AT506673A1 - Feeding coolant on to strand in continuous casting comprises measuring instantaneous positions of narrow side walls of die and spraying coolant on to it along strand guide at levels corresponding to alterations in e.g. strand breadth - Google Patents

Abstract

Method for feeding coolant on to a strand (2) in continuous casting comprises continuously or discontinuously measuring the instantaneous positions of the narrow side walls (1b) of the casting die (1). Coolant is then sprayed onto the strand as it passes along the strand guide (3), at different levels (H1 - H6) corresponding to alterations in strand breadth and/or position in the casting die. An independent claim is included for plant for carrying out the method with coolant sprays (5) fitted with hydraulic cylinders (8) which control their position and are connected to a control unit fed with data from sensors (1d) which measure the stand breadth or position in the die.

Description

2008P07171

Method for Kühlmittelaufbrinauna on a cast metal strand in a Stranaaießanlaae and Stranaaießanlaae to.

Technical area

The invention relates to a method for targeted cooling of a cast metal strand in a strand guide of a continuous casting and a continuous casting plant which allows targeted cooling in the continuous casting with time-dependent variable casting width.

The invention relates in detail to a method for applying coolant to a cast metal strand in a continuous casting plant, the metal strand being formed in a cooled continuous casting mold with a strand width defined by narrow side walls and the partially solidified metal strand subsequently being passed through a strand guide and cooled continuously in several horizons therein wherein the coolant application in the strand guide is effected as a function of the strand width.

The invention further relates to a continuous casting plant for the continuous production of a metal strand with at least one continuous casting mold for forming a partially solidified metal strand having a defined strand width and strand thickness, the continuous casting mold comprising broad side walls and narrow side walls which can be positioned relative to the latter, and a strand guide arranged downstream of the continuous casting mold for supporting and guiding the strand casting mold Metallstranges, are arranged in the cooling means for applying a coolant to the metal strand in a plurality of horizons and associated with adjusting means for positioning of spray nozzles in dependence on the strand width. • ·

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State of the art

The general design of a continuous casting machine which can be assigned to the prior art is illustrated in FIG. The continuous casting plant shown in a longitudinal section comprises a cooled continuous casting mold 1, with two broad side walls 1a and two narrow side walls 1b, wherein in the continuous casting mold 1, a metal strand 2 is formed, which is then conveyed by a strand guide 3 formed by a roller stand and continuously cooled in it. Between the consecutive in the strand transport direction strand guide rollers 4 spray nozzles 5 are arranged for coolant application in a plurality of horizons H1 to H4, wherein in each horizon a plurality of spray nozzles can be arranged transversely to the strand transport direction side by side, with which coolant distributed over the normal lying to the image plane strand width of the Metal strand is applied. In modern plants, the strand guide is formed by strand guide segments 6 which combine a plurality of successive strand guide rollers in a support frame. Within the segment in the strand conveying direction successive spray nozzles are suitably connected by a common spray bar 7 and jointly adjustable. The common adjusting device 8 is associated with the horizon H5, H6.

Horizon in this document is understood to mean a plane arranged perpendicular to the strand conveying direction or an area in the strand guide in which spray nozzles alone or even groups of spray nozzles can be jointly positioned. Groups of spray nozzles are to be understood in the strand conveying direction successive spray nozzles, which are structurally connected and jointly adjustable. These are assigned to a horizon, although they extend over a length section area of the strand guide in the strand conveying direction.

WO 2007/121804 discloses a spray nozzle adjustment device which can be used for strand guide segments, with which a positioning of the spray nozzles arranged in a horizon can be carried out on a strand width set in the continuous casting plant. Such Spritzdüseverstelleinrichtungen are always based on an axis of symmetry in the strand guide, which also includes the continuous casting mold. A casting width change in the mold is made by ♦

symmetrical adjustment of the narrow side walls of the continuous casting mold relative to this axis of symmetry, so that in the strand guide also only a symmetrical relative to the symmetry axis displacement of the spray nozzles is necessary to ensure a uniform coolant application over the strand width.

