Patent Publication Number: US-11376655-B2

Title: Casting apparatus and casting method

Description:
TECHNICAL FIELD 
     The present invention relates to a casting apparatus for continuous or semi-continuous casting of metals using a pump to counter a metal flow induced by a gravitational force to control a flow of liquid metal more precisely and with less turbulence. 
     BACKGROUND 
     In continuous or semi-continuous casting, liquid metal is supplied into a mold cavity of a casting mold. In the mold cavity, the liquid metal at least partially solidifies into a cast product that exits the mold cavity via an open side of the mold cavity caused by a relative movement between the cast product and the mold. Semi-continuous casting is for example used to cast rolling ingots (ingots that are for example hot and cold rolled to produce rolled products such as sheet metal), forging ingots (ingots that are forged into forged products) or extrusion billets (billets that are for example extruded in an extrusion press to produce an extruded product). Continuous casting is for example used to continuously produce a rolled product without producing a rolling ingot that is hot rolled and cold rolled in separate production steps as an intermediate product. 
     A casting apparatus usually comprises a reservoir for holding and/or producing liquid metal such as a melting furnace or a melt tank for holding liquid metal that has been supplied to the melt tank from for example a melting furnace or an electrolysis process. 
     From the reservoir, the liquid metal is supplied into a mold cavity of the casting mold via a flow path that is for example implemented as a distribution launder. In the mold cavity, the liquid metal cools and at least partially solidifies. The cast product exits the mold cavity via an open side thereof caused by a relative movement between the mold and the cast product as mentioned above, for example by movement of a starter block. 
     A conventional casting apparatus is shown in  FIG. 1  and described in United States patent application US20100032455A1. As is apparent form  FIG. 1 , in the conventional casting apparatus, liquid metal is supplied from a reservoir via a flow path  1  (here shown in a sectional view and implemented as a launder) into the mold cavity  2  of a mold  3 . The flow path  1  comprises an outlet, here implemented as a nozzle,  4  through which the liquid metal exits the flow path  1  and flows into the mold cavity  2 . The driving force for the flow of the liquid metal is gravity. To control the flow of the liquid metal, there is provided a pin assembly  5 , that can increase or decrease the effective cross-sectional area available for the liquid metal to flow through the nozzle  4  by a vertical movement of the pin assembly to thereby control the volumetric flow rate of the liquid metal from the flow path  1  into the mold cavity  2 . The cast product exits the mold cavity  2  via a downwards movement of a starter block  6 . 
     It is desirable to have a casting apparatus and a casting method that have a less turbulent liquid metal feeding system and allow production of cast products with improved properties such as improved surface quality. 
     Short Description of the Invention 
     The inventor has found that the quality of a cast product (also known as casted product) strongly depends on a precise control of the level of liquid metal in the mold cavity so the level of liquid metal in the mold cavity corresponds to a predetermined value despite the relative movement between the mold and the cast product during the continuous or semi-continuous casting operation. The inventor has found that a low metallostatic pressure (see p in  FIG. 2 ) in the mold cavity and a laminar flow of the liquid metal when the liquid metal enters the mold cavity improve the quality, in particular the surface quality, of the cast product. In the conventional apparatus describe above, a precise control of the metal level in the mold cavity is difficult due to the movement of the pin assembly. Further, the conventional casting apparatus generates a turbulent flow of the liquid metal, because the effective flow cross section is reduced and a flow velocity increases according to the Venturi effect. The turbulent flow may result in oxidation of the liquid metal to be cast and quality problems of the cast product 
     In this respect, in order to avoid or alleviate the afore-mentioned problems, an aspect of the present invention provides a casting apparatus for continuous or semi-continuous casting (e.g. vertical direct chill casting) of a cast product comprising a reservoir for supplying liquid metal, a direct chill casting mold having a mold cavity for at least temporarily holding liquid metal and to at least partially solidify the liquid metal into a cast product, wherein a flow path for the liquid metal is defined between the reservoir and the mold cavity, and wherein the casting apparatus is configured such that the liquid metal has a tendency to flow along the flow path from the reservoir into the mold cavity by gravity, wherein the liquid metal enters the mold cavity via a first vertically higher side of the mold, and wherein the cast product exits the mold via a second vertically lower side of the mold, and a pump disposed on the flow path between the reservoir and the mold cavity, wherein the pump is operable to generate a force in the liquid metal that is acting against the tendency of the liquid metal to flow along the flow path from the reservoir into the mold cavity by gravity to control a flow of the liquid metal from the reservoir into the mold cavity. The cast product may exit the mold in a rectilinear manner via the second side of the mold in a straight vertical direction. A longitudinal axis of the cast product may be continuously rectilinear from the at least partial solidification until the full solidification. The cast product may be an extrusion ingot or a rolling slab. 
