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    • 专利摘要:
    The invention relates to a method for cooling a strand section (4) of a metallic strand in a cooling region (6) of a continuous casting machine with a cooling device (2), comprising switching valves (8) and cooling nozzles (10), wherein the strand section (4) for cooling is conveyed through the cooling region (6) and the switching valves (8) are controlled by binary pulse width modulated control signals (38-46, 52), whereby coolant flows (q) are alternately released or interrupted by the cooling nozzles (10), whereby a coolant (12 ) is applied for cooling intermittently on the strand section (4) in the cooling region (6), and a method for determining a fault condition of the cooling device and a cooling device. Uniform application of coolant can be achieved if the binary pulse-width-modulated control signals (38-46, 52) are determined in such a way that the strand section (4) conveyed through the cooling region (6) at the end (36) of the cooling region (6) has a substantially over the strand section (4) has been acted upon same Kühlmittelbeaufschlagungsdichte.
    公开号:AT516075A1
    申请号:T50523/2014
    申请日:2014-07-25
    公开日:2016-02-15
    发明作者:Thomas Dipl Ing Fuernhammer；Peter Dipl Ing Ladner；Markus Dipl Ing Mairhofer；Rudolf Scheidl；Rene Dipl Ing Stellnberger；Helmut Dipl Ing Wahl；Philipp Dipl Ing Wieser；Stefan Dipl Ing Woess
    申请人:Primetals Technologies Austria GmbH；
    IPC主号:
    专利说明:

    Cooling of a metallic strand section
    The invention relates to a method for cooling a strand section of a metallic strand according to the preamble of claim 1, a method for determining a defect state of a cooling device according to the preamble of claim 10, and a cooling device according to the preamble of claim 14.
    In the continuous casting of metals, a metallic melt is fed to a usually oscillating, water-cooled mold, solidified therein at least in the edge zone and usually continuously - already in the form of a strand - fed from the mold of the mold downstream strand guiding device of the continuous casting machine and conveyed therethrough ,
    In this case, it is necessary to further cool the strand in the strand guiding device with a cooling device, usually by applying a coolant to the strand.
    From WO 2012/163878 a method for cooling a metallic strand is known in which a coolant from a plurality of along a conveying direction of the strand arranged cooling nozzles is applied to the strand. For cooling the strand according to the method, WO 2012/163878 proposes a cooling device with switching valves and cooling nozzles.
    It is an object of the present invention to achieve a reliable and efficient cooling of a strand section of a metallic strand.
    This object is achieved by a method having the features of claim 1, a method having the features of claim 10 and a cooling device having the features of claim 14.
    Advantageous embodiments and advantages of the invention will become apparent from the further claims and the description and refer to the method and the cooling device.
    The inventive method for cooling a strand section of a metallic strand in a cooling area of a continuous casting machine with a cooling device, comprising switching valves and cooling nozzles, in which the strand section for cooling through the cooling area is promoted and the switching valves are controlled by binary pulse width modulated control signals, whereby coolant flows through the cooling nozzles are alternately released or interrupted, whereby a coolant for cooling is intermittently applied to the strand section in the cooling area provides that the binary pulse width modulated control signals are set such that the conveyed through the cooling area strand section at the end of the cooling area with a substantially over the strand section has the same Kühlmittelbeaufschlagungsdichte acted upon.
    The invention is based on the recognition that in the promotion of the strand through the cooling region primarily along the strand a differently strong re-heating of the strand surface - due to heat conduction from the strand interior - adjusts. It is therefore desirable to be able to change the cooling capacity along the strand or the cooling device. Otherwise, it can lead to a loss of metallurgical quality or overcooling of the strand. For this purpose, it is on the one hand advantageous to apply the coolant intermittently - ie with time interruptions - on the strand. In this way, a coolant amount and thus the cooling power can be adjusted in a simple, robust and energy-efficient manner over a wide range of values. On the other hand, in the intermittent coolant application - which is unsteady - a uniform coolant application can not be readily ensured, since it can lead to an unwanted interaction between the temporal interruptions of the cooling medium application and other process variables of the continuous casting process. If, for example, a strand section is partially or completely conveyed through a cooling area during a time interruption of the coolant application or, for example, also in the case of a defect in a cooling nozzle or the like, the strand section experiences an unwanted reduction in cooling or no cooling at all. This, in turn, may be accompanied by an undesirable reduction in strand quality. Such an unwanted reduction of the cooling or a loss of quality can be avoided if a uniform Kühlmittelbeaufschlagungsdichte - in terms of coolant quantity per unit area - is effected on the strand section. Essential here is the knowledge that the uniform Kühlmittelbeaufschlagungsdichte at the latest until the time of promotion of the strand section through the cooling area -also at the end of the cooling area - is effected. By the invention, the control signals are set in such a way - in simple terms, the time interruptions of the coolant application are adapted to the strand so targeted - that said disadvantage of the intermittent coolant application is overcome.
    A strand section may be a section of the strand in a strand longitudinal direction or in a conveying direction of the strand through the cooling region. In particular, a strand in its overall length may at least predominantly be formed from a plurality of strand sections. The division of the strand into a plurality of strand sections may be an imaginary division of a quasi-continuous - i. being integrally contiguous by at least half the length of the strand guiding device extending strand.
    The metallic strand can at least predominantly contain steel or be a steel strand.
    A cooling area in the sense of the present invention can be
    Be range through which the strand section or strand for the application of coolant is promoted. The cooling region is expediently arranged along the strand guiding device of the continuous casting machine, preferably within the region of the strand guiding device. The continuous casting machine can comprise a plurality of cooling regions arranged one behind the other, in particular in the conveying direction of the strand. For example, the cooling area may be an area wettable by coolant discharged from the cooling nozzle.
