EP0995523A1 - Vertical continuous casting plant with optimised molten metal level measuring - Google Patents

Abstract

The measuring apparatus consists of two physically different working measuring systems (22, 26) each with a sensor (24, 28). The sensors are fixed in a predetermined position with respect to the mold (10). The first measuring system (22) has a measuring precision of at least plus or minus 2 mm in a measuring region of at least 200 mm. The second measuring system (26) has a measuring precision of at least plus or minus 0.1 mm in a measuring region of at least 20 mm. Vertical continuous casting plant comprises a mold (10) with a moving floor (14) arranged on a sinking casting plate (16), a launder system (20) for transporting a metal melt from an oven into the mold, a measuring apparatus for determining a time-dependent metal melt level (N(t)), and a through-flow regulator (30) to control the metal supply in the mold depending on the difference of a prescribed theoretical value progression Nsoll(t) and the measured time-dependent metal melt level (N(t)). The measuring apparatus consists of two physically different working measuring systems (22, 26) each with a sensor (24, 28). The sensors are fixed in a predetermined position with respect to the mold (10). The first measuring system (22) has a measuring precision of at least plus or minus 2 mm in a measuring region of at least 200 mm. The second measuring system (26) has a measuring precision of at least plus or minus 0.1 mm in a measuring region of at least 20 mm.

Description

The invention relates to a vertical continuous casting system, in particular a vertical continuous casting system for the automatic continuous casting of aluminum alloys, comprising at least one mold with a start-up base arranged on a lowerable casting table, a pouring channel system for transporting a molten metal from an oven into the individual molds, and a measuring device for each mold for determining the time-dependent molten metal level N (t) and a flow control device for controlling the supply of metal in the individual molds depending upon the difference between a predetermined desired value curve _to N (t) and the measured time-dependent molten metal level N (t).

The invention further relates to a method for the vertical continuous casting of metals, in particular aluminum alloys, in a casting plant comprising at least one mold, in which method the liquid metal is fed from an oven via a trough system to the individual molds and via a flow control device into which one can be lowered Approach trays arranged at the casting table are first passed closed molds during a filling phase, starting from an initial level of the metal melt, at which metal melt level control begins, up to a predetermined level, at which the lowering of the casting table for producing the metal strands begins, and throughout lowering phase, the time-dependent metal level N (t) in each mold with a measuring apparatus and measured with a time-dependent setpoint _to N (t) is compared, and the metal supply in the individual ingot molds by means of a flow-through The control device is controlled according to the time-dependent difference between the actual and setpoint value of the metal level.

Such a method, as well as such a vertical continuous casting installation containing several molds are known for example from DE-OS 32 05 480 A1. According to the in DE-OS 32 05 480 A1 described teaching, the detection of the metal level is done by means of a float as a sensor that rests on the surface of the metal column and consists of a heat-resistant material, which must be selected so that a Absorption of molten metal or contaminants is avoided.

Patent EP-B 0 517 629 also describes a device described at the outset and describe a corresponding process for vertical continuous casting of metals, whereby to record the time-dependent molten metal level in the individual molds a capacitive sensor is used. The capacitive level measurement takes place between the surface of the molten metal and one to it at a certain distance located plate, which is at a distance from the metal surface by means of a servo motor is adjusted in such a way that the capacity is constant and equal to a reference capacity is.

In the case of a multi-strand continuous caster, this is particularly important for its trouble-free operation mastery of the starting process, i.e. the optimal control of the metal supply to the individual casting units until the actual casting start, which is achieved by lowering of the casting table is crucial. The metal level in the individual molds in the shortest possible time during the start-up phase to start lowering of the casting table to regulate the predetermined level without the risk of freezing consists of metal, WO 98/32559 describes a method according to which the metal level in all molds simultaneously according to a setpoint curve identical for all molds is regulated, its slope at the beginning of the regulation in comparison to the mean slope is greater and at the end of the start-up phase is smaller than the average gradient.

The filling level of the molds is typically at the beginning of the lowering process between 120 and 200 mm. The precise control of the metal level is particularly in the Lowering phase of crucial importance for a trouble-free operation of a Casting machine. The precise control of the metal level in the individual molds requires one correspondingly accurate measurement of the fill level. As a result, precise metal level control requires an accurate and reproducible level measurement over a large measuring range of typically 200 mm. The importance of a precise metal level determination is used in particular in the further developed controls of multi-mold continuous casting plants, such as in the case of controls according to WO 98/32559, where the level control is done with non-linear setpoint curves, greatly increased.