     According to the invention, a larger cross-sectional area for the flow of liquid metal along the flow path can be provided than in the conventional casting apparatus while a controllability of the flow of the liquid metal is improved. The larger cross-sectional area may result in a less turbulent and more laminar flow of the liquid metal. For example, a minimum flow cross-sectional area at an outlet of the flow path according to the invention may be 2000 mm 2  (square millimeter), which is significantly larger than in the conventional casting apparatus using a pin assembly to control the flow of the molten metal. According to the invention, the flow of the liquid metal from the reservoir into the mold cavity is driven by gravity and the pump is used to limit the flow by generating a force acting in a direction opposite to the flow direction without changing the flow direction. In other words, according to the invention, the pump may be used as a flow regulator. According to the invention, the pump may be used to completely stop the flow of liquid metal from the reservoir into the mold cavity. 
     According to embodiments of the invention, the casting apparatus may further comprise a sensor for detecting a level of liquid metal in the mold cavity and for outputting a level value indicative of the level of liquid metal in the mold cavity, and a controller, wherein the sensor and the pump may be operably connected with the controller, and wherein the controller may be configured to operate the pump based on the level value and a predetermined set value indicative of a desired level of the liquid metal in the mold cavity such that a difference between the level value and the set value is minimized. 
     According to embodiments of the invention, the first side of the mold may be sealed and a gas atmosphere between the liquid metal in the mold cavity and the first side may be controlled such as to control oxidation of the liquid metal in the mold cavity. 
     According to embodiments of the invention, the sensor may be a radar sensor that emits electro-magnetic radar radiation having for example a frequency of 80 GHz or higher that may be incident on the liquid metal in the mold cavity in a radar radiation area. According to embodiments, the sensor may be a laser distance sensor, a capacitive distance sensor or an ultrasonic distance sensor. Particularly good results may be achieved with the radar sensor having a radar frequency of 80 GHz or higher, as the electromagnetic radar radiation having such a radar frequency may penetrate through smoke and dirt that may be present in the mold cavity between the sensor and the surface of the liquid metal. 
     According to embodiments of the invention, there may be provided an at least partially radar radiation transparent body in a radar beam path between the radar sensor and the liquid metal in the mold cavity, wherein the at least partially radar radiation transparent body may have two outer surfaces that each may have a normal vector that is not parallel to a straight line between the sensor and the liquid metal in the mold cavity in the radar radiation area to avoid or reduce detection of radar radiation reflected by the at least partially radar radiation transparent body with the radar sensor. 
     According to embodiments of the invention, the at least partially radar radiation transparent body may be provided integrally with the closed first side of the mold. 
     According to the invention, the pump is an electromagnetic pump, in particular a direct current electromagnetic pump. An electromagnetic pump is particularly efficient as it allows a precise and delay-free control of the flow of the liquid metal due to the lack of moving mechanical parts. 
     According to embodiments of the invention, the controller may be configured to change the predetermined set value during a casting operation of the cast product. 
     According to embodiments of the invention, the controller may be configured to change the predetermined set value from a value indicative of a higher level of the liquid metal in the mold cavity earlier in the casting operation of the cast product to a value indicative of a lower level of the liquid metal in the mold cavity later in the casting operation of the same cast product. 
     According to embodiments of the invention, the mold may comprise means for active cooling of the cast product such as a cooling water nozzle for spraying water on the cast product that is exiting the direct chill casting mold cavity via the second side. 
     According to the invention, the liquid metal isliquid aluminium or aluminium alloy and the cast product is an aluminium or aluminium alloy product. 
