EP3993921B1 - Melt supply for strip casting systems - Google Patents

Description

The invention relates to a strip casting plant comprising at least one casting furnace and at least one rotating mold with a casting gap, in particular a pair of rollers, rolls, caterpillars or strips. The invention further relates to a method for feeding an aluminum or aluminum alloy melt to the casting gap in a strip casting plant.

Strip casting using strip casting systems is an economical and energy-efficient alternative to the conventional production of metal strips via ingot casting, reheating and hot rolling. In strip casting, a hot strip is produced close to the final dimension directly from a molten metal. For this purpose, the molten metal is cast in a strip casting system in which the casting area or solidification area in which the cast strip is formed is delimited on at least one long side by a barrier that is continuously moved and cooled during the casting process. This barrier moves along with the solidifying strip, so that a so-called traveling mold is provided. Traveling molds allow a high casting and solidification speed. In industrial production, there are a large number of designs of such traveling molds, for example casting wheel processes or single-roll processes. Due to the required widths of metal strips and further efficiency improvements, processes with two cooled traveling barriers arranged opposite one another, between which a casting gap is formed, have become established, particularly in the field of aluminum or steel strip casting. In particular, casting rolling using a two-roll process (twin roll casting) in a horizontal or tilted direction has become established in the aluminium industry, while the vertical process is also used in the steel industry. In this process, the molten metal is poured into an internally cooled The metal is introduced into a pair of rollers and solidifies in the casting gap between the two rollers, then it is formed, drawn off as a strip and wound up, for example. On the other hand, the mostly horizontally operated two-chain process (twin belt casting or Hazelett process) has become established, in which the travelling mold is formed by opposite sides of two cooled (insulating block) chains, between which a casting gap is formed in which the molten metal solidifies. In addition, travelling molds in the form of caterpillar molds (block casting) are also used, in which cooling blocks, usually made of copper, are arranged on chain segments. These are usually tilted slightly against the horizontal.

The problem with the known strip casting processes is that a variable solidification front can arise across the width of the strip produced, which can lead to non-uniform product properties. For example, surface defects, segregation of alloy elements or a non-uniform grain structure can arise. Locally unsolidified molten metal can even get through the casting gap and cause the strip to break and thus the process to be terminated. These problematic effects become more critical with larger strip widths, which are particularly relevant for high process efficiency. For all strip casting processes, the uniform supply of the melt into the casting gap or the solidification zone of the rotating mold is therefore very important. Conventionally, the molten metal, which is usually fed via an open channel system from a higher-lying casting furnace, is therefore calmed down in an open tundish (intermediate vessel) before the casting gap. The molten metal is first collected in the tundish and then fed from the tundish to the casting gap by gravity. At the same time, the level of the melt pool in the casting area in front of the mold can be regulated via the tundish, for example by means of a plug provided in the bottom of the tundish.

Such a strip casting plant for carrying out a vertical two-roll process is known, for example, from WO 2004-000487 known. For a horizontal Process with travelling mould, such a strip casting plant with tundish is in the EP 0 433 204 A1 described.

From the JP 2016 147298 A and the US 2011/033332 A1 Strip casting plants for magnesium with feeding without tundish are known.

The disadvantage of these known processes, however, is that, on the one hand, the control of the supply of molten metal to the casting gap is difficult to control and not very dynamic. On the other hand, if the system fails, molten metal continues to flow towards the casting gap due to gravity, which can cause safety problems. The molten metal also tends to oxidize. Aluminum melt in particular oxidizes very quickly on the surface when it comes into contact with oxygen, especially at the high temperatures required by the process, and forms a relatively stable oxide layer. In the conventional process, the molten metal can therefore form such an oxide layer in the tundish. However, due to the unsteady guidance required by the process, this can repeatedly break up, so that oxides or other contaminants that settle on the oxide layer are mixed into the molten metal by turbulence. However, this leads to non-metallic inclusions in the metal strip produced in the form of oxide agglomerates with other alloying elements such as Mg, Si or Cr. These inclusions significantly deteriorate the quality of the strip and lead, for example, to impaired formability. To avoid this, it is known to shield the molten metal using the costly use of inert gas to protect it from oxidation.

The present invention therefore has the object of providing a strip casting plant which, on the one hand, enables improved control of the volume flow of the aluminum or aluminum alloy melt to the casting gap, improved productivity and improved strip quality and, at the same time, allows for increased safety. In addition, a corresponding method is to be proposed.

