JP6400830B2 - Cooling of metal strand pieces - Google Patents

Description

  The present invention relates to a method for cooling a strand piece of a metal strand described in the writing of claim 1 and a cooling device described in the writing of claim 14.

  During continuous casting of metal, the metal melt is fed into a normally oscillating water-cooled mold, in which at least the peripheral part solidifies, generally continuously, already in the shape of a strand. From the mold, it is supplied to the strand guiding device arranged downstream of the mold of the continuous casting machine, and is conveyed through the strand guiding device.

  In that case, it is necessary to further cool the strands in the strand guiding device by a cooling device, generally by spraying a coolant on the strands.

  From Patent Document 1, a method for cooling a metal strand is known. In this method, a coolant is sprayed onto the strand from a plurality of cooling nozzles arranged along the strand conveying device. In order to cool a strand based on the said method, patent document 1 has proposed the cooling device which has a switching valve and a cooling nozzle.

  In continuous casting, the strands are generally cast continuously, and the strands that form seamlessly between the start and end of casting typically reach the length of the slab only after continuous casting. The concept of “strand pieces”, as they are cut, also includes areas of strands that are formed seamlessly and that are conveyed at the casting speed through a continuous casting machine cooling device (also called a cooling zone). Should be. It is in no way important for the present invention that the strands are already cut off before cooling in the cooling device. Typically, the strand pieces are simply “virtual pieces” of metal strands that are transported through a continuous caster cooling system at the casting rate.

International Publication No. 2012/163878

  An object of the present invention is to achieve reliable and effective cooling of strand pieces of metal strands. A further problem is to reduce undesirable surge pressure in the conduit of the cooling zone or in the coolant supply conduit to the cooling zone.

  This problem is solved by a method having the features of claim 1 and a cooling device having the features of claim 14.

  Suitable aspects and advantages of the invention will be apparent from the further claims and the description and relate to a method and a cooling device.

  In the method according to the invention for cooling strand pieces of metal strands in a cooling area of a continuous casting machine with a cooling device each having a plurality of switching valves and cooling nozzles, the strand pieces are cooled for cooling purposes. The switching valve is actuated by a binary pulse width modulation control signal, whereby the coolant flow is alternately discharged or blocked through the cooling nozzle, so that the coolant is cooled for cooling. Intermittently sprayed onto strand pieces of the cooling region, the method comprising: a binary pulse width modulation control signal wherein at least one of the plurality of control signals is another control of the plurality of control signals; It is specified that it is determined to have a phase shift with respect to the signal.

  In prior art cooling methods using diverter valves, the spraying density of the coolant may unintentionally be affected by undesired fluctuations in the coolant flow rate, particularly in the chiller conduit or supply conduit. . Such fluctuations can be caused by surge pressure in the coolant, but on the other hand, the surge pressure can be caused by intermittent switching, that is, opening and closing of the switching valve. The height of the surge pressure and thus the magnitude of the variation can be reduced by determining the control signal in accordance with the present invention.

  According to the results of the applicant's investigation, the phase shift results in a time-shifted switching of the switching valve operated on the one hand by the phase-shifted control signal, and on the other hand, this time shift reduces the surge pressure. Thus, equalization of the coolant flow rate through the open cooling nozzle is provided. In this way, it is possible to counter the undesirable effects of coolant spray density by easy means. The method according to the invention, in particular the determination of the control signal as described above, is that the strand pieces transported through the cooling zone are sprayed at the end of the cooling zone with substantially the same coolant spreading density through the strand pieces. to enable.

  That is, reliable and effective cooling of the strand pieces is obtained in particular by reducing undesirable surge pressures in the cooling zone conduit or in the coolant supply conduit to the cooling zone.

  The present invention starts with the recognition that when transporting a strand through a cooling zone, heat conduction from within the strand results in reheating of the strand surface at various strengths first along the strand. Yes. Therefore, it is desirable that the cooling performance can be changed along the strand or the cooling device. Otherwise, strand supercooling can occur with metallurgical degradation. In this connection, on the one hand, it is advantageous to apply the coolant to the strands intermittently, ie with a temporal interruption. In this way it is possible to set the amount of coolant and thus the cooling performance over a wide range of values in an easy, stable and energy efficient manner. On the other hand, in the case of intermittent coolant spraying, it is discontinuous in itself and even coolant spraying cannot be easily guaranteed. This is because an undesirable interaction can occur between the time interruption of coolant application and another process variable of the continuous casting process. For example, if a strand piece is transported through a cooling area, partially or completely, during a time interruption of coolant application, or even in the event of a failure such as a cooling nozzle, the strand piece is , Unintentionally, there is insufficient cooling or no cooling at all. This can again be accompanied by undesirable strand degradation. Such undesirable lack of cooling or quality degradation can be avoided if an even coolant distribution density occurs on the strand pieces in the sense of the amount of coolant per unit area. In doing so, it is important to realize that an even coolant distribution density can occur at the latest by the time the strand pieces are conveyed through the cooling zone, i.e. by the end of the cooling zone. According to the invention, the control signal is determined such that the above-mentioned drawbacks of intermittent coolant application are overcome. In simplified terms, the time interruption of coolant application to the strands is intentionally adjusted so that the above-mentioned drawbacks of intermittent coolant application are overcome.

  The strand pieces may be portions of the strands in the longitudinal direction of the strands or in the transport direction of the strands through the cooling region. In particular, the strand can be formed of a plurality of strand pieces, at least for the most part in its entire length. The division of a strand into a plurality of strand pieces can simply be a virtual division of a quasi-continuous strand, i.e. a strand that continuously extends as one piece and extends over at least half the length of the strand guide device.

  The metal strands can at least mostly comprise steel or can be steel strands.

  A cooling region in the sense of the present invention can be a region through which strand pieces or strands are transported and passed for spraying of coolant. Suitably, the cooling zone is arranged along the strand guiding device of the continuous casting machine, preferably in the region of the strand guiding device. The continuous casting machine may comprise a plurality of cooling zones, in particular arranged continuously in the direction of strand transport. For example, the cooling area can be an area that can be wetted by the coolant discharged from the cooling nozzle.

