WO2017042059A1

WO2017042059A1 - Secondary cooling of a strand in a strand casting system

Info

Publication number: WO2017042059A1
Application number: PCT/EP2016/070441
Authority: WO
Inventors: Christian ENZINGER; Thomas Fuernhammer; Thomas Stepanek; Helmut Wahl
Original assignee: Primetals Technologies Austria GmbH
Priority date: 2015-09-07
Filing date: 2016-08-31
Publication date: 2017-03-16

Abstract

The invention relates to a cooling device (7) and to a cooling method for the secondary cooling of a strand (9) in a strand guide (5) of a strand casting system (1). The cooling device (7) comprises a coolant distribution system (15) with line segments (17. to 17.4) for conducting a coolant (19), multiple coolant outlets (21) distributed over the strand guide (5) for dispensing a respective individual coolant flow (Q) onto the strand (9), at least one switching valve (23) with which at least one individual coolant flow (Q) can be activated and deactivated, and a control unit (27) which is designed to modulate the pulse width of at least one individual coolant flow (Q) in at least one flow region (ΔQ) for a time average value (Ǭ) of the individual coolant flow (Q) by actuating a switching valve (23) in a pulse width-modulated manner.

Description

description

Secondary cooling of a strand in a continuous casting plant The invention relates to a cooling device and a

Cooling method for secondary cooling of a strand in a strand guide of a continuous casting plant.

In continuous casting in a continuous casting plant, a metallic strand is formed in a mold and then guided in a strand guide and thereby further cooled. The cooling of the strand in the strand guide is called

Secondary cooling refers to cooling of the strand in the mold called primary cooling. In the

Secondary cooling is applied by means of a cooling device on the strand usually a coolant, such as water or a water-air mixture.

From EP 2 527 061 AI a secondary cooling device and a cooling method for secondary cooling of a strand in a continuous casting plant is known, in which the cooling power is adjusted by a PWM control of the duty cycle of a switching valve. How the ratio between the maximum and the minimum individual coolant flow increases and in addition the formation of a suitable beam profile (in particular the opening angle of the coolant jet from the coolant outlet) can be achieved even with small individual coolant flows does not appear from the document. The invention has for its object to provide an improved cooling device and an improved cooling method for secondary cooling of a strand in a continuous casting. In particular, the ratio between the maximum amount of coolant that can be applied and the minimum amount of coolant that can be applied should be increased.

The object is achieved according to the invention

Cooling device by the features of claim 1 and with regard to the cooling method by the features of claim 10.

Advantageous embodiments of the invention are the subject of the dependent claims.

A cooling device according to the invention for the secondary cooling of a strand in a strand guide of a continuous casting plant comprises a coolant distribution system with line segments for conducting a coolant and several of them

Strand guide distributed coolant outlets for the output of a single coolant flow on the strand,

at least one switching valve, with the at least one

Coolant single stream on and can be switched off, a

Control unit, which is for a pulse width modulation of at least one Kühlmitteleinzelstroms in a current range for a time average value of the Kühlmitteleinzelstroms by a pulse width modulated control of a switching valve

is formed and a control loop for controlling a coolant pressure or coolant flow in the

Coolant distribution system.

The cooling device thus enables a strand produced in a continuous casting plant

Cooling pulse width modulated coolant single streams that are output from distributed via a strand guide coolant outlets. In this case, the pulse width modulation is realized in a current range for a time average of a single coolant flow. In the

Pulse width modulation of a single coolant flow

the coolant singletream disappears during part of each pulse width modulation clock period and assumes a constant, non-zero current pulse value during the other part of each clock period. This current pulse value is therefore greater than the time average of the

pulse width modulated single coolant flow. This is particularly advantageous if the time average to be set is so small that an unpulsed, ie temporally constant, single coolant flow which would produce this mean value has a planned beam profile of one generated by the coolant single stream

Coolant jet can not realize due to a low refrigerant pressure. In fact, the beam profile, in particular an opening angle of the coolant jet, is essential for the size of the coolant wetted by the coolant jet

Range of the strand and thus for the cooling effect of the coolant jet. To produce a designated

Beam profiles, the coolant outlets are preferably formed by respective outlet nozzles. The size of the

Coolant single stream corresponds to one

Coolant pressure, which is not sufficient to produce the intended beam profile at too small coolant single stream.

Therefore, a pulse width modulation of a

Coolant single stream preferably carried out in a current range which is limited by a threshold current at which the coolant pressure would not be sufficient to realize a provided jet profile of a coolant jet generated by the coolant single stream at a fully open switching valve. By the

Pulse width modulation of the coolant single stream can be realized with current pulse values that are greater than the threshold current, average values of the coolant single stream that are smaller than the threshold current. In other words, it is possible to realize individual coolant streams whose time averages are smaller than the threshold current and which nevertheless have an intended beam profile of the

Coolant jet generate, since the current values are greater than the threshold current.

Due to the pulse width modulation in particular of

Coolant individual streams whose time averages are smaller than the threshold current can therefore have coolant jets of an intended beam profile Ls over a larger one Stromwerteintervall be realized as in an exclusive use of unpumped Kühlmitteleinzelströme, ie the cooling device can in a larger

Operating window defined by this current value interval.