The subject matter of the present application is defined by the independent claims. The dependent claims describe preferred embodiments.

According to a first teaching, this object is achieved in a strip casting plant according to the invention in that the strip casting plant has at least one active means for transporting molten metal from the casting furnace to the casting gap.

In contrast to passive means, e.g. passive means that use only gravity, an active means for transporting molten metal from the casting furnace to the casting gap is understood to be a means that is designed to use energy to transport the molten metal so that the transport of the molten metal can be controlled via the active means. The active means for transporting molten metal can transfer energy to the molten metal mechanically, electrically or electromagnetically, for example. For example, the drive work of the pump can be converted into kinetic energy of the molten metal by means of a pump, or energy can be transferred to the molten metal by applying pressure and converted into kinetic energy of the molten metal. Active means for transporting molten metal are suitable, for example, for moving the molten metal at least partially against the direction of gravity.

Whenever reference is made to molten metal in the preceding or following, this refers to an aluminium or aluminium alloy melt.

It was recognized that by using active means to transport molten metal, the volume flow of the molten metal to the casting gap can be controlled very precisely and directly. With conventional feed systems, which feed molten metal to the casting gap passively by means of gravity, only indirect control is possible. The reaction times are therefore shorter with passive means, for example, a tundish with a feed is too long to enable real control in a fast-running process. In particular, the conventional intermediate storage of the molten metal in a tundish ensures that, for example, changes in the fill level of the melt pool in front of the casting gap can only be responded to with a certain time delay. If, on the other hand, the molten metal is actively transported according to the invention, for example by overpressure against gravity, the volume flow of the molten metal can be controlled very precisely. This means that the molten metal can be fed into a controlled, continuous solidification process. The molten metal can be fed very smoothly and in a controlled manner, in particular the breaking up of an oxide layer in the feeding process and thus the introduction of impurities into the melt can be avoided. The costly use of inert gas to prevent the formation of an oxide layer can therefore be dispensed with. Although a tundish can be provided, a tundish, which is generally provided in conventional melt feeding to calm the molten metal, can preferably be dispensed with. In addition, the productivity of the strip casting plant according to the invention can be increased compared to a conventional strip casting plant, since the strip speed is usually set as slow as the hottest point in the strip allows for safety reasons.

The strip casting plant according to the invention thus allows the production of a high-quality aluminum alloy strip close to the final dimension. The active means for transporting the molten metal can also improve the safety of operating the strip casting plant.

The travelling mould of the strip casting plant according to the invention can, for example, be a travelling mould of one of the conventional processes described at the beginning. According to the invention, the travelling mould is thus a pair of rollers, rollers, tracks or belts. For example, a pair of rollers arranged parallel to one another on the axis of a vertical twin roll caster, a pair of rollers arranged parallel to one another on the axis of arranged pair of rollers of a horizontal or tilted twin roll caster, two casting chains rotating one above the other (e.g. Hazelett) or caterpillar molds, which are held by a machine frame or arranged in a housing. The rotating mold has a casting gap as described above. The casting gap can, for example, be up to 2.5 m wide, so that particularly wide metal strips over 1.6 m wide can be produced; the possible strip width can therefore be close to one roll width, for example around 2.5 m. The casting gap can, for example, be 1 to 6 mm high, so that metal strips of a corresponding thickness can be produced. In addition, it is advantageous if the molten metal is cooled in contact with the rotating mold at a cooling rate of in particular at least 20 K/s, preferably 50 K/s. By using active means for transporting molten metal and in particular the precise control of the supply of molten metal that this enables, significantly higher cooling rates can be set, particularly preferably a cooling rate of at least 100 K/s and/or up to 8000 K/s. The high solidification rate can further reduce segregation processes that have a detrimental effect on the material properties. The strip speeds at which the cast metal strip emerges from the casting gap can be set in the range of 0.06 to 3.0 m/s.

The metal strip can then be wound up in a coil, for example, and fed to a subsequent cold rolling process on a cold rolling stand, or it can be hot and/or cold rolled in-line without intermediate winding. The metal strip can also be aged between strip casting and cold rolling.

The casting furnace can be designed as a container for the temporary storage of molten metal or the casting furnace can be designed as a melting furnace for melting molten metal. In particular, the casting furnace can be heated and/or controlled.

In a further embodiment of the strip casting plant, the at least one active means for transporting molten metal comprises a means for pressurizing and/or a means for pumping the molten metal.