  Intermittent spraying of the coolant is realized by repeatedly switching between the open state and the closed state of the switching valve. Suitably, the switching valve is arranged upstream of the cooling nozzle in the flow direction of the coolant.

  Suitably, the switching valve is actuated by a binary control signal. Binary means that the control signal can assume two states, in particular 0 or 1, or HIGH or LOW.

  Advantageously, each switching valve is actuated by a control signal. In other words, preferably each switching valve is actuated by a unique control signal. However, it is also conceivable to operate one group of switching valves, in particular simultaneously, with one and the same control signal.

  The switching valve can still discharge or block the coolant flow with a single cooling nozzle. However, it is also conceivable for multiple coolant flows through one group of multiple cooling nozzles to be released or blocked by one and the same switching valve.

  Advantageously, the binary control signal is a pulse width modulation control signal, the signal technology characteristics of which can be determined by carrier frequency, pulse width ratio, phase shift, etc.

  In the sense of the present invention, determination means that a signal technology characteristic of at least one control signal, for example the carrier frequency, is modulated or adapted or changed. In other words, the control signal is a modulation of at least one of its signal technology characteristics, in particular its respective carrier frequency, its respective pulse width ratio, and / or its respective further control. It can be determined by modulation of the phase shift on the signal. This determination is advantageously made in response to at least one state variable, which may be a state variable of a continuous casting process (eg casting speed), a strand, a cooling device, etc.

In the sense of the present invention, the coolant spreading density can be understood as the unit quantity of coolant relative to the unit area of the strand pieces. Suitably, the coolant spray density is the amount of coolant per unit area and can be expressed in units of measurement, for example 1 / m ² .

  The invention advantageously specifies that the temporal interruption of intermittent coolant application to the strand pieces in the cooling zone is adjusted by modulation of the control signal, i.e. by changing the signal characteristics. The surface of the strand piece to be cooled will experience the same cooling performance by the action of the coolant at every position after passing through the cooling zone.

  In order to determine the temporal interruption, the control signal, i.e. its characteristics, the transport speed of the strand and / or the error condition of the cooling device and / or the geometric characteristics of the cooling area and / or two cooling nozzles or two It is advantageous to determine using the distance between the cooling nozzle rows.

  In this way, it is possible to obtain an even coolant distribution of the strands and thus an even metallurgical quality of the strands, in particular while protecting the known advantages of intermittent coolant distribution. .

  For detection of an error condition of the cooling device, advantageously, a state variable representing the physical state of the coolant is present, in particular in the region of the coolant supply conduit common to at least a plurality of switching valves and / or a plurality of cooling nozzles. Detected. Furthermore, it is advantageous to compare the transition of the state variable with the reference transition. Preferably, based on the comparison, an error state of at least one switching valve of the plurality of switching valves and / or at least one cooling nozzle of the plurality of cooling nozzles of the cooling device is detected.

  In addition to determining whether a cooling device error or failure exists, the detection of a cooling device error condition can also determine which element of the cooling device has failed, i.e., the cooling device has failed Identification of the position of the element can also be included.

  Suitably, the control signal is at least temporarily compensated for error conditions, preferably by modulation of at least one of its signal technology characteristics, preferably without undesirably affecting the quality of the strand. To be determined.

  In this way, it is possible, for example, to delay the replacement of a defective switching valve and / or a defective cooling nozzle in time and to reduce the downtime during which no continuous casting machine is produced. .

  Error condition compensation means that even if an error condition exists, the control signal is determined or adjusted so that the strand pieces are distributed at the end of the cooling region and are distributed at approximately the same coolant distribution density through the strand pieces. Can mean that. That is, properly, when compensating for error conditions, the control signal is applied across the strand pieces at the end of the cooling zone with the same or approximately the same coolant distribution density as when no cooling device error conditions existed. Determined or adjusted as it is sprayed. That is, suitably, the effects of error conditions are compensated.

  The detection of an error condition is based on the recognition that a cooling device for spraying coolant can be at least partially disturbed by errors in its function. In order to counter the undesirable effects of such error conditions on the even distribution of coolant to the strand pieces, it is desirable to be able to reliably recognize the error condition of the cooling device. The error condition of the cooling device can be due in particular to one or more switching valve failures and / or one or more cooling nozzle failures. For example, one and / or more switching valves can no longer be switched from an open state to a closed state and / or vice versa as a result of blocking, i.e. blocking. Has been. Furthermore, one switching valve and / or one cooling nozzle may be at least partially blocked. In addition, each of the plurality of switching valves and / or the plurality of cooling nozzles may be at least partially blocked. What is important here is the recognition that the position of the failed switching valve and / or the failed cooling nozzle must be clearly identified. Thereby, the determination of the control signal is adjusted according to the method, and even if such an error condition exists, a uniform coolant distribution density is obtained. At that time, detecting an error state for each switching valve and / or cooling nozzle by a sensor is expensive and easily causes an error. This is because a plurality of sensors are necessary. A state variable representing the state of the coolant is detected in the region of the coolant supply conduit common to at least a plurality of switching valves and / or at least a plurality of cooling nozzles, thereby reducing the measurement technical costs associated with detecting an error condition. Can be reduced. That is, in a simplified manner, a plurality of sensors are arranged at a plurality of positions of the cooling device and a plurality of measured values are not obtained, but one sensor is arranged at the cooling device and a measured value is obtained.

  The state variables are in particular coolant state variables, and can be, for example, pressure, acceleration, sound pressure, flow rate, and the like.

  Suitably, a state variable in a coolant supply conduit that supplies coolant to a plurality of switching valves and / or a plurality of cooling nozzles is detected.

  The state variables can be detected during normal operation of the cooling device, i.e. during strand production and / or during cooling device maintenance operations.

  The reference transition is a transition of the detected state variable through time, frequency, etc., and the transition is detected or detected when there is no error in the function of the cooling device.

  The comparison can be performed by mathematical operations taking into account the reference transition and the transition of the state variables. The comparison can be done by determining the difference between the state variable transition and the reference transition.