Inductive or capacitive sensors are suitable for the exact level determination. The However, the required accuracy can only be achieved in one with inductive sensors Reach measuring range of approx. 30-50 mm. The known from the prior art Vertical continuous casting plants therefore use most facilities where such Sensors using a precision mechanism in cooperation with a servo or Stepper motor are tracked in such a way that the required measurement accuracy allowed measuring range is not exceeded. Capacitive sensors can be used for gutters Measuring ranges of, for example, up to 300 mm can be used; however, they show one great dependence on the external measurement conditions, so that a frequent Recalibration is required.

For level and distance measurements, laser-optical, Ultrasound and Microwave process known.

Laser-optical methods can be used for level measurement of highly reflective measuring goods can only be used to a limited extent. Such methods are suitable in principle for level measurement of metal alloys, for example aluminum alloys, during the mold filling phase and at the beginning of the lowering phase. During the lowering phase forms after a few minutes - at least with aluminum alloys Beginning of the lowering phase a highly reflective oxide layer, which the use of laser optics Level measurement procedure severely impaired or even impossible.

Ultrasound and microwave methods based on the radar principle have a large one Measuring range and allow contactless level measurement, but do not show that required measurement accuracy, at least not for the lowering phase of the continuous casting process. In addition, the ultrasonic level measurement methods are strongly temperature-dependent, and that Microwave level measurement methods are sensitive to the measurement environment.

The invention is therefore based on the object of a vertical continuous casting plant at the beginning mentioned type with a precise, reliable and inexpensive level measurement to make available and to specify a method of the type mentioned at the outset, in which the metal level measurement is carried out in a simple manner with high precision can be.

According to the invention, the object on which the vertical continuous casting installation is based solved in that the measuring device from two physically different working Measuring systems with one sensor each, the sensors with respect to each measuring device the mold is fixed at a predetermined and fixed distance, and the first Measuring system with a measuring accuracy of at least 200 mm has at least ± 2 mm, and the second measuring system in a measuring range of at least 20 mm has a measurement accuracy of at least ± 0.1 mm.

The invention advantageously relates to vertical continuous casting plants with several molds. The However, the device according to the invention also comprises vertical continuous casting plants with only a single mold.

The solution according to the invention is based on the idea that at the start of the continuous casting process, i.e. during the first filling phase of those initially closed by the approach floor Chill mold, and during the remaining filling phase, as well as during the lowering process of the casting table different level measuring devices can be used, which the specific requirements during the different phases Take into account.

The invention is further based on the knowledge that a large measuring range of approximately 200 min only during the first filling phase of those initially closed by the start-up floor Chill mold is required, and in the subsequent filling and lowering phase of the casting table a smaller measuring range of, for example, 15-20 mm is sufficient. In addition is a less high measurement accuracy is required during the start phase than in the subsequent filling and lowering phase, since the filling level in the first filling phase is very different changed quickly. During the subsequent filling and lowering phase, however, is a very high measurement accuracy required.

The term measuring range means a measuring range in which the values as a whole Range between a maximum and a minimum measured value, where the difference between the maximum and the minimum value Measuring range corresponds. For example, the measured values are in a measuring range of 200 min in a value range between 0 and 200 mm.

A measuring device is preferred in which the first measuring system is based on an optical, capacitive, ultrasonic or microwave method, and the second measuring system based on an inductive, capacitive or optical method.

A measuring device in which the first measuring system is located on a optical or an ultrasonic or microwave method, and the second measuring system based on an inductive or capacitive process.

