantageously achieved permanently that the solidification states can be detected. The sump tip is then, for example, in the sixth segment 26, the hitherto last segment.

To detect the solidification states, a bearing force measurement is performed. The bearing force measurement via an inductive distance measurement, for example in bearing blocks 30, see FIG. 4 , The measuring bearing blocks 30 are slotted horizontally below the bearing shells 33 by means of slot 32 and equipped with an inductive distance sensor 34. The change in the slot height of the slot 34 behaves approximately proportional to the applied force.

The measuring bearings 30 are installed, for example, in the center bearings of long sub-rollers 2 and 7 of the segments 24 and 25 on the fixed side and / or on the Losselte. In this way, the bearing force is determined at 2 x 4 points over the system length.

As the FIG. 4 shows the bearing block 30 of a split Mlttenlagers slotted below the bearing shell, which causes a defined bearing weakening. The position and the geometry of the gap are preferably designed so that at a maximum load advantageous maximum deflection the gap top and no plastic deformation occurs. The distance sensor 34 is inserted centrally from the bearing foot 35 through a bore 36 into the bearing block 30 and protrudes advantageously into the measuring gap 32. The slot 32 is thus designed such that due to the applied force through the cast strand, a local deformation occurs that can be detected. In this regard, let's look at the older one DE 10 2006 027 066 verwlesen. Furthermore, the data processing unit 38 can be seen, which receives data from the sensors (34) of the measuring points and determines the solidification states.

LIST OF REFERENCE NUMBERS

1

Strand guiding element

2

role

3

roller bearing

4

crater tip

5

solid portion

6

liquid fraction

10

cast strand

20

continuous casting plant

21

cast strand

22

segment

23

segment

24

segment

25

segment

26

segment

27

segment

30

bearing block

32

Slot, measuring gap

33

bearings

34

sensor

35

foot

36

drilling

37

Measuring gap top

38

Datenverarbeltungseinhelt

Claims (1)

1. Method of determining states of solidification of the cast strip in a continuous casting plant (20) with a strip guide with cast-strip segments with rollers (2) for guidance of the cast strip, wherein at least one of the cast-strip segments (22, 23, 24, 25, 26, 27) is designed as a measuring segment, wherein at least one measuring point for direct or indirect determination of the force acting on one or more rollers (2) is provided, wherein in addition the at least one measuring point is arranged at a bearing head (30) preferably between a bearing and the segment frame of the cast-strip segment, and a data processing unit is provided, which determines states of solidification of the cast strip on the basis of the data of the at least one measuring point, wherein the measuring point is provided at at least one bearing block (30) of a centre bearing or several centre bearings, wherein the centre bearings of singly or multiply divided rollers (2) are constructed as measuring points, in addition a plurality of measuring points, which are connected together, is provided within the strip guide, wherein the connection by the data processing unit (38) with a measuring system takes place and wherein differences in level of the measurement variables are determinable by means of the data processing unit (38) through analytical, statistical evaluating methods and a state of solidification is derivable therefrom, wherein determination of the state of solidification can be carried out by association of a state of solidification with a variance of the bearing deformation, characterised in that the cast strip guided in the strip guide is divided into four regions I to IV, wherein the first region I represents the liquid phase of the strip with a liquid core, the region II represents a transition region, the third region III represents a quasi-solidified strip and the fourth region IV represents the solidified cast strip, the measurement variable, such as a deformation, representing the roller force in the first region I lies in a median range and the variance of this measurement variable lies at a low level, both the measurement variable and the variance thereof in the second region II lie at a high level and the measurement variable in the third region III and the fourth region IV lie at a low level and the variance of the measurement variable in the third region III and fourth region IV lie at a median level, and wherein the association of the measurement variable and the variance thereof with the first to third regions I to III is carried out in such a manner that a change of the signals representing the force is used.

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