  The cooling device according to the present invention includes a switching valve, a cooling nozzle, a coolant, and a control device for cooling the metal strand pieces in the cooling region of the continuous casting machine. The control device has a binary pulse width. The modulation control signal is determined and adjusted to operate the switching valve using the control signal, and the control device is adjusted to determine the phase shift of one control signal of the plurality of control signals. ing.

  The invention departs from the recognition that measurement techniques and / or control techniques are necessary for reliable and effective cooling of the strand pieces. The invention makes it possible to carry out these means according to the method by having the control device set in this way.

  Preferred further embodiments of the invention emerge from the dependent claims. These further aspects relate both to the method according to the invention and to the cooling device according to the invention.

  Preferably, the cooling device according to the invention is set up to carry out at least one of the methods according to the invention, in particular the further aspects of the method according to the invention described below.

  Furthermore, the cooling device may have a measuring device and / or a detecting device.

  Advantageously, the measuring device comprises a sensor, which is a state variable representing the state of the coolant in the region of the coolant supply conduit common to at least the plurality of switching valves and / or at least the plurality of cooling nozzles It has been adjusted to detect.

  In one advantageous aspect of the cooling device, the detection device is adjusted to compare the transition of the state variable with a reference transition and detect an error state of the cooling device based on the comparison.

  Preferably, the controller provides the binary pulse width modulation control signal so that the strand pieces transported through the cooling zone are spread at the end of the cooling zone with substantially the same coolant spreading density through the strand pieces. It has been adjusted to be determined.

  The invention and the further aspects described can be implemented in software and hardware, for example using special electrical circuits.

  Furthermore, the present invention or the described further aspects can be realized by a computer-readable storage medium in which a computer program for executing the present invention or the further aspects is stored.

  Each of the present invention and / or the further aspects described may also be realized by a computer program product having a storage medium having stored thereon a computer program for executing the present invention and / or further aspects. Yes.

Assuming that each of the n switching valves is operated with the same characteristics such as the carrier frequency F and the pulse width ratio κ, each with one control signal, the phase shift φ is a simple equation such as φ = t _p / n may be determined by this time, t _p is the cycle length of the control signal, i.e. the inverse of the carrier frequency F.

  In particular, if the control signal has various carrier frequencies and / or pulse width ratios, it may be necessary to deviate from a simple calculation for the determination of the control signal.

  In a further aspect, the phase shift of one of the plurality of control signals is determined using a numerical optimization process to minimize coolant volume flow fluctuations.

  The volume flow variation can represent a variation in the coolant flow rate through the chiller conduit or supply conduit.

  For the optimization process, the frequency spectrum of the volume flow can be detected. The frequency spectrum can be divided into constant terms (Term) and trigonometrisch terms. The trigonometric term may depend on the pulse width ratio and phase shift of the control signal. Given the pulse width ratio of the control signal, the optimization may be directed to adjusting the phase shift.

  The optimization process can be performed by so-called genetic algorithms, gradient-based methods and the like.

  According to a preferred further aspect, at least two control signals having different carrier frequencies are determined.

  The carrier frequency can be the reciprocal of the time between switching the two states of the control signal, respectively from LOW to HIGH and / or from HIGH to LOW, respectively. A relatively high carrier frequency can result in coolant spraying that is intermittently relatively fast. In other words, the carrier frequency can be the reciprocal of the period length of the control signal period.

  At least two control signals can each actuate one switching valve, each switching valve discharging and / or blocking the coolant flow through the cooling nozzle, respectively. In this way, different amounts of coolant can be spread on the strands through the cooling nozzles thus directed. Dispersing different amounts of coolant in this way, especially in various regions of the cooling device, preferably in continuous regions in the direction of strand transport, can be advantageous in order to obtain the same coolant spray density through the strand pieces. .

  If there is an adverse interaction between the carrier frequency and thus the time interruption of the coolant spray and the process technical variables of the continuous casting process and / or the parameters of the continuous caster, the coolant spray density is undesirable. Impact can occur.

  Thus, in a particularly advantageous further aspect, the carrier frequency of one control signal of the plurality of control signals is determined as a function of the speed of the strand pieces.

  Even when the strand speed or the casting speed is changed by such a method, a uniform coolant spray density can be obtained.

  In addition, it is advantageous if the carrier frequency of one control signal of the plurality of control signals is determined according to the length of the cooling zone.

  The length of the cooling region can be an extended portion of the cooling region generally along the strand transport direction. The length of the cooling region may be the length of the region where the coolant is sprayed through the cooling nozzle.

  Since the cooling device can include cooling zones having various lengths, an even coolant distribution density can be obtained in this way, especially under such circumstances.

  Furthermore, it is advantageous if the carrier frequency of one of the plurality of control signals is determined in accordance with the region in which the coolant can be distributed through the cooling nozzle, in particular the transit time of the strands through the cooling region.

  The transit time can be a quotient of the length of the cooling zone and the strand speed.

  Furthermore, it is advantageous if the carrier frequency of one control signal of the plurality of control signals is determined according to the spray profile of the cooling nozzle.

  The spray profile can be a progression of the coolant distribution density that can be obtained along the surface that is wetted using the cooling nozzle.

  A rectangular spray profile is conceivable, where the same amount of coolant is sprayed along the surface at any wetted point.

Particularly when a rectangular spray profile is present, it is advantageous if the reciprocal of the carrier frequency F, ie the period length t _{p of the} control signal, is determined according to the equation t _p = x _n / (k * v), , X _n is the length of the cooling zone, k is a positive integer (1, 2, 3,...), And v is the strand velocity.

  Also conceivable is a triangular spray profile, in which the coolant spray density increases linearly from minimum to maximum along the surface to be sprayed and then again linearly to minimum. Decrease.

Particularly when a triangular spray profile is present, it is advantageous if the reciprocal of the carrier frequency F, ie the period length t _{p of the} control signal, is determined according to the equation t _p = x _n / (g * v), , X _n is the length of the cooling zone, g is a positive even number (2, 4, 6,...), And v is the strand velocity.