The first filling phase of the mold closed with the start-up floor usually takes place at the highest possible speed so that the metal level at the beginning of the Mold filling rises very quickly. This will cause the mold to start filling a turbulent flow is formed so that no flat at the beginning of the filling process Melt surface is present, which causes the reflective properties of the melt surface compared to a flat surface of the same metal turn out much smaller. For this reason, as well as those not yet formed in this phase of the process Oxide skin allows the first filling phase to be measured using a laser-optical level Method. For the subsequent casting process, i.e. during the rest of the filling phase and during the lowering process of the casting table, the use of a laser-optical is suitable Level measurement method due to the high reflection of the essentially flat Molten metal surface not for all alloys.

a) Ultraschall-Verfahren

b) Optische Verfahren

c) Mikrowellen-Verfahren nach dem Radar-Prinzip

d) Kapazitive Verfahren

According to the invention, the first measuring system can relate to sensors or sensors which are based on one of the level measuring methods described below:

a) Ultrasound procedure

b) Optical processes

c) Microwave method based on the radar principle

d) Capacitive processes

A level measurement with ultrasound is based either on the measurement of the runtime of a Sound pulse or on the measurement of sound absorption. The measurement of the Transit time of an ultrasonic pulse, i.e. the removal of the melt surface is from the transit time between the transmitted and received signal. That works Runtime procedure usually based on the principle of the echo sounder, i.e. an electrical impulse is, for example, by one on the start-up floor or on a lower area of the mold attached piezoelectric transducer converted into an ultrasonic pulse, which is emitted into the melt and from the melt-air boundary layer partially is reflected, the reflected ultrasound pulse (echo) to a similar piezoelectric transducer hits in which the echo turns into an electrical pulse is converted back. The fill level results from the transit time of the sound pulse and the speed of sound. The fill level can also be based on the same sonar principle measure when the ultrasonic transmitter and receiver are in the air space above the Melt surface is arranged. With ultrasonic level measurement has to Temperature of the media to be taken into account, since the speed of sound is temperature dependent.

When measuring the level with microwaves according to the radar principle Microwave transmitter and receiver as well as an antenna attached above the mold. The surface of the molten metal partially reflects that from the microwave transmitter emerging, usually frequency-modulated, electromagnetic waves or Impulses. The distance between the antenna and the melt surface is determined according to the Radar principle measured. In a preferred embodiment of this method, a Microwave signal emitted of constant amplitude and again after reflection received and mixed with part of the transmission signal; the frequency of the mixer output signal is proportional to the runtime and therefore a measure of the distance between the transmitter and the melt surface.

An optical level measurement can be an interferometric distance measurement, a laser runtime method or a triangulation procedure.

With the interferometric distance measurement the distance of the reflecting Melt surface measured by a sensor. Either the Phase angle difference between reflected and unreflected, modulated laser beam evaluated, or the displacement of the reflector surface is measured (Melt surface) with a counting laser interferometer. With interferometric Distance measurement is expediently a monochromatic laser beam split a semitransparent mirror into a measuring and a reference beam. Both beams are emitted by one reflector, one fixed and one movable, reflected. The reflected rays are superimposed on the semi-transparent mirror, creating interference fringes that are transverse to and from the receiver to be analyzed. A distance change of the melt surface of λ / 4 (λ = wavelength of the laser beam) causes a maximum change in the light intensity, see above that the change in melt level results from the number of registered maxima or minima and the wavelength.

In the laser transit time method, the level measurement can be carried out by a direct transit time measurement a light pulse or a phase measurement. During phase measurement the transmission signal is expediently converted to a carrier signal, for example in the MHz range, modulated, the measurement of the phase shift after demodulation in the receiver. The direct transit time measurement is based on the radar principle, in which smallest time differences in the nano to picosecond range can be measured.

In the triangulation process, the level measurement is traced back to an angle measurement. A highly focused beam of light from a laser hits under a pointed one Angle on the surface of the melt and is reflected on it. Depending on the level the reflected light beam strikes a certain point on the receiver, i.e. for example of a location detector. The position detector can be a CCD line, for example (Batch Coupled Device), which consist of a large number of light-sensitive components (pixels). With a CCD line this position can recorded and converted into the level using the angle or path difference. The Imaging location of the reflected laser beam on the position detector shifts into Dependence on the distance of the melt surface from the sensor.

With capacitive level measurement, the capacity is dependent on the melt height measured. The capacity changes, for example, through the degree of coverage or the distance between two given surfaces. However, the capacity changes also by changing the dielectric constant (e.g. the air) Introduction of the molten metal. A change in capacity is, for example, about demonstrated the change in capacitive resistance.

e) kapazitiv

f) induktiv

g) optisch

According to the invention, the second measuring system can relate to sensors or sensors which are based on one of the level measuring methods described below:

e) capacitive

f) inductive

g) optically

N =

Windungszahl

s =

Weglänge der magnetischen Feldlinien

A =

die von den magnetischen Feldlinien durchsetzte Fläche,

m =

Permeabilität des Materials.