AT 500 814 B1 discloses a continuous casting mold adjustable to various casting widths / strand widths with broad side walls and narrow side walls arranged adjustably between them. If strand width changes take place only at large time intervals, localized signs of wear on the broad side walls, which have a negative effect on the surface quality of the cast strand after a strand width increase, occur. To minimize this localized wear, the casting center axis is continuously or discontinuously displaced to itself during casting by sliding the narrow side walls in parallel in the same direction. This has an effect on the time-dependent position of the metal strand in the strand guide and its cooling. In particular, the overmolding of the strand edges of the metal strand leads to unequal cooling conditions and to an increased susceptibility to edge cracks, due to excessive strand edge cooling.

From WO 2005/120746, for example, a continuous casting plant for selectively casting a wide metal strand or two narrower metal strands on the other hand known. When casting two independent strands, the transport also takes place here through the common strand guide under symmetrical conditions to the symmetry axis of the strand guide. Thus, the designed for the casting of a wide metal strand cooling device can be easily used for two equal width, but narrower metal strands. Difficulties in maintaining even cooling conditions in the secondary cooling zone also arise with differently wide strands or with an asymmetrical distribution of the two strands in relation to the axis of symmetry.

Presentation of the invention

The object of the present invention is therefore to avoid the disadvantages of the known prior art and to propose a method for applying coolant to a cast metal strand in the secondary cooling zone of a continuous casting plant and a continuous casting plant with a cooling device in the secondary cooling zone of a strand guide, in which a change in position of the formed Metal strands in the continuous casting mold, a corresponding adaptation of the coolant application is carried out in the strand guide in order to avoid over-spraying of the metal strand edges or an undesirably unequal coolant application and to ensure a largely uniform running strand cooling.

This object is achieved in a method of the type described above in that at a time-varying strand width and / or strand position in the continuous casting mold, the respective instantaneous positions of the narrow side walls are detected continuously or discontinuously and taking into account the casting speed, the coolant application to the metal strand in successive horizons the strand guide takes place in accordance with the changing strand width and / or strand position. The consideration of the casting speed, which can be variable over the casting time due to operation, allows the determination of periods of time that a certain strand element requires until the respective horizons in the strand guide are reached. Thus, the time is determined in which the coolant application must be made on the metal strand in the respective horizon to the changing strand width and / or strand position.

Accordingly, it is advantageous if the transport time of the metal strand from an initial horizon in the continuous casting mold to the respective horizon of the coolant application in the strand guide, which is preferably calculated from the casting speed, is used for the positioning of the spray nozzles of a cooling device in the respective horizons of the strand guide.

So that an adaptation of the coolant application in a horizon of the strand guide can be carried out in a simple manner, it is expedient if the coolant application takes place in a horizon of the strand guide by at least two spray nozzles. Thus, the respective outer spray nozzles can be aligned with the current position of the lateral strand edges and over-spraying or excessive cooling of the strand edges can be avoided.

The coolant application to the metal strand takes place in the same way in the outside of the sheet and in the arc inside of the strand guide, wherein in the description reference is made to only one of these two pages.

According to a specific embodiment of the coolant application to the metal strand, the amount of coolant allocated to the individual spray nozzles is determined as a function of the spray nozzle spacing of the metal strand surface to be cooled or as a function of the spray width swept on the metal strand surface. A change in the distance of a spray nozzle from the metal strand surface leads to an altered specific coolant application to the metal strand and thus to changed cooling conditions compared to another spray nozzle with a different distance to the metal strand surface.

Another possibility for influencing the cooling conditions on the metal strand results when the cooling which has already taken place during the transport time from the starting horizon in the mold to the respective horizon of the coolant application in the strand guide is taken into account in the determination of the amount of coolant still to be applied. Especially with larger casting speed changes, in particular one

Gießgeschwindigkeitsreduzierung during the ongoing casting process can still be intervened during the residence time of the metal strand in the strand guide on the cooling course regulating. Such casting speed changes are regularly made e.g. necessary for a ladle change.

Suitably, the detection of the time-varying strand width and / or strand position in the continuous casting mold and the coolant application to the metal strand in successive horizons of the strand guide according to the changing strand width and / or strand position by the following steps: The time-varying strand width and / or strand position in an initial horizon of the continuous casting mold is detected by position detection or position determining means, said data being measured by a position sensor associated with the narrow side wall of the mold or predetermined by an associated control device or a computing unit. These determined or provided data are processed in a control device or a processing unit and control signals for the • • • • • •! 6Γ · \ ·· ··· · ♦ ·· • · · ·! Time-dependent positioning of the spray nozzles generated in the respective horizons of the strand guide and fed to the adjustment time of transport.