Above the threshold current can be unpulsed

Coolant single streams are generated by controlling a coolant pressure or coolant flow in the coolant distribution system with the control loop:

The invention also makes it possible to expand the operating window of existing conventional cooling devices in a relatively simple and cost-effective manner, ie. H. to transform these cooling devices such that

Can be realized coolant jets of a designated beam profile over a larger Stromwerteintervall the Kühlmitteleinzelströme. All you need is for that

Switching valves and connected to the switching valves control unit for the pulse width modulated switching on and off of coolant single streams are installed, for example by existing conventional line segments through

Line segments replaced with switching valves and the

Switching valves are connected to the control unit via (compared to refrigerant lines cost-effective) control lines, without costly to change or replace the coolant distribution system as a whole. Such a transformation can also advantageously be carried out gradually, so that the operation of the continuous casting must be interrupted only for relatively short conversion times.

As switching valves are, for example pneumatically or electrically or electromagnetically or hydraulically switchable valves. Such trained switching valves are advantageously commercially available and allow a cost-effective implementation of switched on and off coolant single streams. As already mentioned above, the coolant outlets are preferably each formed by an outlet nozzle. A further embodiment of this embodiment of the invention provides that at least one outlet nozzle has an exchangeable nozzle tip.

By means of outlet nozzles formed coolant outlets can be particularly suitable for strand cooling particularly suitable

Beam profiles of the output from the coolant outlets coolant jets are generated. Outlet nozzles with

Replaceable nozzle tips allow advantageous to modify these beam profiles, if necessary, in a simple manner by replacing the nozzle tips.

Further embodiments of the invention provide that either with each switching valve exactly one

Single coolant flow or with at least one switching valve a plurality of individual coolant streams can be switched on and off.

Switching valves, each with exactly one

Coolant single stream on and can be switched off, are

can be switched faster than identical switching valves for a plurality of individual coolant streams, thereby enabling a higher clock frequency of the pulse width modulation of the individual coolant streams. Furthermore, by individually controlling the switching valves, they enable more flexible control of the cooling and reduce the effects of a failure of a single switching valve. On the other hand, switching valves for a plurality of coolant individual streams advantageously reduce the number of switching valves required and thus the costs and the outlay for realizing the

Cooling device with respect to switching valves for each a single coolant flow. It therefore depends on the

respective requirements for the cooling device from whether switching valves for each a single coolant flow or multiple Kühlmitteleinzelströme are more advantageous. Further embodiments of the invention provide at least one longitudinal row of a plurality of coolant outlets arranged one behind the other along a transport direction of the strand and / or at least one transverse row of a plurality of coolant outlets arranged side by side transversely to a transport direction of the strand.

These embodiments advantageously enable a uniform distribution over a portion of a strand guide

Secondary cooling of a strand, especially if the

Cooling device each having a plurality of longitudinal and transverse rows of coolant outlets.

A further embodiment of the invention provides a

Pressure sensing device for detecting a

Coolant pressure or a flow meter for detecting a flow of coolant in the coolant distribution system before.

Such a pressure sensing device allows

Advantageously, an analysis and review of functions of the cooling device, for example, the determination of a degree of clogging of coolant outlets, by a

Evaluation of the detected by the pressure sensing device signals. In addition, an actual value of a coolant pressure or coolant flow for controlling the coolant pressure or coolant flow in the coolant distribution system can be detected.

In a cooling method according to the invention for

Secondary cooling of a strand in a strand guide of a continuous casting plant by an inventive

Cooling device are a threshold current Q _s for

temporal means Q of at least one

Coolant single and a lying below the threshold current or equal to the threshold current current range AQ specified. For the current range AQ, Q = [0, Q _s ]. In the current range lying temporal means of Single refrigerant flows with 0 -SQ -SQ _s are generated by adjusting a refrigerant pressure in the refrigerant distribution system to a constant pressure value and each

Single coolant flow through a pulse width modulated

Control of a switching valve with a dependent of the average value to be generated duty cycle

is pulse width modulated. Out-of-range time averages of individual refrigerant flows with Q> Qs are generated by opening the switching valves of these individual refrigerant flows and the

Coolant pressure or a coolant flow in the

Coolant distribution system with the control loop dependent on one of the individual coolant streams to be generated

Setpoint is controlled.

With the cooling method, the above-mentioned advantageous enlargement of the operating window of the

Cooling device realized against a use of unpumped Kühlmitteleinzelströme.

An embodiment of the cooling method provides that a plurality of individual coolant streams are pulse-width modulated in the current range for their time average values in such a way that a total coolant flow formed together by all these individual coolant streams is constant over time.

This embodiment of the invention thus provides a

time-delayed switching on and off of

Kühlmitteleinzelströmen before in their pulse width modulation in order to keep constant a constant of all of these individual refrigerant flows formed coolant flow. This can advantageously be a uniform of the

Cooling device delivered to the strand

Coolant total flow can be generated, even if the output from the individual Kühlmittelauslässen

Coolant individual streams each pulse width modulated. A further refinement of the cooling method provides that a plurality of individual coolant streams are pulse-width modulated in the current range for their time average values in such a way that a total coolant flow formed by all these individual coolant streams is regulated to a desired value. An actual value of the

Coolant total current determined and a duty cycle and a period length of a clock period of the pulse width modulation are controlled in response to a deviation of the determined actual value of the desired value.