The inductive sensors are preferably based on measuring the change in the inductive resistance X _L , with: X L = ωL, in which L = N 2nd · Μ · A s and

N =

Number of turns

s =

Path length of the magnetic field lines

A =

the area penetrated by the magnetic field lines,

m =

Permeability of the material.

According to the invention, the sensors are predetermined and in relation to the mold fixed distance, i.e. the two measuring systems have no device to adjust the height of the sensors.

Also preferred are measuring systems that have no mechanically moving parts, and in particular no mechanical precision parts. Measuring systems are further preferred, that work contactlessly in relation to the molten metal.

A measuring device for each casting unit (mold) is particularly preferred, in which the first measuring system on an optical method, in particular on a triangulation method, and the second measuring system is based on an inductive method.

A first measuring system with a measuring range of up to is very particularly preferred 200 mm, whereby a measuring accuracy of ± 1 mm is achieved in the whole measuring range.

The measuring accuracy of the first measuring system is typically between ± 0.1 mm and ± 2 mm, preferably between ± 0.1 mm and ± 1 mm.

The measuring range of the second measuring system is typically 20 to 50 mm, the Measuring accuracy typically between ± 0.01 mm and ± 0.1 mm, preferably between ± Is 0.01 mm and ± 0.08 mm.

The combination of an optical sensor with an inductive sensor allows provision a compact and powerful measuring device, which on the one hand does not expensive, sensitive and elaborately designed, mechanical sensor tracking devices required and on the other hand due to the measuring range and measuring accuracy an efficient level measurement for the individual casting phases the metal melt allows with sufficiently high accuracy. The inventive Continuous caster is particularly suitable for a control algorithm for Introducing metal into the individual molds, in which non-linear Setpoint curves can be used to control the level of molten metal.

By avoiding mechanical tracking devices of the sensors is also for the level measurement with respect to the vertical dimensions significantly less space needed so that the casting system can be built more compact.

In order to achieve the object of the method according to the invention, the Measurement of the time-dependent metal level N (t) with a measuring device consisting of two physically different working measuring systems is carried out, whereby starting from the initial level until reaching a predetermined melt level done by a first measuring system with a first sensor, and for the further Measurement of the time-dependent metal level curve N (t) during the subsequent one Filling and lowering phases a second measuring system with a second sensor is used, and the sensors of the two measuring systems with respect to the mold are fixed and take a constant position throughout the continuous casting process.

The filling phase begins with the introduction of liquid metal onto the start-up floor and ends with the start of lowering the start-up floor, ie when the start level N _{s is reached} at time t _s . The metal level control usually only begins when a certain metal level N _{a is reached} at time t _a in the mold, which is initially closed by the start-up floor. The first filling phase denotes the period from the start of the introduction of liquid metal into the mold until the time t _w , at which the change from the first to the second measuring system for the metal level determination takes place, where t _w denotes the time at which the metal level in the first a mold closed by the start-up floor reaches a predetermined height N _w . The period between t _w and t _s describes the second or the further filling phase, or that of the first filling phase that follows. The lowering phase begins when the start level N _{s is reached} at time t _s and lasts until the end or the termination of the continuous casting process.

The flow control device is a function of the difference of the measured metal level path N (t) of the setpoint curve N _soll (t) controlled by a control unit, said flow control device determines the current flowing into the mold molten metal amount. The control unit determines, for example, the start time t _{a of} the mold filling, the time t _w for changing the measuring system, the standard time t _{s of} the lowering process, the filling of the mold or the amount of metal to be introduced into the mold per unit of time during the filling phase and during the Lowering process, the lowering speed of the casting table and the control of the measuring system responsible for level measurement N (t). However, the control unit may also serve to monitor and control further process parameters, such as cooling water supply, CO ₂ supply, supply of refining agent, EMC power supply, and automatically initiate the lowering process of the casting table, for example.