Preferably, the coolant is applied to the metal strand in a horizon of the strand guide by at least two independently positionable spray nozzles, wherein the adjustment of the spray nozzles or a spray nozzle-carrying spray bar by the generatrix of the spray cone of the coolant (in cone jet nozzles) or by the spray angle in the width direction of the coolant ( in flat jet nozzles) is determined.

Furthermore, the object underlying the invention in a continuous casting of the type described above is achieved in that the narrow side walls position detection or position determining means for determining the current strand width and / or the current strand position are assigned in the mold, a control device or a computing unit for recording and Processing of the time-dependent instantaneous values of the strand width and / or strand position and for generating control signals for positioning the spray nozzles of the cooling devices is provided in the individual horizons of the strand guide and are provided in the individual horizons of the strand guide independently controllable adjustment for spray nozzles or spray nozzle groups.

Suitably, the position detection or position determining device for directly or indirectly determining the position of the narrow side wall in the continuous casting mold is formed by a position sensor which is directly or indirectly associated with the narrow side wall. By determining the position of the two narrow side walls of the cast metal strand is clearly defined in its strand width and in its position in the strand guide or with respect to the symmetry axis of the strand guide at any time. Equally, the position determination can also be derived by means of corresponding default values from the plant control system.

The position transmitter is preferably assigned to the narrow-side adjusting device, in particular integrated into the hydraulic adjusting cylinder. In the strand guide, a speed measuring device for detecting the time-dependent casting speed or strand transport speed is provided on at least one, preferably driven strand guide roller.

In order to be able to easily position several adjacent, independently engageable spray nozzles in relation to one another, so that no undesired free space between adjacent spray cones or undesired overlaps on the strand surface occurs, it is advantageous if the independently controllable adjusting devices of the spray nozzles comprise adjusting cylinders that perform a linear adjustment movement allow a spray nozzle in which the direction of movement of the respective spray nozzle or a spray nozzle-carrying spray bar parallel to the generatrix of the spray cone of the coolant jet (cone cone nozzles) or by the spray angle in the width direction of the coolant jet (in flat spray nozzles with elliptical spray pattern) in the associated horizon.

The spray nozzles are assigned coolant supply devices with metering devices for controlled distribution of coolant quantity.

A small number of necessary adjusting devices for the spray nozzles is achieved when a plurality of spray nozzles arranged one behind the other in the strand conveying direction is associated with a common adjusting device in a horizon.

The strand guide is expediently formed by a plurality of strand guide segments, and in each segment at least one common adjusting device in a horizon is assigned to the spray nozzles arranged one behind the other in the strand conveying direction. However, a horizon can also extend over two or more segments or be completely detached from a segment assignment.

Brief description of the drawings

Further advantages and features of the present invention will become apparent from the following description of non-limiting embodiments, reference being made to the following figures, which show:

1 shows a longitudinal section through a continuous casting plant with a schematic representation of the essential system components,

2 shows a plant configuration for the implementation of the method according to the invention in a continuous casting plant according to FIG. 1, FIG.

3 shows the independent coolant supply with a metal strand moved asymmetrically in relation to the plant symmetry axis in the strand guide;

4 shows the independent coolant supply in the case of two metal strands which are moved asymmetrically with respect to the system axis of symmetry in the strand guide.

Embodiment of the invention

Figure 1 shows a plant longitudinal section through a continuous casting plants of conventional design for casting metal strands with slab or thin slab cross-section, as in their basic structure for the implementation of the method for selectively cooling a cast metal strand and with appropriate adaptation of the Strangießkokille for simultaneous casting of two metal strands is suitable.

The continuous casting plant has a continuous casting cocilia 1 with broad side walls 1a and between these wide side walls slidably and clampably arranged narrow side walls 1b. Each of the narrow side walls 1b is connected to a narrow side adjusting device 1c. These narrow-side adjustment allow each other in opposite directions of the narrow side walls to set the strand width B product specific or change. But they also allow a synchronous, continuous or iterative displacement of the narrow side walls to keep the wear on the broad side walls 1a locally low. The adjustment of the narrow side walls takes place with the involvement of position detection or position determining devices 1d, which here comprise a position sensor on each narrow-side adjusting device 1c.