This embodiment of the invention advantageously makes it possible to control a total coolant flow output from a plurality of coolant outlets to a predefinable desired value by setting the duty cycle and the period length of the

Pulse width modulation of the individual coolant flows. In order to determine the actual value of the total coolant flow, for example, in each case coolant pressures are detected in line segments, are output via the Kühlmitteleinzelströme, and closed by means of current-pressure characteristics on each output Kühlmitteleinzelströme. The actual value of the total coolant flow is then the sum of these

Coolant single currents, each multiplied by the respective duty cycle of the pulse width modulation formed.

A further embodiment of the cooling method provides that a selection of coolant outlets, through which

Coolant individual streams are issued, is made in response to a width of the strand.

As a result, the cooling of a strand can advantageously be adapted to its width. By Kühlmittelauslässe that are not needed to cool a strand, as they are located next to the strand surface, are doing

For example, only each discharge air in a pulse pause or a short water pulse delivered to prevent clogging of these coolant outlets. Another embodiment of the invention provides that a coolant pressure in the coolant distribution system is detected and evaluated to determine a degree of clogging of at least one coolant outlet.

This can advantageously a malfunction of

Cooling device by a blockage of

Kühlmittelauslässen, which has a lack of cooling of the strand result, can be detected.

In order to apply the same area of the strand through a coolant outlet at different casting speeds, it is advantageous if the clock frequency f = 1 / T

is set in proportion to the casting speed of the continuous casting plant. For example, a strand moving at a casting speed of 0.05 m / s moves

Secondary cooling passes, and is cooled by a coolant outlet at a frequency of 0.5 Hz and a duty cycle D of 50%, during a single cooling cycle by 0.05 m on. If the casting speed is now doubled to 0.1 m / s and the duty cycle D is kept constant at 50%, then the cycle frequency must also be doubled to 1 Hz so that the strand continues to move by 0.05 m during a single cooling cycle.

In addition, it has proved to be advantageous if the duty cycle D is kept constant at different casting speeds, but the coolant single stream (Q) through a coolant outlet (21) proportional to

Casting speed is set. This means that when doubling the casting speed at the same clock frequency and the same duty cycle of the coolant flow must be doubled to spend the same amount of coolant in the same cooling cycle.

If, however, not a single coolant flow but the coolant pressure is set, then it is favorable, in turn, the duty cycle D at different casting speeds held constant and the coolant pressure (P) is set in proportion to the square of the casting speed. This leads to a doubling of the

Casting speed at the same clock frequency and the same duty cycle of the refrigerant pressure must be quadrupled in order to spend the same amount of coolant in the same cooling cycle.

In order to achieve a uniform jet profile, ideally a constant opening angle, of a coolant jet even with different coolant pressures or flows, it is advantageous if the coolant pressure or the

Coolant flow is set in the coolant distribution system such that sets in the coolant outlet turbulent flow with Re> 2300.

The Reynolds number Re (for example, the wikipedia.org/gui/reynolds number)

v. d

Re =,

v

where v is the flow velocity of the coolant in the coolant outlet, d is the characteristic length of the coolant

Coolant outlet and v indicates the kinematic viscosity of the coolant is a dimensionless measure of the flow conditions in the coolant outlet. It is thus the case that identical beam profiles result for identical Reynolds numbers.

The threshold Q _s is preferably selected such that adjusts a turbulent flow for each individual coolant flow through the respective coolant outlet.

A continuous casting plant according to the invention comprises a mold for forming a strand, an oscillating device for

Moving the mold relative to the strand, a strand guide for supporting and guiding the strand and a cooling device according to the invention for the secondary cooling of the strand with the advantages already mentioned above. In this case, the mold has a width adjustment for adjusting a width of the strand and the strand guide preferably has a Gießdickenverstellung for adjusting a thickness of the strand on. As a result, strands of different widths and thicknesses can advantageously be produced. By Osszilationseinrichtung advantageous movements of the mold, in particular oscillating movements of the mold, can be generated so that the strand does not adhere to an inner surface of the mold.

The above-described characteristics, features and advantages of this invention as well as the manner in which they are achieved will become clearer and more clearly understood

Related to the following description of

Embodiments associated with the

Drawings are explained in more detail. Showing:

1 shows schematically a detail of a continuous casting plant in a side view,

2 shows schematically a first embodiment of a

Cooling device for secondary cooling of a strand in a continuous casting plant in a perspective view,

3 shows a perspective view of a

End of line segment of a cooling device for

Secondary cooling of a strand in a continuous casting plant,

4 shows schematically a second embodiment of a

5 shows a diagram of a coolant pressure as a function of a single coolant flow of an outlet nozzle,

6 shows a diagram of a time profile of a pulse width modulated Kühlmitteleinzelstroms a

outlet nozzle, 7 shows diagrammatically time profiles of pulse-width-modulated coolant flows, which of a

Cooling device for secondary cooling of a strand are issued in a continuous casting,

8 shows a duty cycle D of a pulse width modulation of a

Kühlmitteleinzelstroms depending on the average value of the Kühlmitteleinzelstroms, and 9 shows a control circuit for controlling a

Coolant pressure or coolant flow in one

Coolant distribution system.

Corresponding parts are provided in all figures with the same reference numerals.