  Advantageously, the phase shift of one control signal of the plurality of control signals is determined according to the speed of the strands and / or the length of the cooling zone and / or the spray profile of the cooling nozzle.

  Furthermore, it is advantageous if the pulse width ratio of one control signal of the plurality of control signals is determined according to the speed of the strands and / or the length of the cooling zone and / or the spray profile of the cooling nozzle. It is.

  By determining one or more control signals in the manner as described above, the spraying of the coolant on the strand pieces is performed at approximately the same coolant spray density through the strand pieces after passing through the cooling zone. It becomes feasible.

  In an advantageous embodiment, at least two control signals having different pulse width ratios are determined.

  The pulse width ratio can express the relative ratio of the control signal pulse, that is, the period of the control signal transition in the binary high state. For example, a pulse width ratio of 100% represents a control signal having a permanent state of 1 or HIGH. For example, a pulse width ratio of 50% represents a control signal having a rectangular profile, each rectangular pulse lasting half the period length.

  In order to compensate for the amount of coolant that has not been sprayed due to errors such as, for example, a failure of the cooling nozzle, it is advantageous if an additional amount of coolant is sprayed onto the strands by further cooling nozzles.

  Therefore, it is particularly advantageous if the pulse width ratio of one control signal among the plurality of control signals is determined according to the error condition of the cooling device.

  Further, a phase shift of one control signal of the plurality of control signals with respect to another control signal of the plurality of control signals is determined according to an error condition of the cooling device and / or the plurality of control signals. Advantageously, the carrier frequency of one of the control signals is determined according to the error condition of the cooling device.

  For example, if an error condition occurs in the form of a cooling nozzle failure, the pulse width ratio of the control signal is changed to activate another cooling nozzle, thereby the amount of coolant that was not sprayed due to the error Is additionally sprayed on the strands by this further cooling nozzle. In this way, it is possible to counter the undesirable coolant dispersion of the strands which is undesirably uneven due to errors.

  As long as the casting speed is particularly high or the length of the cooling zone is particularly small, as long as the coolant is sprayed on the strand by only one coolant nozzle or by a row of coolant nozzles in the cooling zone, An equal coolant spray density is not easily obtained.

  In a further advantageous embodiment, the method is used for cooling strand pieces in a cooling zone, in which at least two cooling nozzles are arranged in succession in the conveying direction of the strand pieces. In this way, compensation of the amount of coolant can be done in an easy way through more than one cooling nozzle (cooling nozzle row).

  According to a preferred aspect, using the transition of the state variable, the frequency spectrum of the state variable is detected and compared with a reference frequency spectrum.

  The transition of the state variable can be a transition of time, in particular a transition of pressure over time. The frequency spectrum can be detected by a technique such as so-called fast Fourier transform. The reference frequency spectrum is a frequency spectrum detected or detected when the cooling device is functioning without causing an error.

  Due to intermittent coolant discharge, actuating and switching the switching valve results in a sudden change in the state variable of the coolant in the coolant supply conduit, i.e. a sudden change in the state variable over time. obtain. Such a sudden change may have a frequency spectrum with an excessive rise in frequency, i.e. peaks. In doing so, switching of the plurality of switching valves may result in a plurality of characteristic frequency peaks within the frequency spectrum, with each peak being directed to the respective switching valve and / or cooling nozzle. Can be assigned. Thus, by comparing with the reference spectrum, the failed switching valve and / or the failed cooling nozzle can be easily detected and the position thereof can be specified.

  In addition, it is advantageous to activate at least one switching valve with a control signal having a temporarily increased switching test frequency during detection of the state variable.

  Suitably, the frequency spectrum of the state variable is detected. When the switching test frequency is not included in the frequency spectrum as a characteristic frequency peak, an error condition is estimated in the switching valve operated at the switching test frequency and / or the cooling nozzle disposed downstream of the switching valve. Can be done.

  Suitably, the plurality of switching valves supplied by a common coolant supply conduit operate at a switching test frequency in succession, preferably for 2 to 4 seconds each. Advantageously, the switching test frequency exceeds the general switching frequency or carrier frequency of the switching valve by at least twice. In this way, the error condition can be detected while avoiding the influence of the coolant spray density during the steady operation of the cooling device.

  According to one preferred aspect, the state variable is detected by a pressure sensor. The pressure sensor has been tested many times and is available in a number of embodiments adapted to each application. With such a method, the state variable can be detected reliably and inexpensively.

  In an advantageous implementation variant, the state variable is detected by a flow sensor. Often, a flow sensor for detecting coolant consumption is not a component of a cooling device, so that state variables can be detected particularly inexpensively.

  In another advantageous implementation variant, the state variable is detected by an acoustic sensor. The sound can then be detected directly, for example, in the coolant supply conduit or indirectly at another point in the cooling device, so that the introduction of a sensor system into the coolant flow can be avoided. In this way, it is possible to detect state variables particularly flexibly locally.

  Advantageously, the state variable is detected with an acceleration sensor. Accelerometers have been tested many times and are available in a number of embodiments adapted to each application. With such a method, the state variable can be detected reliably and inexpensively.

  In an advantageous embodiment of the invention, the method according to the invention, in particular one of the further embodiments described above, is used in one of the cooling zones of a continuous caster. In this context, the expression “in one of the cooling zones” means “in just one of the cooling zones” or “only one of the cooling zones”. Can be understood as. Furthermore, the method according to the invention, in particular one of the further aspects described above, can be used in each of the cooling zones of a continuous casting machine.

  According to a preferred embodiment, the detection device is tuned to detect the frequency spectrum of the state variable, preferably using the temporal transition of the state variable.

  Furthermore, it is advantageous if the detection device is tuned to compare the frequency spectrum of the state variable with a reference frequency spectrum.

  Furthermore, it is advantageous if the detection device is adjusted to detect a failed switching valve and / or cooling nozzle by comparison.

  Furthermore, it is advantageous if the control device is adjusted to determine the carrier frequency of one control signal of the plurality of control signals.

  Furthermore, it is advantageous if the control device is adjusted to determine the pulse width ratio of one control signal of the plurality of control signals.

