Patent Publication Number: US-11654478-B2

Title: Casting equipment

Description:
TECHNICAL FIELD 
     The present invention relates to casting equipment allowing a precise control of a metal level in a distribution reservoir that is in fluid connection with a casting apparatus for producing a cast product to thereby enable casting cast products with high quality and high efficiency. 
     BACKGROUND 
     Casting equipment generally comprises a source for molten metal, e.g. a furnace, a casting apparatus for solidifying molten metal while giving it an intended shape, a conduit for transporting molten metal from the source to the casting apparatus and a flow control means to adjust, e.g. interrupt, a flow of liquid metal from the source to the casting apparatus to control the casting operation. 
     Patent application publication US20100032455A1 describes such a casting equipment having flow control means implemented by a valve having a moveable pin. US patent publication U.S. Pat. No. 2,742,492 describes an apparatus for controlling the flow of molten metal using an electro-magnetic field to control gravity-induced metal flow from a tundish into a casting mold. 
     WO 2009/072893 A1 discloses an arrangement related to equipment for continuous or semi-continuous casting of metal, in particular DC casting of aluminium. The apparatus comprises a supply channel and a distribution chamber for distributing the metal to the moulds. A metal lifting container is arranged in connection with the supply channels. Metal is sucked into the metal lifting container and lifted to a level that is higher than the level of the distribution chamber above the moulds. The metal lifting container is sealed from the surroundings and has a connection to a vacuum source. 
     U.S. Pat. No. 3,552,478 discloses a method for starting and maintaining the supply of metal to a downward operating continuous casting mould where molten metal is sucked through a suction pipe from a reservoir into a closed launder disposed above and connected to an air suction device. 
     GB 1,082,413 discloses an apparatus for vacuum degassing of molten metal, in particular steel. The apparatus further comprises an evacuation container into which leads a suction lift nozzle from a melt container and from which evacuation container leaves a discharge nozzle connected to a pouring jet degasifying chamber. For transportation of metal through the degassing apparatus, an electric pump can be provided. 
     However, a more efficient casting equipment allowing better control of a metal level is desirable. 
     SHORT DESCRIPTION OF THE INVENTION 
     The present invention provides a casting equipment for casting melt into a cast product comprising a supply reservoir for supplying the melt, a distribution reservoir, a casting apparatus having a melt inlet connected to the distribution reservoir for producing the cast product, a supply conduit fluidly connecting the supply reservoir and the distribution reservoir, an electromagnetic pump provided on the supply conduit and operable to generate a force in the melt in the supply conduit, a level sensor for measuring a level of the melt in the distribution reservoir and/or in the supply reservoir and for outputting a corresponding level signal, a controller operably connected to the pump and the level sensor, wherein the supply conduit is sealed or sealable from a pressure of the atmosphere, wherein the controller is configured to control an operation of the pump based on the level signal from the level sensor, and wherein, at least during a steady-state casting operation, the casting equipment is configured such that the supply conduit defines a flow path that has a point a 1  that is higher than a surface of the melt in the supply reservoir and/or the distribution reservoir, and the pump is operated by the controller so that the metal level in the distribution reservoir is at an intended level such as to control a pressure of the melt in the melt inlet of the casting apparatus. In other words, the level is maintained in accordance with a level predefined for the actual casting operation. This may be static or may vary during the casting operation. 
     According to embodiments of the invention, the supply reservoir and the distribution reservoir are in direct fluid connection via a bypass valve that can be opened and closed, wherein the bypass valve is optionally implemented as a gate valve or dam. 
     According to embodiments of the invention, the supply reservoir, the supply conduit and the distribution reservoir form a supply siphon. 
     According to embodiments of the invention, the casting equipment may further comprise a shut-off valve that can be closed to interrupt a flow of the melt from the distribution reservoir to the casting apparatus, wherein the shut-off valve is optionally implemented as a gate valve or dam. 
     According to embodiments of the invention, the electromagnetic pump may be a direct current electromagnetic pump. 
     According to embodiments of the invention, at least during the steady-state casting operation, a level of the melt in the supply reservoir may be higher than the level of the melt in the distribution reservoir and the pump may be operated to generate a force that is at least partially countering a flow of melt from the supply reservoir to the distribution reservoir via the supply conduit in order to control a flow rate of melt from the supply reservoir to the distribution reservoir. 