FIG. 1 schematically shows a section of a

Continuous casting 1 in a side view. Shown are a mold 3, an oscillating device 4 for moving the mold 3 relative to a strand 9, a downstream of the mold 3 strand guide 5 and a cooling device 7 of the continuous casting 1. In order not to unnecessarily increase the complexity of the figure, the strand guide rollers 13 above the Strand 9 and the line segments 17.1 and the coolant outlets 21 below the strand 9 not shown. The person skilled in the art is aware that a strand after emerging from a mold in the secondary cooling is typically guided by strand guide rollers above and below the strand and the upper and lower broad sides of the strand are cooled.

The mold 3 is supplied with a metallic melt, from which the mold 3 is formed with the metallic strand 9, which is guided with the strand guide 5 and along a

Transport direction 11 is transported. With the

Osszilationseinrichtung 4 movements of the mold 4, in particular oscillating movements (the direction of movement is shown by an arrow) of the mold 4, produced, so that the strand 9 does not adhere to an inner surface of the mold. The strand guide 5 has several

Strand guide rollers 13 to support the strand 9.

The mold 3 has a width adjustment for adjusting a width of the strand 9, so that with the

Mold 3 strands 9 different widths are generated. The strand guide 5 has a Gießdickenverstellung for adjusting a thickness of the strand 9, so that with the strand guide 5 strands 9 of different thicknesses can be generated.

The cooling device 7 serves for the secondary cooling of the strand 9 in the strand guide 5. The cooling device 7 comprises a coolant distribution system 15

Line segments 17.1 to 17.4 for managing a

Coolant 19 and more over the strand guide. 5

distributed coolant outlets 21 for the issue of

Coolant 19 on the strand 9. With reference to the figures 2 to 4 below various embodiments of

Cooling devices 7 described in more detail. The coolant 19 is, for example, water.

The continuous casting plant 1 shown in FIG. 1 is designed for so-called horizontal continuous casting, in which the strand 9 is output horizontally from the mold 3 to the strand guide 5. The invention, in particular a

cooling device 7 according to the invention, but is not limited to continuous casting 1 for horizontal continuous casting, but also relates in particular continuous casting 1, which are designed for so-called vertical continuous casting, in which the strand 9 vertically through a bottom opening of the mold 3 from the mold 3 to the strand guide 5 is issued and the strand guide 5 is executed bent, so that the strand 9 along the strand guide 5 of a

horizontal is brought into a vertical position. Figure 2 shows schematically a first embodiment of a cooling device 7 for secondary cooling of a

Strand 9 in a continuous casting plant 1 in one

perspective view. In this case, only a portion of the strand 9 is shown, which is in the range of

Cooling device 7 is located. Further, from this

Section of the strand 9 and of the

Coolant distribution system 15 of the cooling device 7 only one area shown, which is over half the width of the strand 9 from a lateral

Strand edge 9.1 of the strand 9 up to a parallel to

Transport direction 11 extending central axis 9.2 of

Strand 9 extends. Over the other half of the width of the strand 9, a further region of the

Coolant distribution system 15, which is formed as well as the area shown in Figure 2, these two areas are mirror-symmetric with respect to a mirroring on a mirror plane containing the central axis 9.2 and perpendicular to a strand surface 9.3 of the strand 9.

The coolant outlets 21 of the coolant distribution system 15 form a plurality of longitudinal rows along the transport direction 11 of the strand 9 arranged one behind the other

Coolant outlets 21. The longitudinal rows are arranged transversely to the transport direction 11 of the strand 9 side by side, so that coolant outlets 21 of different longitudinal rows form transverse rows transversely to the transport direction 11 adjacent coolant outlets 21.

In the embodiment shown in Figure 2, the coolant distribution system 15 eight juxtaposed longitudinal rows of coolant outlets 21, wherein each

Longitudinal row four coolant outlets 21 has. Alternative embodiments have one of eight different number of juxtaposed longitudinal rows of

Kühlmittelauslässen 21 and / or at least one longitudinal row with one of four different number of

Coolant outlets 21 on. Each coolant outlet 21 forms a strand 9

facing end of a line end segment 17.1, the

perpendicular to the strand surface 9.3 runs. For each longitudinal row of coolant outlets 21 has the

Coolant distribution system 15 a parallel to

Transport direction 11 extending longitudinal segment segment 17.2, which has these these coolant outlets 21

Line end segments 17.1 connects to each other. The

Coolant distribution system 15 also has a transverse to

Transport direction 11 extending transverse line segment 17.4, with each longitudinal segment segment 17.2 via a respective perpendicular to the strand surface 9.3 extending

Line intermediate segment 17.3 is connected. each

Line end segment 17.1 also has to issue

Coolant 19 an outlet nozzle 33 with the

Coolant outlet 21, see Figure 3.