  Furthermore, it is preferred if the cooling device is tuned to determine at least two control signals having different carrier frequencies and / or pulse width ratios.

  It is particularly preferred that the cooling device is tuned to determine at least one control signal of the plurality of control signals to have a phase shift with respect to another control signal of the plurality of control signals.

  Advantageously, the controller is adjusted to determine one phase shift of the plurality of control signals in one of the plurality of cooling zones of the continuous caster. In this context, the expression “in one of the cooling zones” means “in just one of the cooling zones” or “only one of the cooling zones”. Can be understood as. Further, the control device may be adjusted to determine a phase shift of one control signal among the plurality of control signals in each of the plurality of cooling regions of the continuous casting machine.

  The advantageous embodiments described so far include a number of features, which are partly expressed in a plurality of features in the respective subclaims. However, these features can be considered individually and appropriately, and can also be combined into meaningful combinations. In particular, it is possible to combine these features individually and in any suitable combination with the method according to the invention and the device according to the invention as described in the independent claims.

  The characteristics, features, and advantages of the present invention described above, and methods for obtaining them will become apparent and can be clearly understood in the context of the detailed description of the embodiments using the following drawings. . The examples are used to describe the present invention, and the present invention is not limited to the combination of features described in the description of the present invention, nor is it limited in terms of functional features. In addition, the features of each embodiment suitable for it can be considered clearly separated, separated from one embodiment, introduced into another embodiment for its supplement, and / or optional It can also be combined with the claims.

It is the schematic of the cooling device which has the switching valve and cooling nozzle for cooling a metal strand piece. It is the schematic of the binary pulse width modulation control signal for operating the switching valve which concerns on FIG. FIG. 3 is a diagram for clarifying the relationship between the coolant spray density and the determination of the control signal according to FIG. 2. It is a figure similar to FIG. 3 in case the spray profile of a cooling nozzle is a triangle in the conveyance direction of a strand piece. It is a figure which shows the frequency spectrum of the coolant pressure at the time of switching one switching valve among the switching valves concerning FIG. It is a figure of the frequency spectrum which concerns on FIG. 5 at the time of switching a some switching valve. It is the figure which compared two frequency transition when an error state exists in one of the some switching valve and / or cooling nozzle which concern on FIG. It is a figure which shows a time-dependent pressure transition when the switching valve which concerns on FIG. 1 act | operates with a switching test period. FIG. 2 is a schematic diagram of an optimization process for minimizing variation in the coolant volumetric flow rate in the coolant supply conduit according to FIG. 1. FIG. 2 is a schematic diagram of an optimization process for minimizing variation in the coolant volumetric flow rate in the coolant supply conduit according to FIG. 1. FIG. 2 is a schematic diagram of an optimization process for minimizing variation in the coolant volumetric flow rate in the coolant supply conduit according to FIG. 1.

  FIG. 1 schematically shows a cooling device 2 for cooling metal strand pieces 4 in a cooling zone 6 of a continuous casting machine. The continuous caster is not shown for clarity of illustration.

  The cooling device 2 includes a switching valve 8, a cooling nozzle 10, a coolant supply conduit 14 that guides the coolant 12, a measurement device 16, a detection device 18, and a control device 20. In this embodiment, each switching valve 8 is disposed upstream of each cooling nozzle 10. Obviously, it is also conceivable that a plurality of cooling nozzles, for example so-called cooling nozzle bars, are directed through the respective switching valves.

The cooling region 6 has a length L and includes six cooling nozzles 10 arranged in series. But also, the cooling region, the cooling nozzle 10 includes only one, it is also possible to have a length L _1.

  The measuring device 16 has a sensor 24 disposed in the coolant supply conduit 14 or the measurement location 22, which is tuned to detect the transition of state variables representing the state of the coolant 12. Yes. In this example, the state variable is the pressure 26 of the coolant 12 at the measurement location 22.

  The detection device 18 is adjusted so as to compare the transition of the pressure 26, the transition of time and / or frequency, etc. with the reference transition and detect the error state of the cooling device 2 based on the comparison.

  The control device 20 determines the binary pulse width modulation control signal (see FIG. 2: 38, 40, 42, 44) and is adjusted to operate the switching valve 8 by the control signal passing through the signal line 28. .

During the continuous casting process, the strand piece 4 is guided between the strands induced roll 30, for cooling, in the transport direction 32, which is also the casting direction, at a velocity v, over the length L, which is also considered as L ₁ It is conveyed through the extended cooling region 6 and passes near the cooling nozzle 10.

  In so doing, the switching valve 8 is actuated by a binary pulse width modulation control signal (see FIG. 2), respectively, through the control device 20, whereby the coolant flow is alternately discharged or blocked through the cooling nozzle 10. , Whereby the coolant 12 is intermittently applied to the strand pieces 4 in the cooling zone 6 for cooling. Each cooling nozzle 10 has a triangular spray profile 34 in the transport direction 32.

  The binary pulse width modulation control signal is generated by the control device 20 so that the strand pieces 4 conveyed through the cooling region 6 are dispersed at the end 36 of the cooling region 6 through the strand pieces 4 with substantially the same coolant distribution density. To be determined.

Particularly evident from the drawings, in the prior art, even coolant spreading of the strand pieces 4 is not easily possible due to intermittent coolant spreading. If the control signal is determined in an unfavorable manner, depending on the speed v, the length L or L ₁ , the failure of one of the switching valves 8 and / or the cooling nozzle 10, etc. While the coolant spraying is interrupted in time, the coolant 12 is transported and passed under the cooling nozzle 10 without spraying the coolant 12. According to the prior art, this can result in an uneven coolant distribution density through the strand pieces 4 at the end 36 of the cooling zone 6 which is undesirable.

  The method is used for cooling the strand equipment having the shape of a long product, specifically a so-called beam, blank, bloom, billet, round, etc. It is not limited to suitable cooling equipment. Other cooling equipment, such as cooling equipment for cooling the slab, can be operated after the cooling process as well.

  FIG. 2 schematically shows an exemplary change over time of the binary pulse width modulation control signals 38, 40, 42 and 44 for operating the switching valve 8 according to FIG. . The figure shows the characteristics that can be adjusted or modulated for the determination of the control signal, ie period length, pulse width ratio and time offset (phase shift).