     According to the invention, a flow diverter is provided on the flow path downstream of the pump to direct at least a portion of the liquid metal in a predetermined direction in the mold cavity. The flow diverter may be configured such that the portion of the liquid metal is directed into a direction that is not the vertical direction. For example, the flow diverter may comprise a tubular structure having a cross-section (through which the liquid metal may flow into the mold cavity) defining a flow path for the liquid metal that has a longitudinal central axis that has a direction that deviates from the vertical direction. Said cross-section may change, e.g. continuously change, along the flow path in an upstream-downstream direction from a rectangular, e.g. quadratic, cross-section towards a rectangular cross-section neighboring the outlet of the flow diverter. This is particularly useful if the cast product is a rolling slab. The cross-section may change, e.g. continuously change, along the flow path in an upstream-downstream direction from a rectangular, e.g. quadratic, cross-section to a circular cross-section neighboring the outlet of the flow diverter. This is particularly useful if the cast product is an extrusion billet. The flow diverter may be configured such that at least a portion of the liquid metal is directed into a direction that has a horizontal component. 
     According to a further aspect of the invention, there is provided a method for continuous or semi-continuous casting of a cast product using the apparatus described above, the method comprising supplying liquid metal from a reservoir into a mold cavity of a direct chill casting mold along a flow path defined between the reservoir and the mold cavity by using, for example exclusively, a gravitational force, and generating a force acting on the liquid metal using a pump that acts against the flow of the liquid metal along the flow path caused by the gravitational force to control supply of the liquid metal into the mold cavity to thereby control a level of liquid metal in the mold cavity. 
     According to embodiments of the invention, the method may further comprise calculating a set value indicative of a desired level of the liquid metal in the mold cavity, measuring an actual value indicative of the actual level of liquid metal in the mold cavity, and controlling generating the force using the pump such that a difference between the set value and the actual value is minimized during a casting operation. 
     According to embodiments of the invention, generating the force using a pump may comprise generating an electromagnetic field acting on the liquid metal that results in a force having a direction opposing a flow of the liquid metal along the flow path. 
     All embodiments and features of the invention may be combined with each other. Features relating the apparatus also relate to the method and vice versa. 
    
    
     
       SHORT DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a view of a casting apparatus according to conventional technology. 
         FIG. 2  shows a schematic view of a casting apparatus according to an embodiment of the invention. 
         FIG. 3  shows a schematic view of a flow path according to an embodiment of the invention. 
         FIG. 4  shows a schematic sectional view along line A-A in  FIG. 2  of a direct current electromagnetic pump according to an embodiment of the invention. 
         FIG. 5  shows a schematic view of a casting apparatus according to a further embodiment of the invention. 
         FIG. 6  shows a schematic view of a casting apparatus according to a further embodiment of the invention. 
         FIG. 7  shows a schematic view of a casting apparatus according to an embodiment of the invention comprising a flow diverter. 
         FIG. 8  shows a schematic view of a casting apparatus according to an embodiment of the invention comprising a controller. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the invention. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention to those exemplary embodiments. 
     With reference to  FIG. 2 , a casting apparatus  10  according to the invention comprises a reservoir  15 . The reservoir  15  may supply liquid metal  20 . For example, the reservoir may be a melting furnace or a distribution lauder or any other means for storing and/or producing liquid metal  20 . 
     The liquid metal  20  may be liquid aluminium, liquid aluminium alloy, liquid steel or any other liquid metal. 
     The casting apparatus  10  further comprises a direct-chill casting mold  25 . The casting mold  25  comprises a mold cavity  30  for receiving the liquid metal  20 , for at least temporarily holding the liquid metal  20  and to at least partially solidify the liquid metal  20  into a cast product  35 . The mold cavity  30  may be surrounded on the lateral sides thereof by a mold frame  40  of the casting mold  25 . The cast product  35  may for example be a rolling ingot, an extrusion billet, a T-bar, or any other cast product  35 . 