In each line end segment 17.1, a switching valve 23 is arranged, with which a coolant supply of coolant 19 to the coolant outlet 21 of this line end segment 17.1 can be interrupted. Each switching valve 23 is designed as an open / close valve, which has two operating states, wherein the switching valve 23 in a first

Operating condition, the coolant supply to the

Coolant outlet 21 releases and in the second

Operating condition, the coolant supply to the

Coolant outlet 21 locks. A change of the

Operating state of a switching valve 23 is here as

Switching the switching valve 23 denotes; switching from the first to the second operating state is referred to as closing the switching valve 23, and switching from the second to the first operating state is referred to as opening the switching valve 23. By each switching valve 23 so exactly one Kühlmitteleinzelstrom Q is switched on and off, which is output from a coolant outlet 21. The switching valves 23 are connected via control lines 25.1 to 25.4 with a control unit 27 and through the

Control unit 27 switchable. Each connects

Control line 25.1 to 25.4, the switching valves 23 a

Longitudinal row of coolant outlets 21 with the

Control unit 27. The control lines 25.1 to 25.4 can at least partially in pipes of

Line segments 17.1 to 17.4 run, see. the

Description of Figure 3 below.

The switching valves 23 are designed as pneumatically or electrically or electromagnetically or hydraulically switchable valves. Accordingly, the control lines 25.1 to 25.4 in the case of pneumatically switchable switching valves 23 pneumatic air pressure lines, in the case of electrically or electromagnetically switchable switching valves 23 electrical lines and in the case of hydraulically switchable

Switching valves 23 hydraulic fluid lines. The control unit 27 is adapted to the

To switch switching valves 23 in a manner described below.

The cooling device 7 further comprises a

Pressure sensing device 29 for detecting the

Coolant pressure P in the coolant distribution system 15. The detected by the pressure detecting device 29 signals are supplied via a pressure signal line 31 of the control unit 27. The control unit 27 evaluates these signals for analysis and verification of functions of

Cooling device 7, for example, to determine a degree of clogging of the coolant outlets 21, from.

FIG. 3 shows a perspective view of a

End of line segments 17.1. The line end segment 17.1 comprises a segment tube 35, a connecting flange 37, a

Switching valve 23 and an outlet nozzle 33rd The connecting flange 37 is at a first end of the

Segment tube 35 and arranged with a

Longitudinal segment 17.2 connectable. At the second end of the segment tube 35, the switching valve 23 is arranged on this end of the segment tube 35, for example by a

Pipe-valve screw 39, which by an external thread on the outer surface of the segment tube 35 and a

corresponding internal thread of the switching valve 23 is formed, can be screwed.

The outlet nozzle 33 has a nozzle tip 33.1 with a coolant outlet 21 and a nozzle main body 33.2. The nozzle main body 33.2 is arranged on the switching valve 23 and the switching valve 23, for example by a valve-nozzle screw 41, which by an external thread on the outer surface of the switching valve 23 and a

corresponding internal thread of the nozzle body 33.2 is formed, screwed. The nozzle tip 33.1 is arranged on the nozzle main body 33.2. For example, the nozzle body 33.2 has an internal thread, which leads to a

External thread of the nozzle tip 33.1 corresponds, so that the nozzle tip 33.1 is detachably connectable to the nozzle body 33.2. As a result, a jet profile of a coolant jet output by the outlet nozzle 33 can advantageously be changed by changing the nozzle tip 33.

The segment tube 35 serves to guide coolant 19 to the coolant outlet 21 and guide an end portion of a control line 25.1 to 25.4 to the switching valve 23. For this purpose, the segment tube 35, for example, an outer tube and an inner tube extending in the outer tube, wherein between the outer tube and the inner tube coolant 19 is guided and the inner tube, the end portion of a

Control line 25.1 to 25.4 forms or surrounds. Of the

Connecting flange 37 has two flange openings 37.1, 37.2, wherein a first flange opening 37.1 of the supply of coolant 19 in the segment tube 35 and the second flange 37.2 serves the guide of the control line 25.1 to 25.4 is used in the segment tube 35. The connecting flange 37 furthermore has a centering bolt 42, which is arranged between the flange openings 37.1, 37.2, in order to move the

Line end segment 17.1 easier to assemble and align.

Figure 4 shows schematically a second embodiment of a cooling device 7 for secondary cooling of a

Strand 9 in a continuous casting plant 1 in an analogous to Figure 2 perspective view. The embodiment shown in Figure 4 differs from the embodiment shown in Figures 2 and 3, characterized in that not in the line end segments 17.1 each have a switching valve 23 is arranged for a coolant outlet 21, but that for each longitudinal row of

Kühlmittelauslässen 21 only one each over a

Control line 25.1 to 25.4 with the control unit 27th

connected switching valve 23 in one

Intermediate segment 17.3 is arranged so that through each of these switching valves 23, a coolant supply from the line transverse segment 17.4 to a longitudinal segment segment 17.2 and all associated Leitungsendsegmenten 17.1 is interruptible. Further, in contrast to the embodiment shown in Figures 2 and 3, a check valve 43 is disposed in each line end segment 17.1 to after locking a coolant supply to the

Line end segment 17.1 through the corresponding

Switching valve 23, an output of coolant 19, which is in line segments 17.1 to 17.3 between the switching valve 23 and check valve 43 to prevent the strand 9.

Apart from these differences is the

Cooling device 7 of the illustrated in Figure 4

Embodiment similar to the embodiment shown in Figures 2 and 3 formed. In particular, the switching valves 23, like the switching valves 23 of the embodiment shown in FIGS. / To-valves formed, which are switchable by the control unit 27 in the manner described in more detail below. The

Line end segments 17.1 each have a turn

Outlet nozzle 33, the nozzle tip 33.1 is preferably designed to be interchangeable.