    The intermittent coolant application can be achieved by repeatedly switching back and forth between an open and a closed state of the switching valves. Conveniently, the switching valves are connected upstream of the cooling nozzles in the direction of coolant flow.
    Appropriately, the switching valves are driven by binary control signals. Binary can mean that the control signal can assume two states, in particular 0 or 1 or HI or LOW.
    Advantageously, in each case a switching valve is controlled by a control signal. However, it is also conceivable that a group of several switching valves is controlled by one and the same control signal, in particular simultaneously.
    A switching valve may in turn release or shut off a flow of coolant through a single cooling nozzle. It is also conceivable that several coolant flows are released or shut off by a group of several cooling nozzles through one and the same switching valve.
    Advantageously, the binary control signal is a pulse-width-modulated control signal whose signal properties can be defined by a carrier frequency, a pulse width ratio and a phase shift or the like.
    Definition in the sense of the present invention may mean that at least one signaling property of a control signal, for example the carrier frequency, is modulated or adapted or changed. The determination is advantageously carried out as a function of at least one state variable, which may be a state variable of the continuous casting process, the strand, the cooling device or the like.
    For the purposes of the present invention, the coolant admission density can be understood to mean a unit of quantity of the coolant in relation to a unit area of the strand section. Conveniently, coolant loading density is a quantity of coolant per unit area, which can be given for example with the unit of measure 1 / m 2.
    In simple terms, the invention contemplates that the intermittent intermittent application of coolant to the strand section in the cooling zone be controlled by modulation - i. a change in the signal properties of the control signals is adjusted such that a surface to be cooled of the strand section has undergone the same cooling performance by the action of the coolant after passing through the cooling region at each point.
    In order to determine the time interruption, it is advantageous to use the control signals - i. their properties - set using a conveying speed of the strand and / or a fault condition of the cooling device and / or a geometric property of the cooling region and / or a distance between two cooling nozzles or two rows of cooling nozzles or the like.
    In this way, a uniform coolant loading of the strand and thus a uniform metallurgical strand quality, in particular while maintaining the known advantages of the intermittent coolant application can be achieved.
    The method according to the invention for determining a fault condition of a cooling device, comprising switching valves actuated by control signals for enabling and interrupting coolant flows and cooling nozzles intermittently discharging coolant, a continuous casting machine in which a state variable describing the physical state of the coolant is determined, provides that the state variable is determined in the range of at least one of the switching valves and / or more of the cooling nozzles common coolant supply, a curve of the state variable is compared with a reference curve and depending on the comparison, a fault condition of at least one of the switching valves and / or one of the cooling nozzles of the cooling device is determined.
    The invention is based on the recognition that the cooling device for the application of the coolant can be impaired in its function at least partially due to the error.
    In order to be able to counteract an unwanted effect of such an error state on the uniform coolant admission of the strand section, it is desirable to specify a method with which a fault state of the cooling device can be reliably detected. A fault condition of the cooling device may be due to a defect of one or more of the switching valves and / or one or more of the cooling nozzles. For example, a switching valve and / or a plurality of switching valves due to blocking can no longer be switched from an open to a closed state and / or vice versa - i. blocked -in. Further, a switching valve and / or a cooling nozzle may be at least partially clogged or the like. In addition, a plurality of switching valves and / or a plurality of cooling nozzles may each be at least partially blocked or the like. It is essential to realize that a defective switching valve and / or a defective cooling nozzle must be clearly located in order to adjust the definition of the control signals according to the method, so that even in the presence of such a fault condition a uniform Kühlmittelbeaufschlagungsdichte can be achieved. In this case, the determination of a fault condition by one sensor per switching valve and / or per cooling nozzle can be complex and error-prone, since a large number of sensors is required. The invention makes it possible to reduce the metrological outlay for determining an error state by determining a state variable describing the state of the coolant in the region of at least one of the switching valves and / or several coolant supply lines common to the cooling nozzles. That In simple terms, a sensor is placed on the cooling device and a measured value is determined, instead of placing a plurality of sensors at several points of the cooling device in order to determine a plurality of measured values.
    Furthermore, the method allows the error state to be compensated for at least temporarily by appropriate definition of the control signals, without there being any unwanted effect on the strand quality. In this way, a replacement of a defective switching valve and / or a defective cooling nozzle delayed in time and a production-free life of the continuous casting machine can be reduced.
    The state variable may in particular be a state variable of the coolant, for example a pressure, an acceleration, a sound pressure, a flow or the like.
    Appropriately, the state variable is determined on a coolant supply line, which supplies a plurality of switching valves and / or cooling nozzles with coolant.
    The state quantity may be in a regular operation of the cooling device - i. during a strand production - and / or determined during a maintenance operation of the cooling device.
    The reference curve may be a course of the determined state variable over time, over a frequency or the like, which is or was determined in a fault-free operation of the cooling device.
    The comparison can be made by a mathematical operation taking into account the reference curve and the course of the state variable. The comparison can be made by a difference between the course of the state variable and the reference curve.
    The cooling device according to the invention, comprising switching valves, cooling nozzles and a coolant, for cooling a metallic strand section in a cooling region of a continuous casting machine, provides a measuring device, a determination device and a control device.
    The measuring device has a sensor which is prepared for determining a state variable describing the state of the coolant in the region of a coolant supply line common to at least a plurality of switching valves and / or cooling nozzles.
    The determination device is prepared for comparing a profile of the state variable with a reference profile and for determining an error state of the cooling device as a function of the comparison.
    The control device is prepared for the definition of binary pulse width modulated control signals and for driving the switching valves with the control signals.