     The casting mold  25  may have a first, vertically higher side  26  and a second, vertically lower side  27 . The liquid metal  20  may enter the mold cavity  30  via/through the first side  26 . The liquid metal  20  may at least partially solidify in the mold cavity  30  to produce the cast product  35 .  FIG. 2  schematically shows liquid metal  20 , a zone of partially solidified metal  21  in which the solidification takes place, and solidified metal  22  in the mold cavity. The cast product  35  may exit the mold cavity  30  via the second side  27  via a relative movement between the cast product  35  and the casting mold  25 . The casting process of a cast product  35  may take place in a steady-state process in which—optionally after an non-steady-state initialization process—the spatial location of the zones corresponding to liquid metal  20 , partially solidified metal  21  and solidified metal  22  remain stationary while the cast product  35  is produced and continually moved in a downwards direction while new liquid metal  20  is supplied into the mold cavity  30  from the reservoir  15   
     The casting mold  25  may comprise means for active cooling of the liquid metal  20  in the mold cavity  30  and/or for active cooling the partially solidified metal  21  and/or for active cooling of the cast product  35 . In  FIG. 2 , the means for active cooling are implemented by a hollow water channel  45  in the mold frame  40 . The means for active cooling in  FIG. 2  further comprise an aperture  50  provided in the mold frame  40  such that water may exit the hollow water channel  45  via the aperture  50  and come into contact with the cast product  35  such as to cool the cast product  35 . For cooling, water may be supplied into the hollow water channel  45 , may cool the liquid metal  20  in the mold cavity  30  via heat transfer through the mold frame  40  and may also exit the hollow water channel  45  via the aperture  50  to directly cool the cast product  35 . In  FIG. 2 , the water that is directly cooling the cast product  35  is schematically shown by the wavy area on the lateral sides of the cast product  35 . 
     With further reference to  FIG. 3 , the casting apparatus  10  may comprise a flow path  55  that is defined between the reservoir  15  and the mold cavity  30 . The flow path  55  may be configured such as to define a fluid connection between the reservoir  15  and the mold cavity  30  so that the liquid metal  20  can flow from the reservoir  15  into the mold cavity  30 . The casting apparatus  10  may be configured such the liquid metal  20  has a tendency to flow from the reservoir  15  into the mold cavity  30 . The tendency may be caused by gravity as shown by the arrow labeled g in  FIG. 2  that symbolizes a vector representing gravity. The flow path  55  may be implemented as flow conduit or flow pipes or flow channel. 
     With reference to  FIGS. 2 and 3 , the casting apparatus  10  according to the invention comprises a pump  60  disposed on the flow path  55  between the reservoir  15  and the mold cavity  30 . The pump  60  may be operated to produce a force acting on the liquid metal  20  that at least partially (and as a maximum fully) counters the tendency of the liquid metal  20  to flow from the reservoir  15  into the mold cavity  30 . Accordingly, the flow rate of the liquid metal  20  from the reservoir  15  into the mold cavity  30  may be controlled (e.g. by limiting the flow induced by gravity) by the pump  60 . The pump  60  may be operated or configured such that the maximum force generated by the pump  60  substantially stops the flow of the liquid metal  20  from the reservoir  15  into the mold cavity  30  but does not reverse the flow direction. The force generated by the pump  60  is schematically indicated by the arrow pointing upwards in  FIGS. 2 and 5 to 8 . By operation of the pump  60 , a level h of the liquid metal  20  in the molt cavity  30  may be controlled. The inventor has found that the quality of a cast product  35  is strongly dependent on a precise control of the metal level h during the casting operation. The arrow between the pump  60  and the mold cavity  30  that is shorter than the arrow between the reservoir  15  and the pump  60  in  FIG. 3  schematically indicates the control, implemented by a reduction of the flow rate induced by gravity, of the liquid metal  20  from the reservoir  15  into the mold cavity  30 . 
     The pump  60  may for example be an electromagnetic pump, in particular a direct current (DC) electromagnetic pump of the induction type without moving parts as schematically shown e.g. in  FIGS. 2 and 4 . Such a pump is herein also referred to simply as DC electromagnetic pump in the following. A DC electromagnetic pump  60  is particularly advantageous in the casting apparatus  10  according to the invention as it allows a very precise control of the flow of the liquid metal  20  due to a high responsiveness (that is, a short time delay between an input signal to the pump  60  and a resulting force acting on the liquid metal  20  generated by the pump  60 ) and good controllability (the amount of force generated by the pump  60  can be precisely controlled via a control of the electric current supplied to the pump  60 ).  FIG. 4  shows a schematic sectional view of a DC electromagnetic pump  60  along line A-A in  FIG. 2 . With reference to  FIG. 4 , a DC electromagnetic pump  60  may comprise a casing  61  defining a lumen that forms a section of the flow path  55 . The DC electromagnetic pump  60  may further comprise a permanent magnet  65  with magnetic north pole N and magnetic south pole S arranged at opposite lateral sides of the flow path  55 . The electromagnetic pump  60  may further comprise two electrodes  70  that are arranged on lateral sides of the flow path  55  such that the two electrodes  70  are arranged perpendicular to a line between the north pole N and the south pole S of the permanent magnet  65 . Operating the electrodes  70  by applying electric voltage to them that will initiate an electric current through the liquid metal  20  inside the casing  61  along the flow path  55  from the reservoir  15  into the mold cavity  30  that generates a Lorentz force in the liquid metal  20 , wherein the Lorentz force counters the tendency of the liquid metal  20  to flow from the reservoir  15  into the mold cavity  30  by gravity. This results in a controllable reduction or increase (by reducing a force generated by the pump  60 ) of the flow rate from the reservoir  10  into the mold cavity  30  allowing in turn dynamic control of the level h of liquid metal  20  in the mold cavity  30  during a casting operation. 