Compared with that shown in Figures 2 and 3

Embodiment requires the embodiment shown in Figure 4 advantageously less switching valves 23. Compared to the embodiment shown in Figure 4 allows the illustrated in Figures 2 and 3

Embodiment, however, a higher clock frequency of the pulse width modulated circuit of the switching valves 23 (when using similar switching valves 23 in both

Embodiments), allows for individual control of the switching valves 23 a more flexible control of the cooling and reduces the effects of a failure of a single switching valve 23, since such a failure on a smaller surface area of the strand. 9

effect.

FIGS. 5 to 7 illustrate a cooling method for secondary cooling of a strand 9 in a continuous casting plant 1 with a cooling device 7, which is like one of the exemplary embodiments illustrated in FIGS. 2 to 4

is trained.

FIG. 5 shows a diagram for a coolant pressure P as a function of a single coolant flow Q through an outlet nozzle 33 of the cooling device 7, which is designed like one of the exemplary embodiments illustrated in FIGS. 2 and 4. In the cooling method, the single refrigerant flow Q discharged from the outlet nozzle 33 through the refrigerant outlet 21 is communicated in at least one current range AQ for its time average Q by one

Pulse width modulated control of a switching valve 23 on and off and thus even pulse width modulated, see Figure 6. In the example shown in Figure 5 this is Current range Δζ) is limited by a threshold current Q _s , which corresponds to a threshold pressure P _s . Also shown are a maximum pressure P _M and a corresponding one

Maximum current Q _M , for which the outlet nozzle 33 is designed.

The threshold current Q _s is set such that the coolant pressure P below the corresponding

Threshold pressure P _{s is} no longer sufficient to provide an intended beam profile of one of the outlet nozzle 33

Coolant jet, in particular a designated

Opening angle of the coolant jet, in order to cover a sufficiently large area of the strand surface 9.3 with the coolant jet. Above the threshold current Q _s are the

Kühlmitteleinzelströme Q in the usual way, d. H. output without pulse width modulation. These are the

Switching valves 23 of the individual coolant flows Q to be generated open and the coolant pressure P or a coolant flow in the coolant distribution system 15 is regulated by means of a control circuit 45 to one of the

Coolant individual streams regulated Q dependent setpoint, see Figure 9. Figure 6 shows a course of a pulse width modulated

Coolant single flow Q of an outlet nozzle 33 as a function of a time t. The pulse width modulation has one

Clock period of the period T or a clock frequency L / T. In the illustrated example, the single refrigerant flow Q has a constant non-zero current pulse value Q _P in a first half of each clock period and disappears in the second half of each clock period. Accordingly, the time average Q of the refrigerant single-stream Q in this example is half the current pulse value Q _P.

As a result of the pulse width modulation, with a current pulse value Q _P that is greater than the threshold current Q _s , average values Q of a coolant single-current Q that is smaller can be realized as the threshold current Q _s . In other words, it is possible to realize coolant individual streams Q whose time averages Q are smaller than the threshold current Q _s and which nevertheless have a planned jet profile of one of the

Outlet nozzle 33 produce issued coolant jet.

FIG. 7 shows diagrammatic time profiles of

Coolant streams Gh to Q and a total coolant flow Q _G , of a cooling device 7 for the secondary cooling of a strand 9 in a continuous casting 1 due to a pulse width modulated circuit of the switching valves 23rd

be issued. In this case, the cooling device 7 is like one of those shown in Figures 2 or 4

Embodiments formed, with Figure 7 for simplifying the illustration on a cooling device 7 with only four longitudinal rows of coolant outlets 21 instead of as in the embodiments of Figures 2 and 4 eight

Longitudinal rows refers (Figure 7 may also represent time courses of refrigerant flows Gh to Q and a total coolant flow Q _{G of} the halves shown in Figures 2 or 4 of the respective cooling devices 7, wherein the respective other halves not shown are controlled analogously).

The coolant flows Gh to Q are each of all

Coolant outlets 21 a longitudinal row issued together and are therefore each a sum of

Kühlmitteleinzelströme Q of the coolant outlets 21 a longitudinal row, wherein the Kühlmitteleinzelströme Q are each pulse width modulated analogous to Figure 6. Of the

Total coolant flow Q _G is output from the coolant outlets 21 of all of these longitudinal rows together and is the sum of the coolant flows Qi to Q ₄ .

The switching valves 23 are from the control unit 27th

pulse width modulated with a clock period of the period T or switched at a clock frequency 1 / T. The switching valves 23 for the various longitudinal rows of Coolant outlets 21 connected in time offset to each other, so that the total coolant flow Q _{G is} constant in time. In the example shown in FIG. 7, the

Switching valves 23 connected such that a first

Coolant flow Gh during a second half of each

A second coolant flow Q ₂ disappears during a first and last quarter of each clock period, a third coolant flow Q ₃ disappears during the first half of each clock period, a fourth coolant flow Q ₄ disappears during a second and third quarter of each clock period, and the coolant flows Gh bis Q ₄ in the remaining times assume a constant, non-zero value, which is equal to all longitudinal rows, which is half the total coolant flow Q _G.