A means for applying pressure is understood to mean a means that is designed to apply pressure to the molten metal in order to transport the molten metal from the casting furnace to the casting gap. For example, the surface of a molten metal pool in a storage facility for molten metal, for example in the form of a pressure chamber, can be subjected to pressure. A means for applying pressure can therefore comprise a pressure chamber, for example. A pressure chamber is in particular a preheated or heatable closed, i.e. pressure-tight chamber in which molten metal can be provided and subjected to pressure. In particular, the pressure chamber can be provided by a low-pressure furnace in which the molten metal can be heated and pressed into a riser pipe, for example by applying pressure. This design enables a particularly smooth and gentle melt flow and a simple control of the volume flow of the molten metal, for example via the set overpressure on the surface of the molten metal pool.

Alternatively or additionally, a means for pumping the molten metal can be provided. For this purpose, a means for pumping the molten metal can comprise, for example, a metal pump. A metal pump can transport the molten metal mechanically, for example by means of a screw. Preferably, an electromagnetic metal pump is used in order to transport the molten metal as quietly and evenly as possible.

If the strip casting plant fails, for example due to a power failure, no further molten metal is pumped and run-on can also be avoided.

According to a further embodiment of the strip casting plant, the at least one active means for transporting molten metal comprises a pressure furnace, in particular a low-pressure furnace.

A pressure furnace is in particular a closed furnace that provides a heatable chamber that can be pressurized. If the chamber is pressurized with low pressure, it is a low-pressure furnace. The use of low pressure enables the molten metal to be guided and regulated safely and smoothly. A low-pressure furnace is designed, for example, to allow a pressurization of 0.1 to 1.0 bar. Preferably a pressurization of 0.3 to 0.6 bar for the smoothest possible transport of the molten metal or 0.5 to 1.0 bar for a faster supply of the molten metal to the casting gap.

For example, commercially available low-pressure furnaces used for low-pressure die casting or appropriately scaled versions thereof can advantageously be used.

If the pressure or low-pressure furnace also has a riser pipe, a particularly safe strip casting system is provided because the molten metal can automatically sink back into the pressure chamber through the riser pipe if the pressurization fails.

The casting furnace can be designed separately from the active means for transporting molten metal. However, a particularly simple and economical strip casting system is obtained if, according to a subsequent design of the strip casting system, the casting furnace is designed as a low-pressure furnace. Further active means for transporting the molten metal can then be dispensed with, for example. The simpler design also enables simplified and therefore improved control of the volume flow and increased safety of the strip casting system.

In a further embodiment of the strip casting plant, the strip casting plant is a vertical strip casting plant. It has been found that the supply of molten metal to the casting gap provided according to the invention can be used particularly advantageously for vertically aligned strip casting plants in which a casting area or casting gusset is arranged above the casting gap. In vertical strip casting plants in particular, the conventional supply of molten metal from above to the casting gap leads to the uncontrolled formation of oxides in the upstream tundish, which can enter the casting gap uncontrolled via the outlet from the tundish. Even if the outlet of the tundish were conceivably designed as an immersion pipe with one end below the bath level of the melt pool, turbulence could still occur so that the oxides are not discharged from the tundish in a controlled manner. This is a problem in particular for aluminum melts, but can be avoided in a vertical strip casting plant with the guidance of the molten metal as suggested above.

In a further embodiment of the strip casting plant, the strip casting plant has means for regulating the volume flow of the molten metal to the casting gap and/or the height of the melt level in the casting gap.

It was recognized that the supply of the molten metal via active means for transporting the molten metal can be used advantageously to enable precise and rapid control of the volume flow of the molten metal to the casting gap. If the molten metal is moved against gravity by applying pressure, for example, the volume flow can be controlled very precisely. The volume flow of the molten metal can then be set and controlled very precisely by measuring the pressure and regulating the pressure accordingly. For example, a control circuit can have a computer that is set up to regulate the pressure for optimal operation, for example according to a known or determined correlation of pressure and required volume flow for a strip casting speed to be achieved. For example, pressure sensors can be provided to measure the pressure in a pressure chamber or a low-pressure furnace. It is also possible to control the volume flow by measuring the fill level of the molten metal, for example in the casting area or casting gusset. For example, both the fill level of the molten metal in the casting area or casting gusset and the pressure in a pressure chamber can be measured. A fast, closed control loop can be set up using such a combined measurement. For example, the casting area or casting gusset can have at least one fill level sensor and a low-pressure furnace can have at least one pressure sensor. In particular, existing pressure sensors can also be used, for example in low-pressure furnaces. The fill level or level of molten metal can be detected, for example, using non-contact eddy current distance sensors, induction probes, image-optical methods, contact probes or immersion sensors. The level is preferably determined using laser measurement, for example the casting area can have at least one laser distance sensor.