    The invention is based on the recognition that for reliable and efficient cooling of the strand section measuring and control engineering measures are required. The invention makes it possible to implement these measures in accordance with the method in that the cooling device has the measuring device, the detection device and the control device thus configured.
    Preferred developments of the invention will become apparent from the dependent claims. The further developments relate both to the method according to the invention and to the cooling device according to the invention.
    The invention and the developments described can be implemented both in software and in hardware, for example using a special electrical circuit.
    Furthermore, a realization of the invention or a further development described is possible by a computer-readable storage medium on which a computer program is stored, which carries out the invention or the development.
    The invention and / or any further development described can also be realized by a computer program product which has a storage medium on which a computer program is stored which carries out the invention and / or the development.
    The coolant loading density can be influenced inadvertently, in particular, by undesired fluctuations in a coolant flow rate in lines or supply lines of the cooling device. Such variations may be caused by pressure surges in the coolant, which in turn may be caused by the intermittent circuit - i. the opening and closing of the switching valves can be caused. The height of the pressure surges and thus the height of the fluctuations can be reduced by an advantageous determination of the control signals.
    In particular, therefore, in an advantageous embodiment, at least one of the control signals is set with a phase shift to another of the control signals.
    Due to the phase shift, a time-shifted switching of the driven by the phase-shifted control signals
    Switching valves are effected. The time offset can cause a reduction of the pressure surges and thus a homogenization of the coolant flow rate. Such can be counteracted by simple means of an unwanted influence on the Kühlmittelbeaufschlagungsdichte.
    Starting from a control of a number of n switching valves, each with a control signal - each having the same characteristics, such as a carrier frequency F and a pulse width ratio K- a phase shift φ via a simple calculation approach, for example, φ = tp / n be set, where tp the period of the control signal, that is, the reciprocal of the carrier frequency F is.
    In particular, if the control signals have different carrier frequencies and / or pulse width ratios, it may be necessary to deviate from simple arithmetic calculation approaches for determining the control signals.
    In a further refinement, a phase shift of one of the control signals is determined using a numerical optimization method for minimizing a volume flow fluctuation of the coolant.
    The volume flow fluctuation can describe a fluctuation of a coolant flow through a line or feed line of the cooling device. For the optimization procedure, a frequency spectrum of the volume flow can be determined. The frequency spectrum can be split into a constant and a trigonometric term. The trigonometric term may depend on the pulse width ratios and the phase shifts of the switching signals. Given the pulse width ratios of the control signals, the optimization may involve the adaptation of the phase shifts.
    The optimization method can be carried out with a so-called genetic algorithm, a gradient-based method or the like.
    According to a preferred development, at least two of the control signals are set with different carrier frequencies.
    A carrier frequency may be the reciprocal of a time period between two state changes of a control signal from LOW to HI and / or from HI to LOW, respectively. A comparatively high carrier frequency can cause a comparatively fast intermittent coolant application. In other words, the carrier frequency may be the reciprocal of a period of a control signal cycle.
    The at least two control signals can each control a switching valve, the respective switching valve in each case release and / or interrupt a coolant flow through a cooling nozzle. In this way, different amounts of coolant can be applied to the strand by the cooling nozzles addressed in this way. The application of different quantities of coolant in such a manner-in particular in different regions of the cooling device, preferably in the conveying direction of the strand-can be advantageous for achieving the same coolant loading density over the strand section.
    If there is an unfavorable interaction between the carrier frequency-and thus between the time interruption of the coolant application-and a process-related size of the continuous casting process and / or a parameter of the continuous casting machine, the coolant admission density may be undesiredly influenced.
    In particular, therefore, in an advantageous development, a carrier frequency of one of the control signals is determined as a function of a speed of the strand section.
    In this way, a uniform Kühlmittelbeaufschlagungsdichte can be achieved even with a change in the strand or casting speed.
    Moreover, it is advantageous if a carrier frequency of one of the control signals is determined as a function of a length of the cooling region.
    The length of the cooling region may be an extension of the cooling region substantially along the strand conveying direction.
    The length of the cooling region may be a length of a region to be acted upon by a cooling nozzle with coolant.
    Since it is possible that the cooling device comprises cooling regions with different lengths, a uniform coolant loading density can be achieved in this way, in particular under such circumstances.
    Furthermore, it is advantageous if a carrier frequency of one of the control signals is determined as a function of a passage time of the strand by a region which can be acted upon by a cooling nozzle with coolant, in particular a cooling region.
    The cycle time can be the quotient of the length of the cooling zone and the strand velocity.
    Furthermore, it is advantageous if a carrier frequency of one of the control signals is determined as a function of a spray profile of the cooling nozzles.
    The spray profile may be a curve of an achievable coolant loading density along a surface wetted by a cooling nozzle.
    A rectangular spray profile is conceivable in which each wetted point along the surface is exposed to the same amount of coolant.
    In particular, in the presence of a rectangular spray profile, it is advantageous if the reciprocal of the carrier frequency F, i. the period duration tp of a control signal is determined according to the equation tp = xn / (k * v), where xn is the length of the cooling region, k is a positive integer value (1, 2, 3, ...) and v is the velocity of the strand is.
    Further conceivable is a triangular spray profile in which the Kühlmittelbeaufschlagungsdichte increases along the applied surface of a minimum linearly to a maximum and thereafter again linearly decreases to the minimum.
    In particular, in the presence of a triangular spray profile, it is advantageous if the reciprocal of the carrier frequency F, i. the period duration tp of a control signal is determined according to the equation tp = xn / (g * v), where xn is the length of the cooling zone, g is a positive even number (2, 4, 6, ...) and v is the velocity of the strand is.
    It is advantageous if the phase shift of one of the control signals is determined as a function of a speed of the strand and / or a length of the cooling region and / or a spray profile of the cooling nozzles.