The total coolant flow Q _G is thereby at the

Pulse width modulation to a predetermined setpoint

regulated. For this purpose, an actual value of the total coolant flow Q _{G is} determined, and a duty cycle D and the period length T of the pulse width modulation are determined as a function of a

Deviation of the determined actual value from the setpoint regulated. As usual, the duty cycle D of the pulse width modulation is understood to be the ratio of a pulse duration during a clock period to the period length T. In the examples shown in Figures 6 and 7 is the

Duty cycle D, for example, each 50%. In order to determine the actual value of the total coolant flow Q _G , for example, respective coolant pressures P in line segments 17.1 to 17.4 are output via the individual coolant streams Q and are closed therefrom by means of current-pressure curves to the individual coolant flows Q output. The actual value of the total coolant flow Q _G is then formed as the sum of these individual coolant flows Q, in each case multiplied by the respective duty cycle D of the pulse width modulation.

FIG. 8 shows the duty cycle D of the pulse width modulation of a coolant single-flow Q as a function of the average value Q of the coolant single-flow Q in the current range AQ. By doing Current range AQ lying temporal means Q of

Coolant individual streams Q are generated by the

Coolant pressure P is set in the coolant distribution system 15 to a constant pressure value which is at least as large as the threshold pressure P _s , and each

Kühlmitteleinzelstrom Q by a pulse width modulated actuation of a switching valve 23 with a dependent of the generated mean value Q duty D

is pulse width modulated. The duty cycle D therefore increases within the current range AQ with increasing average value Q up to a duty cycle end value D _m . In the case where the refrigerant pressure P in the refrigerant distribution system 15 is set to the threshold pressure P _s , the

Tastgradendwert D _m, for example, the value of 1. When the refrigerant pressure P in the refrigerant distribution system 15 is set to a larger pressure value, the

Duty factor D _m correspondingly smaller.

Further, in the cooling method, a selection of coolant outlets 21 through which refrigerant single streams Q are output is made depending on a width of the string 9. It will be through

Coolant outlets 21, which are not needed to cool the strand 9, since they are located next to the strand surface 9.3, for example, only each exhaust air delivered in a pulse pause or a short water pulse to prevent clogging of these coolant outlets 21.

FIG. 9 shows a control circuit 45 for regulating a

Coolant pressure P or coolant flow in the

Coolant distribution system 15 to produce Kühlmitteleinzelströme Q, which are greater than the threshold current Q _s . The controlled variable R of the control loop 45 is therefore the

Coolant pressure P or coolant flow in the

Coolant distribution system 15. A reference variable S of the control circuit 45 is accordingly one of the

Individual coolant flows Q dependent setpoint of the

Coolant pressure P or coolant flow in the Coolant distribution system 15. The control circuit 45 comprises a regulator 47, a control path 49 and a measuring member 51. The regulator 47 is a pump for directly generating a refrigerant pressure P or coolant flow in the

Coolant distribution system 15, or a pump with a downstream pressure or flow regulator for reducing a generated by the pump coolant pressure P or

Coolant flow in the coolant distribution system 15. The controlled system 49 is the coolant distribution system 15. The measuring member 51 is a pressure detecting device 29 for detecting the refrigerant pressure P or a

Current detection device for detecting a

Coolant flow in the coolant distribution system 15. To control the controlled variable R, a control deviation E of the controlled variable R is formed by the reference variable S. The controller 47 generates a dependent on the deviation E

Command value U to reduce the deviation B.

Although the invention has been further illustrated and described in detail by way of preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

I continuous casting plant

3 mold

4 oscillation device

5 strand guide

7 cooling device

9 strand

9.1 strand edge

9.2 central axis

9.3 strand surface

II transport direction

13 strand guide roller

15 Coolant distribution system 17.1 Line end segment

17.2 Line longitudinal segment

17.3 Intermediate line segment

17.4 Cable cross segment

19 coolant

21 Coolant outlet

23 switching valve

25.1 to 25.4 control line

27 control unit

29 Pressure sensing device 31 Pressure signal line

33 outlet nozzle

33.1 Nozzle tip

33.2 nozzle body

35 segment tube

37 connecting flange

37.1, 37.2 Flange opening

39 pipe valve screw connection

41 valve-nozzle screw connection

42 centering bolts 43 non-return valve

45 control loop

47 controller

49 controlled system

51 measuring element

D duty cycle

D _m duty cycle end value

E control deviation

P coolant pressure P _s threshold pressure

P _M maximum pressure

R controlled variable

Q Coolant single stream

Q _P current pulse value

Qi to Q ₄ coolant flow

Q _G total coolant flow

Q _s threshold current

Q _M maximum flow

AQ power range

Q mean value

S reference variable t time

T period length

U manipulated variable

Claims

claims

1. cooling device (7) for secondary cooling of a

Strand (9) in a strand guide (5) one

Continuous casting plant (1) comprising the cooling device (7)

- A coolant distribution system (15) with

Line segments (17.1 to 17.4) for the management of a

Coolant (19) and a plurality of distributed over the strand guide (5) coolant outlets (21) for outputting a respective Kühlmitteleinzelstroms (Q) on the strand (9),

- At least one switching valve (23), with the at least one Kühlmitteleinzelstrom (Q) is switched on and off,

- A control unit (27), which for a pulse width modulation of at least one Kühlmitteleinzelstroms (Q) in one

Current range (AQ) for a time average (Q) of the Kühlmitteleinzelstroms (Q) by a pulse width modulated control of a switching valve (23) is formed

- And a control circuit (45) for controlling a

Coolant pressure (P) or coolant flow in the

Coolant distribution system (15).