     According to embodiments of the invention, at least during the steady-state casting operation, a level of the melt in the supply reservoir may be lower than the level of the melt in the distribution reservoir and the pump may be operated to generate a force that generates a flow of melt from the supply reservoir to the distribution reservoir via the supply conduit in order to control a flow rate of melt from the supply reservoir to the distribution reservoir. 
     According to embodiments of the invention, at least during the steady-state casting operation, the bypass valve may be closed and the shutoff valve may be open. According to embodiments of the invention, the melt may be molten aluminium or aluminum alloy. 
     According to embodiments of the invention, the casting apparatus may be a DC casting apparatus for continuously or semi-continuously casting, comprising at least one casting mold having an inlet for melt and an outlet for the at least partially solidified cast product, at least one starter block that is vertically moveable with respect to the at least one casting mold for supporting the cast product exiting the at least one casting mold, a distribution conduit that fluidly connects the distribution reservoir and the inlet of the at least one casting mold. 
     According to embodiments of the invention, at least during a steady-state casting operation, the casting equipment is configured such that the distribution conduit defines a flow path that has a point a 2  that is higher than a surface of the melt in the casting mold and the surface of the melt in the distribution reservoir, wherein at least the distribution conduit is sealed or sealable from the pressure of the atmosphere, wherein the distribution reservoir, the distribution conduit and the at least one casting mold from a distribution siphon such that a metallostatic pressure of a surface of the melt in the distribution reservoir is equal to the metallostatic pressure of the surface of the melt in the mold. 
     According to embodiments of the invention, the supply conduit and/or the distribution conduit may be configured to be evacuated to generate an, with respect to the atmosphere surrounding the casting equipment, under pressure therein. 
     Pressures and heights and levels described herein are to be understood as relative pressures and heights and levels unless described to the contrary. 
     Other features, aspects, implementations, and advantages will become apparent from the description, the drawings, and other specifications of the invention. 
    
    
     
       SHORT DESCRIPTION OF THE FIGURES 
         FIG.  1    shows a schematic view of a casting equipment according to embodiments of the invention, 
         FIG.  2    shows a schematic view of a casting equipment according to embodiments of the invention, 
         FIG.  3    shows a schematic view of a casting equipment according to embodiments of the invention, wherein the casting apparatus is implemented as a DC casting apparatus. 
     
    
    
     The figures are schematic and not necessarily to scale. 
     DETAILED DESCRIPTION 
       FIG.  1    shows a schematic view of a casting equipment  1  according to embodiments of the invention. The casting equipment  1  comprises a supply reservoir  10  for supplying melt (liquid metal)  15 . The supply reservoir  10  may for example be implemented as a static, e.g. not tiltable and not moveable, melting furnace that can heat metal such that the metal melts. The supply reservoir  10  may also be implemented as a holding tank that is filled with liquid metal/melt  15  to temporarily store the liquid metal  15 . The supply reservoir  10  may also be implemented as a holding furnace (i.e. a furnace that keeps the melt at an intended temperature but does not melt metal into melt) that stores the liquid metal  15 . 
     Said holding furnace and holding tank may be static, e.g. not tiltable and not moveable. The supply reservoir  10  may also be implemented as a moveable container, such as a melting pot or crucible. In this case, the movable container is filled with melt  15  and is then moved to a location in proximity of an inlet  31  of a supply conduit  30  as described further below. In particular if the supply reservoir  10  is implemented in a static manner, e.g. as a melting furnace or holding tank, carrying out the casting process has been found to be much safer, as the casting equipment  1  according to the invention has a much-reduced potential for leakage of melt compared to using a moveable pin to control the metal level in a launder. Leakage of melt should be avoided, as this may result in melt spills on the floor of a cast house that may give rise to explosions. 
     The casting equipment  1  further comprises a distribution reservoir  20 , also referred to as launder. The distribution reservoir  20  may temporarily hold melt  15  and supply it to a casting apparatus  25 . An outlet of the distribution reservoir  20  may be fluidly connected to an inlet of the casting apparatus  25 . The casting apparatus  25  may for example be a continuous casting apparatus, a semi-continuous casting apparatus as described below or any other casting apparatus that solidifies molten metal while giving it a predetermined shape. The distribution reservoir  20  may be fluidly connected to one or more casting apparatus  25  of the same or of different types. 