In contrast to conventional feed systems, where only indirect control is possible due to the supply of the casting gap via a tundish or very slow control is possible due to the long reaction times, active and fast control of the volume flow can be achieved. Since vertical strip casting processes in particular run very quickly, fast control is particularly important for these.

According to the invention, the strip casting plant has a casting area arranged in front of the casting gap.

The casting area is arranged in front of the moving mold and is limited by the moving mold. The casting area is, for example, a casting gusset and/or a distributor nozzle. The casting area can be designed as a casting gusset, whereby the casting area or the casting gusset is limited by the moving mold and at least one side dam is formed, preferably two side dams, which are arranged opposite each other on either side of the moving mold. In the casting area, a melt pool is formed during the production of a metal strip, from which molten metal flows or is drawn into the roll gap. In vertical strip casting systems, the casting area or casting gusset is arranged essentially above the casting gap and is limited by the upper area of the moving mold. In horizontal or tilted strip casting systems, the casting area is arranged to the side of and in particular slightly higher than the casting gap.

The pouring area or pouring gusset enables a particularly uniform distribution of the molten metal over the entire width of the rotating mold as well as the continuous supply of the molten metal to the pouring gap via the melt pool formed in the pouring area.

Particularly in horizontal or tilted strip casting systems, a distribution nozzle can also be provided, through which the molten metal can be fed to the casting gap and distributed over the entire width of the casting gap. The distribution nozzle is closed, for example, until just before the casting gap, so that the molten metal is only briefly exposed to the air or not at all. In this case, the casting area is essentially formed by the rotating mold and the ends of the distribution nozzle or only by the distribution nozzle, so that additional side dams can be completely or partially dispensed with.

According to the invention, the casting furnace is connected to the casting area by a pipe system. In particular, the casting furnace is connected to the casting gusset and/or the distributor nozzle by a pipe system.

In contrast to the conventionally used open channel system, the closed connection between the casting furnace and the casting area in the form of a pipe system ensures that the molten metal is guided to the casting area does not lead to uncontrolled oxidation of the surface of the molten metal. The pipe system also enables particularly smooth and controllable guidance of the molten metal from the casting furnace to the casting area. If the pipe system is also an essentially air-tight and/or gas-tight pipe system, uncontrolled oxidation of the molten metal can be avoided even better. In addition, by using closed pipes, molten metal can also be guided at least partially against gravity in a safety-related manner. The strip casting plant or the pipe system preferably comprises at least one heatable pipe and/or at least one ceramic pipe, particularly preferably at least one heatable ceramic pipe. Premature solidification of the molten metal can thus be avoided. Even more preferably, the pipe system only has heatable pipes, in particular heatable ceramic pipes.

According to the invention, the strip casting plant comprises means for feeding the molten metal into the casting area, via which the molten metal can be fed to the casting area below the surface of a melt pool formed in the casting area.

If the means for feeding the molten metal into the casting area are designed in such a way that the molten metal can be fed into the casting area below the surface of a melt pool, the surface of the melt pool can be kept even calmer. Breaking through the surface of the melt pool is avoided. On the one hand, this can prevent uncontrolled formation of oxides. On the other hand, uncontrolled mixing of oxides can also be effectively avoided because turbulence on the surface or movement of the surface can be avoided. This can prevent an oxide layer that has formed from being drawn in and mixed in in an uncontrolled manner.

In a further embodiment of the strip casting plant, the casting area has at least one side dam, wherein the at least one side dam has at least one feed opening for molten metal. In particular, the pouring area is a pouring gusset.

It has been shown that if the molten metal is fed into the melt pool via the side plate, disruptions and turbulences on the surface of the melt pool can be reduced or avoided. If the at least one feed opening is also advantageously arranged in such a way that it is below the surface of the melt pool formed in the casting nip during operation of the strip casting system, breaking through the surface of the melt pool, disruptions to the surface of the melt pool and turbulences can be particularly successfully avoided. This form of feed has proven to be particularly advantageous in vertical strip casting systems in particular.