2. Cooling device (7) according to claim 1, characterized by at least one pneumatically or electrically or electromagnetically or hydraulically switchable

Switching valve (23).

3. Cooling device (7) according to one of the preceding claims, characterized by at least one of an outlet nozzle (33) formed coolant outlet (21).

4. cooling device (7) according to claim 3, characterized

in that at least one outlet nozzle (33) has an exchangeable nozzle tip (33.1).

5. Cooling device (7) according to one of the preceding claims, characterized in that with each

Switching valve (23) exactly one Kühlmitteleinzelstrom (Q) is switched on and off.

6. cooling device (7) according to one of claims 1 to 4, characterized in that with at least one

Switching valve (23) a plurality of Kühlmitteleinzelströme (Q) switched on and off.

7. Cooling device (7) according to one of the preceding claims, characterized by at least one longitudinal row of a plurality of along a transport direction (11) of the strand (9) successively arranged coolant outlets (21).

8. Cooling device (7) according to any one of the preceding claims, characterized by at least one transverse row of a plurality of transverse to a transport direction (11) of the strand (9) juxtaposed coolant outlets (21).

9. Cooling device (7) according to one of the preceding claims, characterized by a

Pressure sensing device (29) for detecting a

Coolant pressure (P) or a flow meter for

Detecting a coolant flow in the

Coolant distribution system (15).

10. A cooling method for secondary cooling of a strand (9) in a strand guide (5) of a continuous casting plant (1) by a cooling device (7) according to one of the preceding claims, the cooling device (7) comprising:

- A coolant distribution system (15) with line segments (17.1 to 17.4) for conducting a coolant (19) and a plurality of the strand guide (5) distributed

Coolant outlets (21) for issuing one each

Coolant single flow (Q) on the strand (9),

Current range (AQ) for a time average (Q) of the Kühlmitteleinzelstroms (Q) is formed by a pulse width modulated control of a switching valve (23),

- And a control circuit (45) for controlling a

Coolant pressure (P) or coolant flow in the

Coolant distribution system (15), characterized by the following method steps:

- Rules of a refrigerant pressure (P) or a

Coolant flow in the coolant distribution system (15),

- driving at least one switching valve (23) for switching on and off of at least one coolant single stream (Q), wherein a threshold current (Q _s ) for time averages (Q) of at least one coolant single stream (Q) and below the threshold current (Q _s ) given current range (AQ),

- wherein in the current range (AQ) lying temporal

Average values (Q) of individual coolant flows (Q) with 0 <Q <Qs are generated by a coolant pressure (P) in the

Coolant distribution system (15) to a constant

Pressure value is set and everyone

Single coolant flow (Q) by a pulse width modulated control of a switching valve (23) with a duty cycle (D) dependent on the mean value (Q) to be generated

is pulse width modulated,

- And being outside of the current range (AQ) lying

Kühlmitteleinzelstrom (Q) with Q> Q _{s are} generated by the switching valves (23) of these Kühlmitteleinzelströme (Q) are opened and the refrigerant pressure (P) or a

Coolant flow in the coolant distribution system (15) with the control circuit (45) on one of the

Coolant single (Q) dependent setpoint is regulated.

11. Cooling method according to claim 10,

characterized in that a plurality

Coolant individual streams (Q) in the current range (AQ) for their time average (Q) are pulse width modulated such that one of all these individual coolant streams (Q) together formed total coolant flow (Q _G ) is constant over time.

12. Cooling method according to claim 10 or 11,

characterized in that a plurality

Coolant individual streams (Q) in the current range (AQ) are pulse width modulated for their time average values (Q) in such a way that a total coolant flow (Q _G ) formed by all these individual coolant flows (Q) is regulated to a desired value, an actual value of the

Coolant total flow (Q _G ) is determined and a

Duty cycle (D) and a period length (T) of a clock period of the pulse width modulation in response to a deviation of the determined actual value are controlled by the desired value.

13. Cooling method according to one of claims 10 to 12, characterized in that a selection of

Coolant outlets (21) through which

Coolant streams (Q) are output, depending on a width of the strand (9) is taken.

14. Cooling method according to one of claims 10 to 13, characterized in that a coolant pressure (P) detected in the coolant distribution system (15) and for determining a degree of clogging at least one

Coolant outlet (21) is evaluated.

15. Cooling method according to one of claims 10 to 14, characterized in that the clock frequency f = 1 / T is set in proportion to the casting speed of the continuous casting.

16. Cooling method according to claim 15, characterized

characterized in that the duty D held constant at different casting speeds and the

Coolant single flow (Q) through a

Coolant outlet (21) is set in proportion to the casting speed.

17. Cooling method according to claim 15, characterized in that the duty D held constant at different casting speeds and the

Coolant pressure (P) proportional to the square of the

Casting speed is set.

18. Cooling method according to one of claims 10 to 17, characterized in that the coolant pressure (P) or the coolant flow in the coolant distribution system (15) is adjusted such that in the coolant outlet (21) sets a turbulent flow with Re> 2300.