  From FIG. 2 it can be seen that the control signals 38 to 44 alternate between 1 or HIGH and 0 or LOW, respectively, over time t in the signal state u shown on the ordinate, ie, signal technology. It is clear that it is binary in this sense.

Control signal 38 is determined by the period length _{t p} and the pulse width ratio _{κ = t 1 / t p,} t 1 is the pulse length. Reciprocal 1 / _{t p} of the period length is the carrier frequency F of the control signal 38.

  At this time, the higher the carrier frequency F, the shorter the switching cycle between the open state and the closed state of the switching valve 8 operating in this way, and a plurality of cooling nozzles 10 arranged downstream of the switching valve. The time interruption of the coolant application to the strand pieces 4 through one and / or a plurality of cooling nozzles 10 is shortened.

Control signal 40 is determined by twice the period length 2 * t _p in comparison with the control signal 38, i.e. a carrier frequency F / 2. At this time, the absolute pulse widths of the control signals 38 and 40 are the same, but the pulse width ratio of the control signal 40 is κ / 2. As a result, when the switching valve is operated by the control signal 40, only half the amount of coolant is sprayed within the switching period as compared to the operation by the control signal 38.

Control signal 42, as compared with the control signal 40 has the same period length 2 * t _p. At that time, absolute pulse width because it is _t 1/2, the pulse width ratio of the control signal 42 is a _{κ / 4 = (t 1/} 2) / (2 * t p).

Control signal 44, as compared to the control signals 38, 40, and 42 are determined to have a time delay t _z, therefore, have a phase shift.

FIG. 3 is a diagram for clarifying the relationship between the coolant spray density and the determination of the control signal using the signal characteristics shown in FIG. In particular, FIG. 3 shows the state (ordinate, u) of the control signal 46 over time (abscissa, t). The control signal 46 is determined by the pulse length t ₁ and the period length t _p = 2 * t ₁ , that is, has a pulse width ratio of κ = 50%.

  In doing so, the curve of the control signal 46 corresponds to the average coolant flow q, ie the average amount of coolant per unit of time, which is discharged into the cooling zone through the cooling nozzle operated indirectly by the control signal 46. doing. Furthermore, the surface surrounded by the curve 46 up to time t corresponds to the amount of coolant released up to that point.

Some strands piece enters the cooling region at the time of t _10, but leaves the cooling region at the time of t _20, it is sprayed an amount Q of coolant therebetween. At this time, the amount Q of the coolant sprayed on a part of the strand piece corresponds to the area of the hatched portion below the curve 46 surrounded by the region 48 indicated by the broken line.

Is clearly shown by the region 50, another portion of the strand piece, enters the cooling zone at time t _30, when leaving the cooling area at the time of t _40, the corresponding portion, the same amount Q of coolant Is sprayed.

Both parts of the strand pieces pass through the cooling region with the same transit time t _n , ie have the same length or area when the velocity v is assumed to be the same, and the same amount Q of coolant. Is sprayed. Thus, the strand pieces formed by both regions 48 and 50 conveyed through the cooling region have a uniform coolant distribution density at the end of the cooling region.

Regions 48 and 50, respectively, mean transit time t _n of the coolant cooling area flow q is sprayed is twice the period length t _p.

The transit time t _n is then determined by the cooling zone length L ₁ and the strand speed v.

  Theoretically, shifting the regions 48, 50 indicated by the dashed lines along the time axis t is equivalent to transporting the strand pieces through the cooling region, which is always indicated by the same diagonal lines. The surface is surrounded, so that an even coolant distribution density is obtained.

By this the is obtained, the period length t _p of the control signal 46, since is determined according to the spray profile 34 of length L ₁ and / or cooling the nozzle 10 of the speed v and / or cooling area of the strand piece 4 is there.

  FIG. 4 shows a situation in the case where the spray profile of the cooling nozzle is triangular in the conveying direction of the strand pieces, similar to FIG. The following description is generally limited to the differences from the embodiment of FIG. 3, which is pointed out with respect to invariant features and functions. In general, members that are essentially unchanged are given the same reference numerals, and features not mentioned are incorporated in the following examples without being newly described.

In particular, FIG. 4 shows the transition of the control signal 52 and the two regions 54 and 56 of the strand piece. Regions 54, 56 of the strand _piece, enters the cooling zone at time _{t 50} or _{t 60,} leaves the cooling region at the time of _{t 70} or _{t 80,} it is sprayed with coolant of the same amount Q. Thus, the strand pieces formed by both zones 54 and 56 conveyed through the cooling zone have a uniform coolant distribution density at the end of the cooling zone. For that purpose, it is important that the period length t _p is an even multiple of the transit time t _n .

  FIG. 5 is a diagram showing the frequency spectrum of the pressure of the coolant 12 in the supply conduit 14 of the cooling device 2 according to FIG. 1 when one of the plurality of switching valves 10 is activated (ordinate: p (bar)). , Abscissa: f (Hz)). The pressure p (or 26, see FIG. 1) can be detected by the sensor 24 of the measuring device 16. The frequency spectrum is detected by a detection device 18 (see FIG. 1) from the time course of pressure using here a so-called FFT analysis (Fast Fourier Transform). It is also possible to perform so-called partial FFT analysis, i.e. fast Fourier transform for a specific frequency domain.

  The frequency spectrum has a resonance peak 58 at a frequency f of about 75 Hz. The resonance peak 58 is caused by a surge pressure in the coolant supply conduit 14 due to switching of one of the switching valves 10.

  FIG. 6 is a diagram showing a frequency spectrum of the coolant pressure when a plurality of switching valves 10 are operated (right abscissa: number of valves n (−)) (ordinate: p (bar), left abscissa). Coordinate: f (Hz)). The coolant pressure p is again detected at the measurement location 22.

  The frequency spectrum has a resonance peak 60 at a frequency f of about 75 Hz. In this case, the magnitude of the resonance peak 60 increases through the number n of valves.