In a preferred embodiment of the method according to the invention, the metal supply into the individual molds is only regulated directly up to the starting time t _s by the time-dependent difference between the actual and the setpoint value of the metal level. Furthermore, the direct control of the metal supply takes place after the start of the lowering process as a function of the bar length, ie as a function of the vertical casting table position, and on the basis of the difference between the actual and target value of the metal level. Accordingly, the control of the metal supply takes place after the start time t _s by the bar length-dependent difference between the actual and target value of the metal level. Since the lowering process usually takes place at a constant speed, the bar length increases linearly with time, so that the regulation of the metal supply is also regulated during the lowering process in accordance with the time-dependent difference between the actual and target value of the metal level.

The time t _{a of} the start of the level control is preferably determined by measuring the metal level, in particular by level measurement using a laser-optical method. The level measurement by means of the second measuring system, i.e. the time of the change of the measuring systems, can either be triggered by a control unit based on the measured metal level, or according to a preferred embodiment, in particular when using a second measuring system with an inductive measuring method, directly by the Melt levels are triggered by changing the measuring system at a time at which the melt enters, for example, the cavity formed by an inductively operating measuring coil.

The method according to the invention is suitable for casting plants with only one mold; in particular However, it is suitable for vertical continuous casting plants with several molds.

According to the invention, the sensors of the two measuring systems take one casting unit with regard to the mold, a fixed and constant one during the entire continuous casting process Position on, i.e. the measurement takes place without any mechanical tracking device in Form, for example, a height adjustment of the sensors. This is preferably done Level measurement during the first filling phase with regard to the metal melt without contact.

The measuring systems include continuously and discontinuously working Level detection systems. Accordingly, the inventive method can by a continuous and / or discontinuous level measurement can be carried out. In the Level measurement with the second measuring system is a continuous metal level measurement prefers. The measurement is preferably carried out with the first Measuring system at discrete points in time, in particular with 3 to 10 measured values, the Level measurement with the second measuring system is carried out continuously.

In casting plants with several molds, the lowering of the casting table begins with the Appropriately soils as soon as the start level is reached in a mold.

The metal level in the launder from the start of the filling phase is also preferred Approach floors and the molds on up to and with the stationary pouring phase (lowering phase) kept at a constant level.

Further advantageous developments of the method according to the invention result from the subclaims.

The continuous casting installation according to the invention and the method according to the invention are suitable for the casting of all continuously castable metals, but preferably for the continuous casting of Aluminum, magnesium and copper alloys. Those according to the invention are particularly suitable Continuous casting plant and the method according to the invention, however, for continuous casting of aluminum alloys.

Figur 1

zeigt schematisch einen vereinfachten Querschnitt durch einen Teil einer Kokille mit eingefahrenem Anfahrboden.

Figur 2

zeigt schematisch eine Sollwertkurve des zeitlichen Verlaufs des Metallniveaus in einer Kokille.

Further advantages, features and details of the invention result from the exemplary embodiments shown in FIGS. 1 and 2 and from the description of the figures.

Figure 1

shows schematically a simplified cross section through part of a mold with a retracted approach floor.

Figure 2

shows schematically a setpoint curve of the time course of the metal level in a mold.

The vertical continuous casting installation shown in FIG. 1 contains a mold 10 with a start-up floor 14 arranged on a lowerable casting table 16, a lifting / lowering device 11 for the casting table, which is driven by a motor 12, the motor being controlled by a control unit 34, a metal level measuring device consisting of two measuring systems 22, 26, a pouring channel system 20 for transporting a molten metal 18 from a furnace (not shown) into the mold 10, a flow control device 30 controlled by the control unit 34 determining the amount of molten metal to be introduced into the mold. The control unit 34 determines, inter alia, the starting time t _{a of} the mold filling, the starting time t _{s of} the lowering process, the filling of the mold or the amount of metal 18 to be introduced into the mold 10 per unit of time during the filling phase and during the lowering process and the lowering speed of the casting table 16 , wherein the control unit 34 operates as a function of the metal level measurement N (t) and a predetermined setpoint curve N _Soll (t).

The flow control device 30 shown by way of example in FIG. 1 essentially exists from an inlet opening 33 located in the trough 20, which is from a vertically movable plug 32 is closable. The plug 32 can be passed through on the one hand Lower it into the inlet opening 33 into the closed position, or by lifting it Opening cross section and thus the supply of molten metal 18 in the mold 10 accordingly be enlarged. The plug 32 has a stuffing rod, which by a Holding device guided and driven by a motor 31, the motor over the control unit 34 is controlled.