    By determining one or more of the control signals in the aforementioned manner, it can be achieved that the admission of a strand section with coolant after passing through a cooling region has essentially the same coolant application density over the strand section.
    In an advantageous embodiment, at least two of the control signals are set with different pulse width ratios.
    The pulse width ratio may be the relative proportion of a control signal pulse - i. a binary HI state - describe the period of the control waveform. For example, a pulse width ratio of 100% describes a control signal with a permanent state 1 or HI. For example, a pulse width ratio of 50% describes a control signal having a rectangular profile whose rectangular pulses each last half of a period duration.
    To compensate for a quantity of coolant that has not been applied by mistake-for example as a result of a defective cooling nozzle-it is advantageous if an increased amount of coolant is applied to the strand through a further cooling nozzle.
    In particular, therefore, it is advantageous if a pulse width ratio of one of the control signals is determined as a function of a fault condition of the cooling device.
    If, for example, an error condition occurs in the form of a defective cooling nozzle, the pulse width ratio of a control signal for actuating a further cooling nozzle is changed such that the quantity of coolant that is not applied due to the defect is additionally applied to the strand by means of the further cooling nozzle. In this way, it is possible to counteract unwanted, erroneously uneven coolant admission of the strand.
    Advantageously, the fault condition of the cooling device is determined by a method according to at least one of claims 11 to 14.
    If the coolant is applied to the strand within a cooling region by means of only one cooling nozzle or one cooling nozzle row, a uniform coolant application density can not be readily achieved, in particular with a particularly high casting speed or a particularly short length of a cooling region.
    In an advantageous development, the method is used for cooling a strand section in a cooling region, in which at least two of the cooling nozzles are arranged one behind the other in a conveying direction of the strand section. In this way, a coolant amount compensation over more than one cooling nozzle (nreihe) done with simple means.
    According to a preferred embodiment, a frequency spectrum of the state variable is determined using a course of the state variable and compared with a reference frequency spectrum.
    The course of the state variable can be a time course, in particular a course of a pressure over time. The determination of the frequency spectrum can be carried out with a so-called fast Fourier transformation method or the like. The reference frequency spectrum is a frequency spectrum that is or was determined with a faultless function of the cooling device.
    By driving and switching a switching valve for intermittent coolant application, a state variable impact - ie an abrupt change of a state variable over time - of the coolant in the coolant supply line can be effected. Such a burst may be a frequency spectrum with a frequency peaking - i. a peak or the like - show up. In this case, the switching of a plurality of switching valves can effect a plurality of respectively characteristic frequency peaks within the frequency spectrum, wherein individual peaks can be assigned to individual switching valves and / or cooling nozzles. By means of the comparison with the reference spectrum, a defective switching valve and / or a defective cooling nozzle can be determined and located in a simple manner in this way.
    In addition, it is advantageous if at least one of the switching valves during the determination of the state variable by a
    Control signal is driven with a temporarily increased switching test frequency.
    Appropriately, a frequency spectrum of the state variable is determined. If the switching test frequency is not included as a characteristic frequency increase in the frequency spectrum, it is possible to conclude an error condition at the switching valve controlled by the switching test frequency and / or a cooling nozzle downstream of this switching valve.
    Advantageously, a plurality of switching valves, which are fed from a common coolant supply line, one after the other, preferably for 2 s to 4 s, driven with the switching test frequency. It is advantageous if the switching test frequency exceeds a usual switching frequency or carrier frequency of the switching valves by at least a factor of two. In this way, a fault condition during a regular operation of the cooling device can be determined while avoiding an influence on the Kühlmittelbeaufschlagungsdichte.
    According to a preferred embodiment, the state variable is determined with a pressure sensor. Pressure sensors are widely tried and available in a variety of adapted to the particular application embodiments. In this way, the state variable can be determined reliably and inexpensively.
    In an advantageous embodiment, the state variable is determined with a flow sensor. In many cases, a flow meter for determining a coolant consumption anyway part of the cooling device, so that the state variable can be determined particularly cost.
    In a further advantageous embodiment, the state variable is determined with a sound sensor. In this case, the sound can be determined, for example, directly to a coolant supply line or indirectly at another location of the Kühlein direction and an introduction of a sensor in the coolant flow can be avoided. Such a spatially particularly flexible determination of the state variable can be achieved.
    Advantageously, the state variable is determined with an acceleration sensor. Acceleration sensors are widely tried and available in a variety of adapted to the particular application embodiments. In this way, the state variable can be determined reliably and inexpensively.
    According to a preferred embodiment, the determination device is prepared for determining a frequency spectrum of the state variable, preferably using a time characteristic of the state variable.
    Moreover, it is advantageous if the determination device is prepared for comparing the frequency spectrum of the state variable with a reference frequency spectrum.
    Furthermore, it is advantageous if the determining device is prepared for determining defective switching valves and / or cooling nozzles using the comparison.
    In an advantageous development, the control device is prepared for determining a phase shift of one of the control signals.
    Moreover, it is advantageous if the control device is prepared for determining a carrier frequency of one of the control signals.
    Furthermore, it is advantageous if the control device is prepared for establishing a pulse width ratio of one of the control signals.
    The previously given description of advantageous embodiments contains numerous features that are given in the individual sub-claims partially summarized in several. However, these features may conveniently be considered individually and summarized to meaningful further combinations. In particular, these features can be combined individually and in any suitable combination with the method according to the invention and the arrangement according to the invention according to the independent claims.
    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 in connection with the following description of embodiments, which will be described in connection with the drawings. The embodiments serve to illustrate the invention and do not limit the invention to the combination of features specified therein, not even with respect to functional features. In addition, suitable features of each embodiment may also be explicitly considered isolated, removed from one embodiment, incorporated into another embodiment to complement it, and / or combined with any of the claims.