  This increase can be explained by the distance to the measurement point that exists in this example and increases as the number of valves increases, thereby increasing the hydraulic inductance and causing a higher pressure peak in the coolant 12. Be triggered.

  In order to detect an error condition in the cooling device 2, in particular the switching valve 8 and / or the cooling nozzle 10, the transition of the frequency spectrum, in particular the resonance peak 60, is compared by the detection device 18 with a reference transition.

  From the difference between the reference transition recognized by the comparison and the transition of the resonance peak, for example, the degree of clogging of one or more switching valves 8 and / or cooling nozzles 10 can be estimated.

  The advantage of this approach is that errors can be detected continuously, thus online, ie even during the normal continuous casting process.

  FIG. 7 compares the two frequency transitions 62 and 64 of the coolant pressure p when an error condition exists in one of the switching valves 8 and / or the cooling nozzles 10 according to FIG. It is a figure (ordinate: p (bar), abscissa: f (Hz)). The transitions 62 and 64 are then related to the operation of the respective switching valve 10.

  The frequency transition 62 represents a state with no error, that is, a reference frequency transition. The frequency transition 64 occurs, for example, in clogged, non-switchable or otherwise non-switchable switching valves and / or damaged cooling nozzles. By comparing between both frequency transitions 62 and 64, an error condition can be clearly detected.

  FIG. 8 is a diagram (abscissa: t (s)) showing the pressure transition 66 with the passage of time when the switching valve 8 according to FIG. 1 operates in the switching test cycle 68. This is determined by the transition of the control signal over time. In that case, the detection of the error condition can again be performed by comparison with a reference transition or alternatively by comparison between pressure peaks 70.

It is possible to convolve the pressure transition 66 or the signal representing the pressure transition 66 with an appropriate convolution signal. In so doing, the convolution signal may be selected such that amplification and / or noise reduction is as advantageous as possible. For example, the function sin ² (t) may be selected as a convolution signal or function. Furthermore, it is possible to consider the switching valve behavior and the resulting time derivative.

  Advantageously, the switching test cycle is determined to have switching distributed evenly throughout the switching test cycle length.

  FIGS. 9-11 schematically illustrate an optimization process for minimizing the volumetric flow variation of the coolant 12 in the coolant supply conduit 14 according to FIG. By minimizing volume flow fluctuations, it is possible to counter the undesirable effects of coolant spray density.

  If the control signal for actuating the switching valve is determined with the same pulse width ratio, an easy approach can be used:

For example, a variable time delay t _z (see FIG. 2) between spike trains of control signals can minimize the reaction to the upper delivery system, ie volume flow variation: control signal determination With regard to this easy approach to do this, consider, as an example, a group of six switching valves (see FIGS. 1 and 8) having six cooling nozzles 10 placed downstream. The group operates with a carrier frequency F of 1 Hz and the same pulse width ratio κ of 50%. If the switching valves are switched simultaneously, an undesirably large surge pressure is induced in the common coolant supply conduit 14, which can cause volumetric flow fluctuations and therefore undesirable effects of coolant spray density. .

  If the switching valve is operated at different times, for example with a delay of 0.1 seconds each, the undesirable reaction to the system is reduced.

  However, if the control signal for operating the switching valve is determined at various pulse width ratios κ, it is not possible to use this easy approach and the control signal illustrated in FIGS. It is advantageous to use an optimization process to determine

  To that end, the frequency spectrum of the flow rate or volume flow rate of the coolant 12 through the coolant supply conduit 14 is detected. The frequency spectrum can be detected, for example, from the pressure p of the coolant 12 detected by the sensor 24 of the measuring device 16 for indirect detection of the volume flow, or directly and subsequent detection of the volume flow. Can be performed by FFT using the apparatus 18.

  It is possible to detect the frequency spectrum using a simulation technique, for example a so-called prior simulation. For this purpose, it is advantageous to use a general simulation tool.

Frequency spectrum of the flow A is divided into a section of constant section and trigonometry, terms of trigonometry, it depends on the time delay t _z pulse width ratio κ and switching.

FIG. 9 shows the result of this decomposition when switching two switching valves on a complex plane 72 (abscissa: real part Re, ordinate: imaginary part Im) as a phase vector (Zeigerschreibweise). At that time, the values of the flow rates A ₁ and A ₂ depend on the respective pulse width ratios κ of the control signals for operating the respective switching valves. Phase shift phi ₁ or phi ₂ is dependent on the respective time delay _{t z.}

At that time, the resulting must minimize the phase vector 74 with quantitative total flow A _v.

FIG. 10 shows the result of optimization in the exemplary case where 10 switching valves are operated by 10 control signals having the same pulse width ratio κ. This optimization results in the flow rates A ₁ to A ₁₀ being rotated by a phase shift 76 (Δφ), also optimized in the 10 complex plane. Optimization may be performed by genetic algorithms, gradient-based optimization methods, and the like. Is the cost function being optimized, the cost function is summed across all considerations are Fourier terms it was, can be represented by the sum of the absolute value of the square of the complex phasor A _v.

  FIG. 11 is an alternative diagram showing the result of optimization.

DESCRIPTION OF SYMBOLS 2 Cooling device 4 Strand piece 6 Cooling area 8 Switching valve 10 Cooling nozzle 12 Coolant 14 Coolant supply conduit 16 Measuring device 18 Detection device 20 Control device 22 Measuring location 24 Sensor 26 Pressure 28 Signal line 30 Strand guide roll 32 Transport direction 34 Spray profile 36 End of cooling region 38, 40, 42, 44 Control signal 46 Control signal 48, 50 region 52 Control signal 54, 56 region 58, 60 Resonance peak 62 Reference frequency transition 64 Frequency transition 66 Pressure time transition 68 Switching test Period 70 Pressure peak 72 Complex plane 74 Resulting phase vector 76 Optimized phase shift t time t ₁₀ , t ₂₀ , t ₃₀ , t ₄₀ time point t ₅₀ , t ₆₀ , t ₇₀ , t ₈₀ time point t _n transit time slow t _p cycle length t ₁ pulse length t _z time u signal state v velocity κ pulse width ratio φ, φ _1, φ ₂ phase shift Δφ optimized phase shift A ₁ from _{A 10} coolant flow A _v resulting coolant flow F carrier frequency L, _{L 1} cooling area Length T carrier frequency q coolant flow Q amount of coolant