Before a casting begins, all settings on the Casting plant checked. When all starting conditions are met, tilting of the furnace containing the liquid metal, the casting trough 20 to a predetermined Metal level filled. As soon as a sensor - for example an inductive sensor - a Indicates predetermined fill level in the trough 20, the inlet opening 33 of the Watering trough 20 by lifting the plug 32 of the flow control device 30 released and the filling of the approach floors 14 and 10 molds with the liquid Metal 18 starts. The metal level N (t) takes place in the start-up base 14 or in the mold 10, for example PID-controlled, via a measuring device containing two measuring systems 22, 26.

The mold 10 shown in Figure 1 is shown in the closed state, i.e. the The mold 10 rests on the approach floor, the lowering process not yet having started. However, the filling phase is almost complete because the mold 10 is already close to second sensor 28 is filled with liquid metal 18.

The first sensor 24 is at a greater distance from the approach floor 14 than the second Sensor 28. This ensures that the on a laser optical Process based, first sensor 24 does not come into contact with the melt 18. The one on an inductive However, second sensor 28 based on the measurement method requires, at least in part, the direct contact with the melt 18.

The sensors 24 and 28 are at a fixed distance from the respective other measuring system 22 or 26 connected. In addition, the two measuring systems 22 and 26 are mechanical to one another firmly connected, i.e. The two measuring systems usually form one with the other mechanical unit.

The distance of the sensors 24, 28 from the mold is constant during the entire continuous casting process, ie the distance of the sensors 24, 28 from the metal surface changes constantly, in particular during the filling phase of the mold. Accordingly, at the beginning of the filling phase, the distance of the sensors 24, 28 from the molten metal surface, respectively. to the approach floor 14 is greatest, while this distance decreases continuously or discontinuously during the filling phase and remains essentially constant after reaching the start level N _s , ie at the beginning and during the lowering process.

The embodiment shown in the drawing relates to continuous casting with a conventional mold. The vertical continuous caster according to the invention however, also includes other casting methods, such as casting in an electromagnetic Alternating field (EMC), i.e. using an electromagnetic Mold.

2 shows an example of a setpoint curve N _to (t) for the inventive method. Once the metal in a mold 10, a predetermined initial level N _A at the start time t _A has been reached, the metal level control starts due to the setpoint curve N _soll (t) and the measured metal level N (t) to the metal level in the closed by the Anfahrboden 14 mold 10 has reached the start level N _s at the start time t _s , where the lowering of the casting table 16 for producing the metal strands begins.

grossere Steigung auf. Hingegen weist die Sollwertkurve N_soll(t) in einem gegen das Startniveau N_s naheliegenden Bereich eine gegenüber der mittleren Steigung kleinere Steigung auf.The setpoint curve N _soll (t) shown in FIG. 2 is polygonal and is suitable, for example, for discontinuous control of the metal level. In a range close to the initial level N _a , the setpoint curve N set (t) has a value that _is relative to the mean slope

greater incline. On the other hand, the setpoint curve N _to (t) in an up to the starting level N _s nearby area a with respect to the central pitch smaller pitch.

At the time t _w, the value N _SOLL (t _w) the amount N _w at the time t _w is the change from the first measurement system 22 to the second measuring system 26 instead. In the second measuring system 26 shown in FIG. 1, which is based on an inductive measuring method, the point in time t _{w is} determined by the entry of the melt into the cavity formed by an inductively working measuring coil. Accordingly, the metal height N (t) above the approach floor 14 during the first filling phase, ie until the filling height has reached the value N _w , is determined with the first measuring system 22, which has a large measuring range. After the time t _w , the metal height is determined with the second measuring system 26, the measuring range of which is smaller than the first measuring system 22, but has a high measuring accuracy. The high measurement accuracy is particularly important from time t _w , since thereafter the setpoint curve N _soll (t) is preferably flatter than the mean slope, and thus the metal supply to the individual casting units in a continuous casting installation having several molds 10 until the actual casting start t _s , which is initiated by lowering the casting table 16, can be optimally controlled.