     According to embodiments of the invention and with reference to  FIG. 5 , the first, vertically higher side  26  of the mold  25  may be provided at least partially, e.g. fully, gas-tight such as to separate the atmosphere in the mold-cavity  30  from the atmosphere surrounding the casting apparatus  10 . For example, there may be provided a casing or a removable lid (in  FIG. 5  exemplarily referenced with reference sign  80 ) in order to at least partially, e.g. fully, close the first side  26  of the mold  25  such as to separate the atmosphere inside the mold cavity  30  from the atmosphere surrounding the casting apparatus  10 . The atmosphere surrounding the casting apparatus  10  may for example be ambient air in a cast house. The casting apparatus  10  may further comprise means to control the atmosphere inside the mold cavity  30 , for example to control oxidation of the liquid metal  20  in the mold cavity. The means to control the atmosphere inside the mold cavity  30  may for example be implemented by a gas injection system to create an inert or reducing gas atmosphere inside the mold cavity  30 . 
     With reference to  FIG. 6 , the casting apparatus  10  may further comprise a sensor  75  for detecting the level h of liquid metal in the mold cavity  30  and for outputting a level value indicative of the level h of liquid metal  20  in the mold cavity  30 . The sensor  75  may for example be a laser distance sensor, a capacitive distance sensor or a radar distance sensor. For example, the sensor  75  may be a radar sensor that emits electromagnetic radar radiation with a frequency of 80 Ghz or higher. The electromagnetic radiation  76  that is emitted from the sensor  75  may be incident on the liquid metal  20  in the mold cavity  30 , may be reflected by the surface of the liquid metal  20 , and the reflected radar radiation may be detected by a detector in the sensor  75 . In  FIG. 6  only the radiation  76  emitted from the sensor  75  is shown and referenced with reference sign  76  for better clarity. The level h of the liquid metal  20  in the mold cavity  30  may then be calculated via a time or phase difference between the emitted and the received electromagnetic radar radiation  76 . A sensor  75  using radar radiation with a frequency of 80 GHz or more has been found to be particularly efficient, as radar radiation  76  with such a frequency can penetrate through smoke and solid deposits and thereby allow a more precise measurement of the metal level h in the mold cavity  30 . 
     The sensor  75  (not shown in  FIG. 5 ) may be provided inside the mold cavity  30  and at least partially vertically below the lid or casing  80 . The sensor  75  may also be provided vertically above the lid or casing  80  and may emit and receive a signal to measure the level h of the liquid metal  20  via an aperture (e.g. an aperture that is transparent for a sensor signal but non-permeable for gas) in the lid or casing  80 . 
     According to embodiments of the invention, in particular when the sensor  75  is implemented as a radar sensor (for example one with a radar frequency of 80 GHz or higher), and with reference to  FIG. 6 , the casing or removable lid  80  may comprise an at least partially radar radiation transparent body  85 , e.g. a partially radar radiation transparent body, in a radar beam path between the radar sensor  75  and the liquid metal  20  in the mold cavity  30 . The at least partially radar radiation transparent body  85  may have two (outer) surfaces  85   a ,  85   b  that each have a normal vector that is not parallel to a straight line between the sensor and the liquid metal  20  in the mold cavity  30  in the radar radiation area  85   c  to avoid detection of radar radiation reflected by the at least partially radar radiation transparent body  85  with the radar sensor  75 . The radar radiation area  85   c  is the area on the surface of the liquid metal  20  in the mold cavity  30  that is exposed to radar radiation form the radar sensor  75 . By using a configuration as described above and shown in  FIG. 6 , the detection precision can be improved as the radar sensor  75  does not detect radar radiation that is reflected by the at least partially radar radiation transparent body  85  while at the same time the atmosphere inside the mold cavity  30  may be separated from the atmosphere surrounding the casting apparatus  10  as described with reference to  FIG. 5 . The at least partially radar transparent body  85  may for example be made of glass and/or may be integrally provided with the casing or removable lid  80 . 