Claims (19)

For cooling the strand piece (4) of the metal strand in the cooling region (6) of the continuous casting machine by the cooling device (2) having a plurality of switching valves (8) and a plurality of cooling nozzles (10), respectively. A method,
The strand pieces (4) are transported through the cooling zone (6) for cooling;
The switching valve (8) is actuated by a binary pulse width modulation control signal (38-46, 52), whereby the coolant flow (q) is alternately discharged or blocked through the cooling nozzle (10) In which the coolant (12) is intermittently applied to the strand pieces (4) of the cooling region (6) for cooling,
The binary pulse width modulation control signal (38-46, 52) includes at least one of the control signals (38-46, 52) and the control signal (38-46, 52). A method characterized in that it is determined to have a phase shift (φ, φ ₁ , φ ₂ , Δφ) relative to another control signal.   The phase shift (Δφ) of one of the control signals (38-46, 52) is used to minimize the volume flow variation of the coolant (12) using a numerical optimization process. The method of claim 1, wherein the method is determined.   Method according to claim 1 or 2, characterized in that at least two of the control signals (38-46, 52) are determined to have different carrier frequencies (T). The carrier frequency (T) of one of the control signals (38-46, 52) depends on the speed (v) of the strand piece (4) and / or the length (L, L _1), and / or, characterized in that said determined according to the spray profile of the cooling nozzle (10) (34) the method according to any one of claims 1 to 3.   5. A method according to any one of the preceding claims, characterized in that at least two of the control signals (38-46, 52) are determined to have different pulse width ratios ([kappa]). The pulse width ratio (κ) of one of the control signals (38-46, 52) indicates whether there is an abnormality or failure in the cooling device (2) , and which element of the cooling device 6. A method according to any one of claims 1 to 5, characterized in that it is determined according to whether it has an anomaly or is malfunctioning .   In order to cool the strand pieces (4) in the cooling region (6) in which at least two cooling nozzles (10) are arranged continuously in the conveying direction (32) of the strand pieces (4) The method according to claim 1, wherein the method is used. For detection of an error condition of the cooling device (2),
One of the pressure, acceleration, sound pressure, flow rate of the coolant (12) for determining whether there is an abnormality or failure in the cooling device and / or the location of the element that has or has an abnormality More than one state variable (p, 26) is detected in the region of the coolant supply conduit (14) common to at least the plurality of switching valves (8) and / or the plurality of cooling nozzles (10). ,
The transition (58, 60, 64, 66) of the state variable (p, 26) is compared with the reference transition (62); and
An error condition of at least one of the switching valves (8) of the cooling device (2) and / or of at least one of the cooling nozzles (10) is detected on the basis of the comparison, The method according to any one of claims 1 to 7.   Using the transition of the state variable (p, 26), the frequency spectrum (58, 60, 64) of the state variable (p, 26) is detected and compared with a reference frequency spectrum (62). The method according to claim 8.   During detection of the state variable (p, 26), at least one of the switching valves (8) is activated by a control signal (38-46, 52) having a temporarily increased switching test frequency. 10. A method according to claim 8 or 9, characterized.   11. The state variable (p, 26) is detected by a pressure sensor (24) and / or a flow sensor and / or an acoustic sensor and / or an acceleration sensor. The method described in 1.   The method according to any one of the preceding claims, wherein the method is used in one cooling zone of the plurality of cooling zones (6) of the continuous casting machine.   12. A method according to any one of the preceding claims, used in each of a plurality of the cooling zones (6) of the continuous casting machine. In order to cool the metal strand piece (4) in the cooling zone (6) of the continuous casting machine, a cooling device (10) having a switching valve (8), a cooling nozzle (10), a coolant (12) and a control device (20). 2), the control device (20) determines a binary pulse width modulation control signal (38-46, 52), and the control signal (38-46, 52) controls the switching valve (8). In the cooling device (2) that is adjusted to operate,
The control device (20) is adjusted to determine a phase shift (φ, φ ₁ , φ ₂ , Δφ) of one of the control signals (38-46, 52). Features cooling device (2).   The control device (20) is adjusted to determine the carrier frequency (F) and / or pulse width ratio (κ) of one of the control signals (38-46, 52). The cooling device (2) according to claim 14, characterized in that: Whether there is an abnormality or failure in the cooling device in the region of the coolant supply conduit (14) common to at least a plurality of said switching valves (8) and / or at least a plurality of said cooling nozzles (10) and / or Detecting a state variable (p, 26) comprising one or more of the pressure, acceleration, sound pressure, flow rate of the coolant (12) for determining the position of an abnormal or faulty element. A measuring device (16) having a sensor (24) tuned to, and
-The transition (58, 60, 64, 66) of the state variable (p, 26) is compared with the reference transition (62) and adjusted to detect the error condition of the cooling device (2) based on the comparison 16. The cooling device (2) according to claim 14 or 15, characterized in that the detection device (18) is provided.   The detection device (18) detects the frequency spectrum (58, 60, 64) of the state variable (p, 26), and the frequency spectrum (58, 60, 64) of the state variable (p, 26). 17. The adjustment according to claim 16, characterized in that it is adjusted to detect a faulty switching valve (8) and / or cooling nozzle (10) using the comparison as compared to a reference frequency spectrum (62). Cooling device (2). The control device (20) shifts the phase of one control signal of the control signals (38-46, 52) in one cooling region of the plurality of cooling regions (6) of the continuous casting machine. 18. Cooling device (2) according to any one of claims 14 to 17, characterized in that it is adjusted to determine ([phi], [phi] ₁ , [phi] ₂ , [Delta] [phi]). The control device (20) controls the phase shift (φ, φ ₁ ) of one of the control signals (38-46, 52) in each of the plurality of cooling regions (6) of the continuous casting machine. , Φ ₂ , Δφ) are adjusted to determine the cooling device (2) according to claim 14.