The formed in the continuous casting mold 1 metal strand 2 passes through after its exit from the Strangießkokille the immediately following strand guide 3 (secondary cooling zone), which is formed by a plurality of strand guide rollers 4 and supported in the metal strand, out and is cooled intensively with spray nozzles 5. The strand guide rollers 4 are either arranged in pairs, as shown in the upper part of the strand guide or are summarized in groups in a Trrahähmen and form strand guide segments 6, as shown schematically in the lower part of the strand guide.

Between each other in strand conveying direction S consecutive strand guide rollers 4 in a plane normal to the strand transport direction usually a plurality of spray nozzles 5 are arranged both on the outer bow and the inner arc of the strand guide 3, with which coolant is applied to the broad side walls of the metal strand 2. The individual spray nozzles 5 between adjacent strand guide rollers 4 is associated with an adjusting device 8, with which the spray nozzles 5 can be positioned in their position to the strand surface. Specifically in the strand guide segments 6 a plurality of spray nozzles 5 arranged one behind the other in the strand conveying direction S are connected via a connecting common spray bar 7 to an adjusting device 8 common to these spray nozzles. The adjusting devices 8 and the associated spray nozzles 5 are assigned horizons H1 to H6. In the case of individually adjustable spray nozzles, horizons H1 to H4 lying in a common plane are associated with these and the associated adjusting device 8, when a plurality of spray nozzles 5 located one behind the other in the strand transport direction via a common spray bar 7 and a common adjusting device 8, this combination of spray nozzles is in each case a horizon H5. Assigned to H6.

Figure 2 shows a device configuration for the implementation of the method according to the invention in a continuous casting and illustrates the interaction of the continuous casting mold 1 and the coolant application with a cooling device 10 in the strand guide, as is done for example in the horizon H3 of the strand guide of Figure 1. In particular, in FIG. 2, the cooling conditions are shown in the case of an eccentric positioning of the metal strand 2 with respect to the plant-fixed, dot-dash line symmetry axis 11 of the strand guide. This situation occurs when, for example, to reduce local wear on the wide side walls 1a at intervals

Parallel displacement of the narrow side walls 1b takes place with the Schmalseitenverstelleinrichtungen 1c.

The metal strand 2 formed in the continuous casting mold 1 has a casting width B and is positioned eccentrically in relation to the axis of symmetry 11 by the adjustment of the narrow side walls 1 b made at a certain point in time. With formed as a position encoder position detection or position determining devices 1 d, the narrow-side adjusting 1c associated with their time-dependent instantaneous position and its time history and thus the strand width and the strand position is detected continuously or discontinuously time-dependent and fed the data obtained to a computing unit 12. Some of the metal strand supporting and leading strand guide rollers 4 are equipped with a motor drive 13 and a speed measuring device 14 for detecting the instantaneous transport speed of the metal strand 2 and its time course, for example with a speed sensor. These measurement data are fed to the arithmetic unit continuously. In addition, control data can be fed from the plant control system of the continuous casting plant via a data line 15.

In the arithmetic unit 12, it is calculated on the basis of a mathematical model, when a change in position in the continuous casting mold in the individual horizons of the strand guide takes effect, i. with which time delay or at which time the position of the metal strand assumed in the continuous casting mold 1 also occurs in the respective horizon of the strand guide 3. The calculated time and the predetermined strand position from the continuous casting mold 1 form the manipulated variables for the positioning of the spray nozzles 5 of the cooling device 10 in the individual horizons of the strand guide 3. The control signals control adjusting cylinder 8a, 8b of adjusting 8, the spray nozzles 5 parallel in a direction of movement to the generatrix 16 of the coolant spray cone 17 with the spray angle a move. In a lateral change in position of the metal strand in the horizon position change is dependent on a spray nozzle 5a outwardly and the other spray nozzle 5b moves inward, depending on the instantaneous strand width proportions relative to the axis of symmetry 11. Thus, an individual tracking of the coolant application to the metal strand in each horizon of the strand guide allows ,

The detailed mechanical structure of the spray nozzle adjustment device is already described in WO 2007/121804 A1 and is applied analogously to the subject matter of the present invention with continuously or discontinuously changing strand width or with asymmetrical width adjustment with respect to an axis of symmetry. A common adjusting device for a plurality of spray nozzles arranged in succession in the strand conveying direction with a common spray bar is already described in WO 2007/12804 A1 and is used here in the same constructive embodiment. The adjustment to time-variable asymmetry conditions is realized by the individual control of the arranged on both sides of the axis of symmetry adjustment for the spray nozzles.