The starting level N _s , ie the height of the surface of the liquid metal 18 above the approach floor 14 at the starting time t _s , is typically between 100 and 200 mm and in particular between 120 and 190 mm. Starting level t _a - the starting level N _s is typically reached within a time of 20 to 90 s or preferably within 25 to 45 s.

Claims (11)

Vertical casting machine, in particular vertical continuous casting machine for the automatic continuous casting of aluminum alloys, comprising at least one mold (10) with a start-up base (14) arranged on a lowerable casting table (16), a pouring channel system (20) for transporting a molten metal from a furnace into the individual molds (10) , For each mold (10), a measuring device for determining the time-dependent molten metal level N (t) and a flow control device (30) for controlling the metal supply into the individual molds (10) depending on the difference between a predetermined setpoint curve N _Soll (t) and the measured time-dependent molten metal level N (t),
characterized in that the measuring device consists of two physically different working measuring systems (22, 26) each with a sensor (24, 28), the sensors (24, 28) of each measuring device are fixed with respect to the mold (10) at a predetermined and fixed distance, and that the first measuring system (22) has a measuring accuracy of at least ± 2 mm in a measuring range of at least 200 mm, and the second measuring system (26) has a measuring accuracy of at least ± 0.1 mm in a measuring range of at least 20 mm. Vertical continuous caster according to claim 1, characterized in that the first Measuring system (22) on an optical, capacitive, ultrasonic or microwave method, and the second measuring system (26) on an inductive, capacitive or optical Process based. Vertical continuous caster according to claim 1 or 2, characterized in that the first measuring system (22) on an optical or an ultrasound or microwave method, and the second measuring system (26) on an inductive or capacitive Process based. Vertical continuous caster according to one of claims 1 to 3, characterized in that the first measuring system (22) is based on an optical method, in particular on a Triangulation method, and the second measuring system (26) on an inductive method based. Vertical continuous caster according to one of claims 1 to 4, characterized in that the first measuring system (22) of each measuring device in relation to the molten metal (18) works without contact. Method for vertical continuous casting of metals, in particular aluminum alloys, in a casting plant comprising at least one mold (10), in which method the liquid metal is fed from an oven via a trough system (20) to the individual molds (10) and via a flow control device (30 ) into the molds (10), which are initially closed on a lowerable casting table (16) arranged during a filling phase, starting from an initial level (N _a ) of the molten metal (18) at which a molten metal level control begins , up to a predetermined starting level (N _s ), at which the lowering of the casting table (16) for the production of the metal strands begins, and during the entire lowering phase the time-dependent metal level N (t) in each mold (10) is measured with and with a time-dependent setpoint specification N _soll (t) is compared, and the metal feed into the individual K okillen (10) is controlled by means of a flow control device (30) according to the time-dependent difference between the actual value and the target value of the metal level,
characterized in that the measurement of the time-dependent metal level N (t) is carried out with a measuring device consisting of two physically different measuring systems (22, 26), starting from the initial level (N _a ) until reaching a predetermined melt level (N _w ) by a first measuring system ( 22) with a first sensor (24), and a second measuring system (26) with a second sensor (28) is used for the further measurement of the time-dependent metal level curve N (t) during the subsequent filling and lowering phases, and the sensors (24, 28) of the two measuring systems (22, 26) occupy a fixed position with respect to the mold (10) and are constant during the entire continuous casting process. A method according to claim 6, characterized in that the first measuring system (22) on an optical, capacitive, ultrasonic or microwave process, and the second measuring system (26) on an inductive, capacitive or optical method based. A method according to claim 6 or 7, characterized in that the first measuring system (22) on an optical method, in particular on a triangulation method, and the second measuring system (26) is based on an inductive method. Method according to one of claims 6 to 8, characterized in that the predetermined melt level (N _w ), at which the measuring system change takes place, is determined by the vertical position of the lower opening of a cylindrical cavity formed by an inductively working measuring coil, wherein the longitudinal axis of the measuring coil is essentially perpendicular to the surface of the molten metal. Method according to one of claims 6 to 9, characterized in that the measurement of the metal level N (t) with the first measuring system (22) at discrete times takes place, and the metal level measurement N (t) with the second measuring system (26) continuously happens. Method according to one of claims 6 to 10, characterized in that the metal supply to the mold (10) _{is to} due to the corresponding difference between the setpoint curve N (t) and metal level measurement value N (t) PID-controlled takes place.

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