     During casting, melt  15  is supplied from the distribution reservoir  20  to the casting apparatus  25 . However, in order to achieve good quality cast products, a metal level h 3  in the distribution reservoir  20  must be precisely controlled, as the metal level h 3  in the distribution reservoir  20  corresponds to an input pressure of melt entering the casting apparatus  25 . This is because a level of the melt  15  in the distribution reservoir  20  corresponds to a metal input pressure of the casting apparatus  25  and the metal input pressure has been found to have an influence on the casting process and the obtained products. 
     Melt  15  may be supplied from the supply reservoir  10  to the distribution reservoir  20  via a supply conduit  30 . During casting, the supply reservoir  10 , the distribution reservoir  20  and the supply conduit  30  form a (supply) siphon. That is, during casting, an inlet  31  of the supply conduit  30  is submerged in melt  15  in the supply reservoir  10  and an outlet  32  of the supply conduit  30  is submerged in melt  15  in the distribution reservoir  20 . 
     In other words, at least during a steady-state casting operation, the casting equipment  1  is configured such that the supply conduit  30  defines a flow path that has a point a 1  that is higher than a surface of the melt in the supply reservoir  10  (c.f. metal level h 1 ) and/or the distribution reservoir  20  (c.f. metal level h 3 ), and a pump  35  is operated such that the metal level (h 3 ) in the distribution reservoir  20  is at an intended level such as to control a metal input pressure of the casting apparatus  25 . 
     The supply reservoir  10  and the distribution reservoir  20  may be separate reservoirs. A bypass valve, e.g. a dam valve,  11  may be provided to provide an optional direct fluid connection between the supply reservoir  10  and the distribution reservoir  20  that bypasses the supply conduit  30 . However, the supply reservoir  10  and the distribution reservoir  20  may also be physically separate from each other and there may be no other fluid connection between them than the supply conduit  30 . 
     An electromagnetic pump  35  is provided on the supply conduit  30  such as to generate a force/pressure in the melt  15  flowing through the supply conduit  30 . In  FIG.  1   , the pressure/force generated by the pump  35  is indicated by the letter “F”. The pump  35  may for example be provided on the supply conduit neighboring the inlet  31  or the outlet  32 . 
     During casting, a flow of the melt  15  from the supply reservoir  10  to the distribution reservoir  20  via the supply conduit  30  may be controlled by the pump  35  such as to control the metal level h 3  in the distribution reservoir  20 . 
     The supply conduit  30  may optionally be configured to be evacuated to generate an, with respect to the atmosphere surrounding the casting equipment  1 , under pressure therein. In  FIG.  1   , the under-pressure is indicated by the “P-” symbol. By controlling the underpressure in the supply conduit  30  and the electromagnetic pump  35  at the same time, the flow of melt  15  through the supply conduit  30  and consequently the melt level h 3  in the distribution reservoir  20  may be controlled more precisely during a casting operation. 
     A vacuum port  33  may be provided on the supply conduit  30  to generate an underpressure with respect to the atmosphere in the supply conduit  30 . A vacuum pump or other means for generating an under-pressure may be connected with the vacuum port  33  to lower a pressure in the supply conduit  30 . For example, a vacuum pump based on the Venturi principle may be used to generate the under-pressure. 
     Priming the supply conduit  30 , that is initially filling it with melt  15 , may be achieved by the pump  35  if the pump is submerged in melt  15 , e.g. when it is provided on side of the inlet  31  of the supply conduit  30 . If the pump  35  is not submerged in melt  15 , on a clean start of the casting equipment  1 , the pump  35  may not be sufficient to prime the supply conduit  30 , as it may not be able to efficiently generate a pressure in air. In this case, the supply conduit  30  can be primed by blocking the outlet  32  of the supply conduit  30 , e.g. with a valve or a lid, and by applying an under-pressure on the vacuum port  33  so that melt  15  is transported from the supply reservoir  10  into the supply conduit  30 . When the melt  15  reaches the pump  35 , the pump  35  can be operated to transport the melt  15  into the distribution reservoir  20 . 