       FIG. 7  shows a further embodiment of the invention. The casting apparatus  10  according to the invention may comprise a flow diverter  90  that is provided on the flow path  55  downstream of the pump  60  to direct at least a portion of the liquid metal  20  in a predetermined direction in the mold cavity  30 . The two arrows in  FIG. 7  schematically show how at least a part of the liquid metal  20  flowing into the mold cavity  30  is diverted by the flow diverter  90  to predetermined directions in the mold cavity  30 . The flow diverter  90  may for example optimize the inflow of liquid metal  20  into the mold cavity  30  and the temperature distribution in the mold cavity  30 , in particular when the mold  25  has a non-symmetric shape when seen along the vertical direction (that is a direction from the first side  26  towards the second side  27  of the mold  25 ). The flow diverter  90  may for example be provided if the mold  25  has a rectangular shape, T-bar shape or any other non-symmetric shape when seen in the vertical direction. 
     With reference to  FIG. 8 , the casting apparatus  10  may comprise a controller  95 . The controller  95  may for example be implemented as an electronic control unit. The controller  95  may be operably connected with the pump  60  to control a pump function of the pump  60 . Optionally, if the casting apparatus  10  comprises a sensor  75 , the controller  95  may in addition be operably connected with the sensor  75 . The controller  95  may be configured to operate the pump  60  based on the level value h measured by the sensor  75  (actual value) and a predetermined set value indicative of a desired level h of the liquid metal  20  in the mold cavity  30 , such that a difference between the actual value and the set value is minimized. That is, the controller  95  may be configured to control the level h of liquid metal  20  in the mold cavity  30  according to an intended value (the set value) by operating the pump  60  based on a signal from the sensor  75 . The controller  95  may for example operate according to an PID control algorithm or any other algorithm that uses proportional (P) and/or integral (I) and/or derivative (D) (closed-loop) feedback control. 
     The controller  95  may be configured to change the predetermined set value from a value indicative of a higher level h of the liquid metal  20  in the mold cavity  30  earlier in the casting operation of the cast product  35  to a value indicative of a lower level h of the liquid metal  20  in the mold cavity  30  later in the casting operation of the cast product  35 . That is, the set value may be changed, e.g. during an initialization phase of a casting operation of a cast product  35  before the casting operation reaches a steady state operation. It has been found that such a change of the predetermined set value may result in a better quality of the cast product, as a preset filling rate of the mold cavity during the initial phase of casting and a gradual reduction of the metal level as the casting speed is increased during the early phase of casting toward a steady-state situation where the casting parameters and the metal level is kept constant until the end of cast. 
     In light of the above, a method for continuous or semi-continuous casting of a cast product  35  according to the invention may comprise supplying liquid metal  20  from the reservoir  15  into the mold cavity  30  of the direct chill casting mold  25  along a flow path  55  defined between the reservoir  15  and the mold cavity  30  by using a gravitational force, and generating a force acting on the liquid metal  20  using the pump  60  that acts against the flow of the liquid metal  20  along the flow path  55  caused by the gravitational force to control supply of the liquid metal  20  to the mold cavity  30  to control a level h of liquid metal  20  in the mold cavity  30  during casting of the cast product  35 . 
     The method may further comprise calculating a set value indicative of a desired level h of the liquid metal  20  in the mold cavity  30 , measuring an actual value indicative of the actual level h of liquid metal  20  present in the mold cavity  30  using the sensor  75 , and controlling generating the force using the pump  60 , for example a direct current electromagnetic pump  60 , such that a difference between the set value and the actual value is minimized. The generating the force using the pump  60  may comprise generating an electromagnetic field acting on the liquid metal  20  that results in a force having a direction opposing a flow of the liquid metal  20  along the flow path  55 . The method described herein may be carried out using the casting apparatus  10  according to embodiments of the invention. 
     All embodiments described herein may be combined with each other unless specified otherwise. Features described with respect to the casting apparatus  10  also apply as corresponding method steps for the method described herein and vice versa.