    1 shows a schematic representation of a cooling device having switching valves and cooling nozzles for cooling a metallic strand section, FIG. 2 shows a schematic representation of binary pulse width modulated control signals for controlling the switching valves of FIG. 1, FIG. 3 shows a diagram for clarifying a relationship between coolant admission density 4 shows a diagram analogous to FIG. 3 in the case of a triangular spray profile of the cooling nozzles in the conveying direction of a strand section, FIG. 5 shows a diagram of a frequency spectrum of the coolant pressure during switching of a switching valve of the switching valves of FIG 5 shows a diagram of a frequency spectrum according to FIG. 5 when switching a plurality of switching valves, FIG. 7 shows a diagram with a comparison of two frequency response curves.
    Curves in the presence of a fault condition on one of the switching valves and / or cooling nozzles of FIG 1, 8 is a diagram of a pressure curve over time at
    9 shows schematic representations of an optimization method for minimizing a volumetric flow fluctuation of the coolant in the coolant supply line of FIG. 1. FIG. 1 shows a schematic representation of a cooling device 2 for cooling a metallic strand section 4 in one Cooling area 6 of a continuous casting machine. The latter is not shown for reasons of clarity.
    The cooling device 2 has switching valves 8, cooling nozzles 10, a coolant supply line 14 leading to a coolant 12, a measuring device 16, a determination device 18 and a control device 20. In the present embodiment, in each case one of the switching valves 8 is connected upstream of one of the cooling nozzles 10. It is of course also conceivable that a plurality of cooling nozzles, for example a so-called cooling nozzle bar, are addressed by a single switching valve.
    The cooling region 6 has the length L and comprises six cooling nozzles 10 arranged one behind the other. However, it is also possible that a cooling region comprises only one of the cooling nozzles 10 and has a length Li.
    The measuring device 16 has a sensor 24 which is arranged on the coolant supply line 14 or a measuring point 22 and which is prepared for determining a profile of a state variable describing the state of the coolant 12. In the present exemplary embodiment, this state variable is the pressure 26 of the coolant 12 at the measuring point 22.
    The determination device 18 is prepared for comparing a course of the pressure 26 - a time and / or a frequency curve or the like - with a reference curve and for determining a fault condition of the cooling device 2 as a function of the comparison.
    The control device 20 is prepared for establishing binary pulse width modulated control signals (see FIG. 2: 38, 40, 42, 44) and for controlling the switching valves 8 with the control signals via signal lines 28. During a continuous casting process, the strand section 4 is guided between strand guide rollers 30 and for cooling in a conveying direction 32 - also casting direction - at a speed v by the length L - is conceivable also the length Li - extending cooling region 6 promoted, i. moved past the cooling nozzles 10.
    Here, the switching valves 8 are each controlled by the control device 20 with a binary pulse width modulated control signal, whereby coolant flows are alternately released or interrupted by the cooling nozzles 10, whereby the coolant 12 applied intermittently for cooling on the strand section 4 in the cooling region 6 becomes. The cooling nozzles 10 each have a triangular spray profile 34 in the conveying direction 32.
    The binary pulse-width-modulated control signals are determined by the control unit 20 such that the strand section 4 conveyed through the cooling region 6 has been acted on at the end 36 of the cooling region 6 by a coolant impingement density which is substantially the same across the strand section 4.
    In particular, it can also be seen from the illustration that, according to the state of the art, uniform application of coolant to the strand section 4 as a result of the intermittent application of the coolant is not readily possible.
    In an unfavorable determination of the control signals, there may be occurrences that - depending on the speed v, length L or Li, a failure of one of the switching valves 8 and / or one of the cooling nozzles 10 or the like - parts of the strand section 4 during a time interruption of the coolant application under a cooling nozzle 10 are conveyed through, without being subjected to coolant 12. As a result, according to the prior art, an unwanted coolant impingement density over the strand section 4 at the end 36 of the cooling section 6 may be caused.
    The method is not limited in its use to the cooling arrangement shown in this embodiment, in particular for cooling a strand section in the form of a long product in particular, in the form of a so-called Beam Blanks, Blooms, Billets, Rounds - also: carrier, billet or billet - or the like is suitable. Other cooling arrangements, for example for cooling slabs - also: slabs - can also be operated according to the cooling method. FIG 2 shows a schematic representation of exemplary courses of binary pulse width modulated control signals 38, 40, 42 and 44 over the time t for driving the switching valves 8 of FIG 1. The illustration illustrates the adaptability to the determination of the control signals or modulated egg, namely Period duration, pulse width ratio and time offset.
    From FIG. 2 it can be seen that the control signals 38 to 44 change in their ordinate-applied signal state u over the time t between 1 and HI and a 0 or LOW, ie are binary in the sense of signal technology.
    The control signal 38 is fixed with a period duration tp and a pulse width ratio κ = ti / tp, where ti is a pulse duration. The reciprocal of the period l / tp is the carrier frequency F of the control signal 38.
    In this case, the higher the carrier frequency F, the shorter is a switching cycle between an open and a closed state of the switching valves 8 controlled in this way and the shorter are the time interruptions of the coolant application to the strand section 4 by the cooling nozzles 10 connected downstream of this switching valve. or downstream cooling nozzles 10th
    The control signal 40 is set in comparison to the control signal 38 with a doubled period 2 * tp, thus has a carrier frequency F / 2. Although the absolute pulse width of the control signals 38 and 40 is equal, the pulse width ratio of the control signal 40 is k / 2. As a result, in a control of a switching valve with the control signal 40 compared to the control with the control signal 38 within a switching cycle, only half of a coolant quantity is applied.