     During casting, the pump  35  is operated to keep the metal level h 3  in the distribution reservoir  20  at an intended level while melt  15  is consumed by the casting apparatus  25  to produce cast products. The casting equipment  1  may comprise one or more level sensors  40 . A closed-loop control for the pump  35  may be implemented by providing a level sensor  40  to measure the level of melt  15 . The level sensor  40  may be configured to measure a distance of the surface of the melt  15  from the sensor  40  e.g. by using a laser, RADAR radiation, acoustic waves, an inductive sensor or a capacitive sensor or the like, and to output a corresponding level signal. Via the distance, a level h 1 , h 3  of the melt  15  can be calculated. 
     The level signal may be used to control the pump  35  such that the metal level remains at an intended value (SET VALUE), e.g. via a PID control algorithm or the like. The level sensor  40  may be provided such as to measure a melt level h 1 , h 3  in the distribution reservoir  20  or in the supply reservoir  10 . A more precise control can be achieved by providing at least two level sensors  40  to measure the melt levels in the distribution reservoir  20  and in the supply reservoir  10 . While a control based on the metal level h 3  in the distribution reservoir  20  has been described, due to the principle of conservation of mass and because the melt  15  does not undergo a significant change of specific volume in the casting equipment  1 , the control of the metal level h 3  may also be achieved by measuring a different metal level, e.g. a metal level h 1  in the supply reservoir  10  or a metal level inside the casting apparatus  25  (not shown), and by controlling the pump  35  based on that measured metal level. 
     To control operation of the casting equipment  1 , in particular operation of the electromagnetic pump  35 , and, if provided in the embodiment, control of the pressure in the supply conduit  30  and/or the distribution conduit  70  ( FIG.  3   ) as described further below, a controller, such as an electronic control unit (ECU), a computer or a distributed electronic control unit, may be operationally connected to the level sensor(s)  40 , the electromagnetic pump  35  and/or the pressure sources connected with the vacuum ports  33  and/or  73  to control an operation of the casting equipment  1 . 
     In embodiments of the invention that utilize an under-pressure in the supply conduit  30 , a level sensor  40  may be provided to measure the level of melt  15  in the supply conduit  30  to enable a precise control of flow of melt  15 . In addition or alternatively, in order to provide more precise control of the flow of melt  15 , in embodiments of the invention that utilize an under-pressure in the supply conduit  30 , a level sensor  40  may be provided on that side of the supply conduit  30  that is opposite to the side on which the pump  35  is provided. If for example the pump  35  is provided on a side of the inlet  31  of the supply conduit  30 , a level sensor  40  may be provided to measure a level h 3  of melt  15  in the distribution reservoir  20 . 
     On the other hand, if for example the pump  35  is provided on a side of the outlet  32  of the supply conduit  30 , a level sensor  40  may be provided to measure a level h 1  of melt  15  in the supply reservoir  10 . 
     According to the present invention and with reference to  FIG.  2   , the casting equipment  1  may be operated such that a metal level h 1  in the supply reservoir  10  is higher than a metal level h 3  in the distribution reservoir  20 . In this case, due to the supply siphon arrangement formed by the supply conduit  30 , the distribution reservoir  20  and the supply reservoir  10 , the electromagnetic pump  35  is operated to counter the gravity-induced flow of the melt  15  from the supply reservoir  10  towards the distribution reservoir  20 . That is, the pump  35  may be operated as a valve to control/counter/limit the gravity-induced flow of the melt from the supply reservoir  10  to the distribution reservoir  20 . In  FIG.  2   , this is indicated by an arrow showing the operating direction of the pump  35 . 
     According to the present invention and with reference to  FIG.  1   , the casting equipment  1  may also be operated such that a metal level h 1  in the supply reservoir  10  is lower than a metal level h 3  in the distribution reservoir  20 . In this case, the electromagnetic pump  35  is operated to transport the melt  15  from the supply reservoir  10  towards the distribution reservoir  20  against the natural pressure gradient. In  FIG.  1   , this is schematically shown by the arrow indicating an operating direction of the pump  35 . 
     The casting equipment  1  may optionally further comprise a shut-off valve  50 . The shut-off valve  50  may be provided in the flow path between the distribution reservoir  30  and the casting apparatus  25 . The shut-off valve  50  may for example be implemented as a dam or gate valve and may be used to interrupt the flow of melt  15  from the distribution reservoir  20  to the casting apparatus  25 , for example during start-up of the casting equipment  1  to enable a controlled initial filling of the casting apparatus  25 . 