FIG. 3 schematically illustrates the independent coolant supply of the spray nozzles 5a, 5b arranged on either side of the axis of symmetry 11 for the specific case of a single cast metal strand 2 which is moved asymmetrically to the axis of symmetry by the strand guide of the continuous casting plant. Central coolant lines 20a, 20b are associated with supply devices with metering devices 21a, 21b, which ensure a controlled distribution of coolant quantity to the individual spray nozzles 5a, 5b via supply lines 22a, 22b. The supply devices with metering devices 21a, 21b can according to a further embodiment also regulate the injection pressure of the coolant as a function of default values of the computing unit. Several spray nozzles can be connected via a common spray bar 23 (shown in phantom) to a common supply line 22a, 22b.

FIG. 4 schematically illustrates, in a representation analogous to FIG. 3, the independent coolant supply of the spray nozzles 5a, 5b arranged on either side of the symmetry axis 11 for the special case of two parallel cast metal strands 2a, 2b of unequal strand width, which are moved asymmetrically to the symmetry axis by the strand guide of the continuous casting plant , This case occurs in twin-continuous casting, which are suitable by a special design of the continuous casting mold to cast two metal strands of different widths or alternatively suitable for casting a strand or two contrast narrower strands. The central coolant lines 20a, 20b are analogous to Figure 3 supply devices associated with metering devices 21a, 21b, which ensure a regulated distribution of coolant quantity to the individual spray nozzles 5a, 5b via supply lines 22a, 22b. The supply devices with metering devices 21a, 21b can according to a further embodiment also regulate the injection pressure of the coolant as a function of default values of the computing unit. Several spray nozzles can be connected via a common spray bar 23 (shown in phantom) to a common supply line 22a, 22b.

LIST OF REFERENCES: 1 continuous casting mold 1a wide side walls 1b narrow side walls 1c narrow side adjustment device 1d position detection or positioning device 2, 2a, 2b metal strand 3 strand guide 4 strand guide rollers 5, 5a, 5b spray nozzles 6 strand guide segment 7 spray bar 8 adjusting the spray nozzles 8a, 8b adjusting cylinder HO output horizon H1 .... .H6 Horizon in the strand guide 3 10 Cooling device 11 Symmetry axis of the strand guide 12 Computing unit 13 Drive of the strand guide roller 14 Speed measuring device 15 Data line 16 Creator of the coolant spray cone 17 Coolant spray cone 20a, 20b Central coolant line 21a, 21b Supply device with metering device 22a, 22b Supply line 23 Spray bar B strand width S strand conveying direction a spraying angle

Claims (14)