    The control signal 42 has the same period 2 * tp compared to the control signal 40. In this case, the absolute pulse width is ti / 2, so that the pulse width ratio of the control signal is 42 k / 4 = (ti / 2) / (2 * tp).
    The control signal 44 is set in comparison with the control signals 38, 40 and 42 with a time delay tz and thus has a phase shift φ. 3 shows a diagram for clarifying a relationship between the Kühlmittelbeaufschlagungsdichte and the determination of the control signals based on the signal properties illustrated by FIG 2. In particular, FIG. 3 shows a state (ordinate, u) of a control signal 46 over time (abscissa, t). The control signal 46 is fixed with a pulse duration ti and a period tp = 2 * ti, thus has a pulse width ratio of K = 50%.
    The curvature of the control signal 46 corresponds to an average coolant flow q - i. an average amount of coolant per unit time - which is discharged by a indirectly actuated with the control signal 46 cooling nozzle in a cooling area. Further, the area enclosed by the curve 46 up to a time t corresponds to an amount of refrigerant discharged up to this time.
    A partial section of a strand section enters the cooling area at time tio and emerges therefrom at time t2o and in the interim is supplied with a coolant quantity Q. In this case, the quantity of coolant Q applied to the subsection corresponds to the shaded area enclosed by a dashed line region 48 under the curve 46.
    Occurs another portion of the strand portion - illustrated by an area 50 - at time t30 in the cooling area and at time t40 from this, he is charged with the same amount of coolant Q.
    Both subsection of the strand section pass through the cooling area in a same cycle time tn - thus have the same length or area assuming the same speed v - and are subjected to the same amount of coolant Q. Accordingly, the strand section, which is conveyed through the cooling region and formed by the two regions 48 and 50, has a uniform coolant loading density at the end of the cooling region.
    The respective cycle time tn of the regions 48 and 50 through the cooling region acted upon by the mean coolant flow q is twice the period tp.
    In this case, the cycle time tn is determined by the length of the cooling region Li and the strand velocity v.
    If you move mentally one of the dashed lines 48, 50 along the time axis t, which is equivalent to a promotion of the strand section through the cooling area, the same hatched area is always included and thus achieved a uniform Kühlmittelbeaufschlagungsdichte.
    This is achieved because the period duration tp of the control signal 46 is determined as a function of the speed v of the strand section 4 and / or the length of the cooling region Li and / or the spray profile 34 of the cooling nozzles 10. FIG. 4 shows, in analogy to FIG. 3, the relationships in the case of a triangular spray profile of the cooling nozzles in the conveying direction of a strand section. The following description is essentially limited to the differences from the exemplary embodiment in FIG. 3, to which reference is made with regard to features and functions that remain the same. Substantially identical components are basically numbered with the same reference numerals, and features not mentioned are adopted in the following exemplary embodiments without being described again.
    In particular, FIG. 4 shows a control signal course 52 and two areas 54 and 56 of a strand section. The regions 54, 56 of the strand section enter the cooling region at times t50 and teo, respectively, and are discharged from the cooling region at times t70 and t8o, respectively, and are supplied with the same amount of coolant Q. Accordingly, the strand section, which is conveyed through the cooling region and formed by the two regions 54, 56, has a uniform coolant loading density at the end of the cooling region. Decisive for this is that the period tp is an even multiple of the cycle time tn. FIG. 5 shows a diagram of a frequency spectrum of the pressure (ordinate: p (bar), abscissa: f (Hz)) of the coolant 12 in the supply line 14 of the cooling device 2 from FIG. 1 when one of the switching valves 10 is actuated. 26, see FIG 1) can be determined with the sensor 24 of the measuring device 16. The frequency spectrum is determined by the determination device 18 (see FIG. 1) from a time curve of the pressure, here by means of a so-called FFT analysis (fast Fourier transformation). It is also possible to perform a so-called partial FFT analysis, i. a fast Fourier transform for a specific frequency range.
    The frequency spectrum has a resonance peak 58 at a frequency f of about 75 Hz. The resonant peak 58 is due to a surge in the coolant supply line 14, which is caused by the switching of one of the switching valves 10. 6 shows a diagram of a frequency spectrum of the coolant pressure (ordinate: p (bar), left abscissa: f (Hz)) upon actuation of several of the switching valves 10 (right-hand abscissa: valve number n (-)). The coolant pressure p is again determined at the measuring point 22.
    The frequency spectrum has a resonance peak 60 at a frequency f of about 75 Hz. In this case, the amplitude of the resonant peak 60 rises above the valve number n.
    This increase can be explained by a present in the present embodiment, greater distance with increasing valve number n to the measuring point, whereby a hydraulic inductance increases and higher pressure peaks in the coolant 12 are induced.
    To determine a fault condition at the cooling device 2, in particular at the switching valves 8 and / or the cooling nozzles 10, the frequency spectrum - in particular the course of the resonant peak 60 - is compared by the detection device 18 with a reference curve.
    From the deviation between the reference curve and the course of the resonance peaking determined by means of the comparison, it is possible, for example, to deduce a degree of clogging of one or more of the switching valves 8 and / or cooling nozzles 10.
    The advantage of this approach lies in the continuous and thus online - ie during a regular continuous casting process - possible fault detection. 7 shows a diagram with a comparison of two frequency curves 62 and 64 of the coolant pressure p (ordinate: p (bar), abscissa: f (Hz)) in the presence of an error state on one of the switching valves 8 and / or cooling nozzles 10 of FIG The curves 62 and 64 refer to the activation of a single one of the switching valves 10.