     For example, the shut-off valve  50  may be closed until the metal level h 3  in the distribution reservoir  20  has reached an intended level and may then be opened so that melt  15  can flow into the casting apparatus  25 . 
       FIG.  3    shows a further embodiment of a casting equipment  1  according to the invention. 
     According to the embodiment shown in  FIG.  3   , the casting apparatus  25  is implemented as a DC (“direct chill) casting apparatus  60 . The DC casting apparatus  60  comprises a casting mold  65 , a distribution conduit  70  and a starter block  75 . The distribution conduit  70  is fluidly connected with the distribution reservoir  30  and the casting mold  65  to transfer melt  15  from the distribution reservoir  20  into the casting mold  65  via an upper opening of the casting mold  65 . Accordingly, in the embodiment shown in  FIG.  3   , the inlet of the casting apparatus  25  is connected to the distribution conduit  70 . The melt  15  at least partially solidifies in the casting mold  65  (by heat transfer from the melt  15  to the casting mold  65  and/or the surroundings) and exits the casting mold  65  via a bottom opening as a cast product  80 . The cast product  80  is supported by the starter block  75  that is vertically moveable with respect to the casting mold  65 . Accordingly, a cast product  80  is produced while melt  15  is supplied into the casting mold  65  and the starter block  75  is continuously moved vertically downwards. During this operation, a quasi-stationary flow and pressure condition (steady-state casting) is reached. In this manner, a cast product  80 , such as an extrusion ingot or a rolling slab or other longitudinal cast product, may be produced. 
     According to embodiments of the invention, the distribution conduit  70  and the casting mold  65  may optionally be sealed or sealable from the atmosphere. The distribution conduit  70  and the casting mold  65  may form a (distribution) siphon arrangement. 
     In other words, at least during a steady-state casting operation, the casting equipment  1  may be configured such that the distribution conduit  70  defines a flow path that has a point a 2  that is higher than a surface of the melt (c.f. metal level h 4 ) in the casting mold  65  and the surface of the melt  15  in the distribution reservoir  20 , wherein at least the distribution conduit  70  is sealed or sealable from the pressure of the atmosphere, wherein the distribution reservoir  20 , the distribution conduit  70  and the at least one casting mold ( 65 ) form a distribution siphon such that a metallostatic pressure of a surface of the melt  15  in the distribution reservoir  20  is equal to the metallostatic pressure of the surface of the melt  15  in the mold  65 . 
     Accordingly, during casting, the level (or in other words the pressure) of the melt in the casting mold  65  may be adjusted by adjusting the level (or in other words the pressure) of the melt  15  in the distribution reservoir  20 . 
     The distribution conduit  70  may optionally be configured to be evacuated to generate an, with respect to the atmosphere surrounding the casting equipment  1 , under pressure therein. In  FIG.  3   , the under-pressure is indicated by the “P-” symbol. By controlling the under-pressure in the distribution conduit  70 , the flow of melt  15  through the distribution conduit  70  and consequently the melt level in the casting mold  65  may be controlled more precisely during a casting operation, resulting in a higher quality of the cast product  80 . The distribution conduit  70  may be provided with a vacuum port  73 . Via the vacuum port  73 , an under-pressure may be generated in the distribution conduit  70 . A vacuum pump or other means for generating an under-pressure may be connected with the vacuum port  73  to lower a pressure in the distribution conduit  70 . For example, a vacuum pump based on the Venturi principle may be used to generate the under-pressure. 
     Priming the distribution conduit  70 , that is initially filling it with melt  15 , by applying an under-pressure on the vacuum port  73  so that melt  15  is transported from the distribution reservoir  20  into the distribution conduit  70 . Then, according to the siphon principle, melt  15  will automatically flow from the distribution reservoir  20  into the casting mold  65  via distribution conduit  70  when melt  15  is consumed by the casting process. 
     By this arrangement, a steady and precisely controllable flow of melt  15  from the supply reservoir  10  to the distribution reservoir  20  via the supply conduit  30  (supply siphon) and from the distribution reservoir  20  to the casting mold  65  via the distribution conduit  70  (distribution siphon) may be achieved.