1. A method for applying coolant to a cast metal strand (2, 2a, 2b) in a continuous casting, wherein the metal strand in a cooled continuous casting mold (1) with one of narrow side walls (1b) defined strand width (B) is formed and the partially solidified metal strand then passed through a strand guide (3) and in this continuously in several horizons (H1 ..... H6) is cooled, the coolant application in the strand guide is carried out depending on the strand width, characterized in that at a time-varying strand width and / or strand position in the continuous casting mold (1) the respective instantaneous positions of the narrow side walls (1b) are continuously or discontinuously detected and taking into account the casting speed, the coolant application to the metal strand in successive horizons (H1 ..... H6) of the strand guide (3) according to himself carried-changing strand width and / or train position. 2. The method according to claim 1, characterized in that the transport time of the metal strand of an initial horizon (HO) in the continuous casting mold (1) to the respective horizon (H1, ..., H6) of the coolant application in the strand guide (3) is preferably calculated from the casting speed, for the positioning of the spray nozzles (5, 5a, 5b) of a cooling device (10) in the respective horizons of the strand guide (3) is used. 3. The method according to claim 1 or 2, characterized in that the coolant application in a horizon (H1, ..., H6) of the strand guide (3) by at least two spray nozzles (5a, 5b) takes place. 4. The method according to any one of the preceding claims, characterized in that the individual spray nozzles (5a, 5b) allocated coolant quantity is determined in dependence of the spray nozzle spacing of the metal strand surface or the coated on the metal strand surface spray width. 5. The method according to any one of the preceding claims, characterized in that during the transport time from the initial horizon (HO) in the mold (1) to the respective horizon (H1 ..... H6) of the coolant application in the strand guide (3) already Cooling taken into account in the determination of the amount of coolant still applied. 6. The method according to any one of the preceding claims, characterized in that the time-varying strand width and / or strand position in an initial horizon (HO) of the continuous casting mold (1) by position detection or position determining means (1d) is detected, said data by one of Narrow side wall (1b) of the mold (19) associated with position encoders measured or predetermined by an associated control device or a computing unit (12), this data processed in a control device or a computing unit and control signals for the time-dependent positioning of the spray nozzles (5, 5a, 5b) generated in the respective horizons (H1, ..., H6) of the strand guide (3) and adjusting devices (8) of the spray nozzles are supplied transport time dependent. 7. The method according to any one of the preceding claims, characterized in that the coolant application to the metal strand in a horizon (H1 ..... H6) of the strand guide by at least two independently positionable spray nozzles (5a, 5b) or spray nozzles carrying spray bars (23 ), wherein the adjustment direction (8) of the spray nozzles (5a, 5b) is determined by the generatrix (16) of the spray cone of the coolant jet or by the spray angle (a) in the width direction of the coolant jet. 8. Continuous casting plant for the continuous production of a metal strand (2, 2a, 2b) with at least one continuous casting mold (1) for forming a partially solidified metal strand having a predetermined strand width and strand thickness, wherein the continuous casting mold (1) broad side walls (1a) and relative to these positionable narrow side walls ( 1 b), and with a continuous casting mold (1) downstream strand guide (3) for supporting and guiding the metal strand, in the cooling means (10) for applying a coolant to the metal strand in several horizons (H1, ..., H6) are arranged and which adjusting devices (8) for positioning of spray nozzles (5, 5a, 5b) depending on the strand width (B) are assigned, characterized in that the narrow side walls (1b) position detection or position determining means (1d) for determining the current Strand width and / or the current strand position are assigned in the mold, a Control device or a computer unit (12) for receiving and processing currently-dependent instantaneous values of the strand width and / or strand position and for generating actuating signals for positioning the spray nozzles (5, 5a, 5b) of the cooling devices (10) in the individual horizons (H1, .. ., H6) of the strand guide (3) is provided and independently controllable adjusting devices (8) for spray nozzles (5, 5a, 5b) or spray nozzle groups are provided in the individual horizons of the strand guide. 9. continuous casting plant according to claim 8, characterized in that the position detection or position determining means (1d) of one of the narrow side wall (1b) of the continuous casting mold (1) associated with the position sensor is formed. 10. Continuous casting plant according to claim 8 or 9, characterized in that in the strand guide (3) is provided a speed measuring device (14) for detecting current-dependent casting speed. 11. Continuous casting plant according to one of the preceding claims 8 to 10, characterized in that the independently controllable adjusting devices (8) of the spray nozzles (5, 5a, 5b) comprise adjusting cylinder (8a), which allow a linear adjustment of a spray nozzle, wherein the Direction of movement of the respective spray nozzle (5, 5a, 5b) or a spray nozzle carrying spray bar (7) parallel to the generatrix of the coolant spray cone (17) of the coolant jet or by the spray angle (a) in the width direction of the coolant jet in the associated horizon (H1 ... ..H6) corresponds. • · · · · ···· 12. Continuous casting plant according to one of the preceding claims 8 to 11, characterized in that the spray nozzles (5, 5a, 5b) coolant supply devices with metering devices (21a, 21b) are assigned to the controlled Kühlmittelmengenzuteilung. 13. Continuous casting plant according to one of the preceding claims 8 to 12, characterized in that several in the strand conveying direction successively arranged spray nozzles (5a or 5b) is assigned a common adjusting device (8) in a horizon (H1, ..., H6). 14. Continuous casting plant according to one of the preceding claims 8 to 12, characterized in that the strand guide (3) of several strand guide segments (6) is formed and in each segment in the strand conveying direction successively arranged spray nozzles (5a or 5b) at least one common adjusting device (8 ) is assigned in a horizon (H1, ..., H6).