    The frequency profile 62 indicates a fault-free state, ie represents a reference frequency characteristic. The frequency characteristic 64 is established, for example, in the case of a clogged, non-switchable or otherwise non-switchable switching valve and / or an impaired cooling nozzle. The comparison between the two frequency curves 62 and 64 can clearly determine a fault condition. 8 shows a diagram with a pressure curve 66 over time (abscissa: t (s)) upon actuation of the switching valves 8 from FIG. 1 with a switching test cycle 68, which is determined by the time profile of the control signals. The determination of an error state can in turn be done by a comparison with a reference curve or alternatively by an adjustment of the pressure peaks 70 with each other.
    It is possible to fold the pressure profile 66, or a signal describing the pressure profile 66, with a suitable convolution signal. The convolution signal can be chosen such that amplification and / or noise suppression are as advantageous as possible. For example, a function sin2 (t) can be selected as the convolution signal or function. Furthermore, it is possible to consider the switching valve behavior and the resulting time derivatives.
    It is advantageous if the switching test cycle is determined with circuits distributed evenly over the switching test cycle duration.
    FIGS. 9 to 11 show a schematic illustration of an optimization method for minimizing a volumetric flow fluctuation of the coolant 12 in the coolant supply line 14 of FIG. 1. By minimizing the volumetric flow fluctuation, it is possible to counteract unwanted influencing of the coolant admission density.
    If the control signals for controlling the switching valves are determined with the same pulse width ratios, then a simple approach can be used:
    For example, a variable delay times tz (see FIG. 2) between the pulse sequences of the control signals, the repercussions on the higher-level supply system-that is, the volume flow fluctuation-can be minimized. For this simple approach to defining the control signals, a group of six switching valves is exemplified. 1, 8) with 6 downstream cooling nozzles 10, which are driven with a carrier frequency F of 1 Hz and the same pulse width ratio of κ 50%. With simultaneous switching of the switching valves undesirably high pressure surges in the common coolant supply line 14 are induced, which can lead to volume flow fluctuations and thus to an unwanted influence on the Kühlmittelbeaufschlagungsdichte.
    If the switching valves are actuated with a time delay, with e.g. 0.1 s each delay, so can reduce the unwanted system feedback.
    However, if the control signals for actuating the switching valves are defined with different pulse width ratios κ, this simple approach can no longer be used and it is advantageous to use the optimization method illustrated in FIGS. 9 to 11 for determining the control signals.
    For this purpose, a frequency spectrum of the flow or the volume flow of the coolant 12 is determined by the coolant supply line 14. The determination of this frequency spectrum can be carried out, for example, from the pressure p determined with the sensor 24 of the measuring device 16 for the indirect determination of the volume flow of the coolant 12 or by a direct determination of the volume flow and a subsequent FFT by means of the detection device 18.
    It is possible to determine the frequency spectrum by means of a simulation method, for example as part of a so-called pre-simulation. It is advantageous to use common simulation tools for this purpose.
    The frequency spectrum of the flow A is split into a constant and a trigonometric term, wherein the trigonometric term is dependent both on the pulse width ratio κ and the switching delay times tz. FIG. 9 shows the result of this decomposition in the case of a circuit of two switching valves in a notation in the complex number plane 72 (abscissa: real part Re, ordinate: imaginary part, Im). In this case, the amounts of the flows Ai and A2 depend on the respective pulse width ratio k of the control signal activating the respective switching valve. The phase shifts φι and φ2 are dependent on the respective delay time tz.
    The resulting pointer 74 with the total amount Av must be minimized in this case. 10 shows the result of the optimization for the exemplary case that ten switching valves are controlled by ten control signals with the same pulse width ratios κ.
    As a result, the optimization provides ten in the complex number plane by the same optimized phase shift 76 (Δφ) rotated flows Ai to Ai0. The optimization can be done with a genetic algorithm, a gradient-based optimization method or the like. A cost function is optimized which can be described by the sum of the squares of the squares of the complex vectors Av, summed over all Fourier terms considered. 11 shows an alternative graphical representation of the optimization result.
    List of Reference Numerals 2 cooling device 4 strand section 6 cooling zone 8 switching valves 10 cooling nozzles 12 coolant 14 coolant supply 16 measuring device 18 determining device 20 control device 22 measuring point 24 sensor 26 pressure 28 signal lines 30 strand guide rollers 32 conveying direction 34 spray profile 36 end cooling region 38, 40, 42, 44 control signal 46 control signal 48, 50 Range 52 Control signal 54, 56 Range 58, 60 Resonance peak 62 Reference frequency curve 64 Frequency curve 66 Pressure time curve 68 Switch test cycle 70 Pressure peaks 72 Complex number plane 74 Resulting pointer 76 Optimized phase shift t Time tio, t2o, t30, t40 Time tso, t60, t70, t80 Time tn Cycle time tp period ti pulse duration tz time delay u signal state K pulse width ratio φ, φι, φ2 phase shift Δφ optimized phase shift
    Ai to Aio coolant flow
    Av resulting coolant flow F Carrier frequency L, Li Length Cooling range T Carrier frequency q Coolant flow Q Coolant quantity
    权利要求:
    Claims (15)
    [1]
    1. A method for cooling a strand section (4) of a metallic strand in a cooling area (6) of a continuous casting machine with a cooling device (2), comprising switching valves (8) and cooling nozzles (10), wherein - the strand section (4) for cooling is driven by the cooling region (6) and - the switching valves (8) are controlled by binary pulse width modulated control signals (38-46, 52), whereby coolant flows (q) are alternately released or interrupted by the cooling nozzles (10), whereby a coolant ( 12) for cooling is intermittently applied to the strand section (4) in the cooling region (6), characterized in that - the binary pulse width modulated control signals (38-46, 52) are determined such that the through the cooling region (6) promoted strand section (4) at the end (36) of the cooling region (6) with a substantially over the strand section (4) gleichzuschicht equal Kühlmittelbeaufschlagungsdichte has been laid.
    [2]
    2. The method according to claim 1, characterized in that at least one of the control signals (38-46, 52) with a phase shift (φ, φι, φ2, Δφ) to another of the control signals (38-46, 52) is set.
    [3]
    3. The method according to claim 1 or 2, characterized in that a phase shift (Δφ) one of the control signals (38-46, 52) is determined using a numerical optimization method for minimizing a volume flow fluctuation of the coolant (12).
    [4]
    4. The method according to any one of the preceding claims, characterized in that at least two of the control signals (38-46, 52) are set with different carrier frequencies (T).
    [5]
    5. The method according to any one of the preceding claims, characterized in that a carrier frequency (T) of the control signals (38-46, 52) in dependence of a speed of the strand section (v) and / or a length of the cooling region (L, Li) and / or a spray profile (34) of the cooling nozzles (10) is set.
    [6]
    6. The method according to any one of the preceding claims, characterized in that at least two of the control signals (38-46, 52) are set with different pulse width ratios (k).
    [7]
    7. The method according to any one of the preceding claims, characterized in that a pulse width ratio (k) of one of the control signals (38-46, 52) in dependence on a fault condition of the cooling device (2) is set.
    [8]
    8. The method according to claim 7, characterized in that the error state of the cooling device (2) is determined by a method according to at least one of claims 10 to 13.
    [9]
    9. The method according to any one of the preceding claims, used for cooling a strand section (4) in a cooling region (6), in which at least two of the cooling nozzles (10) in a conveying direction (32) of the strand section (4) are arranged one behind the other.
    [10]
    10. A method for determining a fault condition of a cooling device (2), comprising switching valves (8) actuated by control signals (38-46, 52) for releasing and interrupting coolant flows (q) and the coolant (12) intermittently discharging cooling nozzles (10), a continuous casting machine, in which - a physical quantity of the coolant (12) descriptive state variable (p, 26) is determined, characterized in that - the state variable (p, 26) in the range of at least one of the switching valves (8) and / or a coolant line (14) common to the cooling nozzles (10) is determined, - a curve (58, 60, 64, 66) of the state variable is compared with a reference curve (62) and - depending on the comparison, a fault state of at least one of the switching valves (8 ) and / or one of the cooling nozzles (10) of the cooling device (2) is determined.
    [11]
    11. The method according to claim 10, characterized in that using a course of the state variable (p, 26) determines a frequency spectrum (58, 60, 64) of the state variable and compared with a reference frequency spectrum (62).
    [12]
    12. The method according to any one of claims 10 or 11, characterized in that during the determination of the state variable (p, 26) at least one of the switching valves (8) by a control signal (38-46, 52) is driven with a temporarily increased switching test frequency.
    [13]
    13. The method according to claim 10 to 12, characterized in that the state variable with a pressure sensor (24) and / or a flow sensor and / or a sound sensor and / or an acceleration sensor is determined.
    [14]
    14. Cooling device (2), comprising switching valves (8), cooling nozzles (10) and a coolant (12), for cooling a metallic strand section (4) in a cooling region (6) of a continuous casting machine, characterized by - a measuring device (16), comprising a sensor (24) which is prepared to determine a state of the coolant (12) descriptive state variable (p, 26) in the region of at least a plurality of switching valves (8) and / or cooling nozzles (10) common coolant supply line (14) a determination device (18) prepared for comparing a profile (58, 60, 64, 66) of the state variable (p, 26) with a reference curve (62) and for determining a fault state of the cooling device (2) as a function of the comparison, and a control device (20), prepared for the definition of binary pulse width modulated control signals (38-46, 52) and for driving the switching valves (8) with the control signals (38-46, 52).
    [15]
    15. Cooling device (2) according to claim 14, characterized in that - the determining device (18) for determining a frequency spectrum (58, 60, 64) of the state variable (p, 26), for comparing the frequency spectrum (58, 60, 64 ) of the state variable (6, 26) with a reference frequency spectrum (62) and for the determination of defective switching valves (8) and / or cooling nozzles (10) is prepared using the comparison, - the control means (20) for determining a phase shift (φ , φι, φ2, Δφ) and / or a carrier frequency (F) and / or a pulse width ratio (k) of one of the control signals (38-46, 52) is prepared.
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    同族专利:
    公开号 | 公开日
    EP3171998A1|2017-05-31|
    JP6400830B2|2018-10-03|
    WO2016012471A1|2016-01-28|
    KR20170036042A|2017-03-31|
    KR102312840B1|2021-10-14|
    EP3171998B1|2018-04-18|
    AT516075B1|2018-09-15|
    JP2017521262A|2017-08-03|
    ES2678774T3|2018-08-17|
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    法律状态:
    2021-03-15| MM01| Lapse because of not paying annual fees|Effective date: 20200725 |
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50523/2014A|AT516075B1|2014-07-25|2014-07-25|Cooling of a metallic strand section|ATA50523/2014A| AT516075B1|2014-07-25|2014-07-25|Cooling of a metallic strand section|
    JP2017504073A| JP6400830B2|2014-07-25|2015-07-22|Cooling of metal strand pieces|
    ES15744524.8T| ES2678774T3|2014-07-25|2015-07-22|Cooling of a metal bar segment|
    PCT/EP2015/066700| WO2016012471A1|2014-07-25|2015-07-22|Cooling of a metal strand portion|
    KR1020177005171A| KR102312840B1|2014-07-25|2015-07-22|Cooling of a metal strand portion|
    EP15744524.8A| EP3171998B1|2014-07-25|2015-07-22|Cooling of a metal strand portion|
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