In a further embodiment of the strip casting system, the casting area has at least two, preferably three feed openings for a metal melt. This makes it possible to achieve an even more uniform distribution of the metal melt in the casting area. In particular, the formation of a pronounced temperature gradient parallel to the casting gap can be avoided in a melt pool, so that a particularly uniform solidification of the metal melt in the casting gap can be achieved. In horizontal or tilted strip casting systems, the at least two, preferably three feed openings can preferably be arranged in the bottom of the casting area, so that the metal melt can be fed to the casting area from below, essentially against the direction of gravity. More preferably, the at least two feed openings are arranged essentially at opposite ends of the casting area in the width direction. A third feed opening is arranged, for example, centrally between two other feed openings.

This enables a particularly uniform feeding of the casting gap with molten metal and the provision of homogeneous isothermal molten metal at a constant speed at the casting gap.

The pouring area can also be pressurized with inert gas to prevent the formation of oxides on the surface of the melt pool.

According to a second teaching, the above-mentioned object is achieved in a method according to the invention for feeding a molten metal to the casting gap in a strip casting plant in that the molten metal is actively transported into the casting gap. If the molten metal is actively transported according to the invention, for example by overpressure against gravity, the volume flow of the molten metal can be regulated very precisely. This allows the molten metal to be fed into a controlled, continuous solidification process. The molten metal can in particular be fed very smoothly and in a controlled manner, in particular the breaking up of an oxide layer in the feeding process and thus the introduction of impurities into the melt can be avoided. The molten metal can for example be fed to the melt pool in such a way that the surface of the melt pool is not broken through or disturbed by bath movements.

In particular, the method can be carried out with a strip casting plant according to the invention.

In a further embodiment of the method, the at least one casting furnace is pressurized to transport the molten metal. For example, the surface of a melt pool in the casting furnace can be pressurized. The casting furnace is preferably a low-pressure furnace in which the molten metal is heated and pressed into a riser pipe, for example, by applying pressure. This embodiment enables particularly smooth and gentle melt flow and simple control of the volume flow of the molten metal, for example via the set overpressure.

In a further embodiment of the process, the molten metal is transported at least in sections against the direction of gravity. Guiding the molten metal at least in sections against the direction of gravity enables a particularly controllable and adjustable volume flow of the molten metal. In addition, if the system fails, the molten metal can fall back in the direction of gravity, for example into a riser pipe and/or a casting furnace, so that the molten metal can no longer flow and work safety can be increased.

If the molten metal is led from the casting furnace to the melt pool essentially in the absence of air and/or gas, uncontrolled oxidation of the molten metal can be avoided even better. For example, the strip casting system has a pouring gusset and/or a distributor nozzle arranged in front of the casting gap and the casting furnace is connected to the pouring gusset and/or the distributor nozzle by a pipe system, whereby the pipe system is or will be essentially completely filled with molten metal. Essentially completely refers here to the fact that unavoidable contamination may be present.

According to the invention, the molten metal is fed into the melt pool below the surface of the melt pool. For example, a melt pool is or will be formed in front of the casting gap and the molten metal is fed into this melt pool below the surface of the melt pool. This can prevent the surface of the melt pool from being broken through and/or swirled, which could lead to uncontrolled mixing of oxides into the molten metal.

Advantageously, the molten metal can also be fed into the melt pool from the side and/or from below. The molten metal is preferably fed into the melt pool or continuously fed into the casting gap, i.e. in particular without intermediate storage of molten metal in a tundish.

Fig. 1

eine schematische Schnittansicht eines Ausführungsbeispiels einer erfindungsgemäßen vertikalen Bandgussanlage,

Fig. 2

eine perspektivische Darstellung des Gießbereichs des Ausführungsbeispiels aus Fig. 1,

Fig. 3

eine schematische Schnittansicht eines weiteren Ausführungsbeispiels einer nicht erfindungsgemäßen horizontalen Bandgussanlage,

Fig. 4

eine schematische Schnittansicht eines weiteren Ausführungsbeispiels einer erfindungsgemäßen horizontalen Bandgussanlage und

Fig. 5

eine schematische Darstellung eines weiteren Ausführungsbeispiels einer erfindungsgemäßen horizontalen Bandgussanlage.

Further embodiments and advantages of the invention can be found in the following detailed description of some exemplary embodiments of the present invention, in particular in conjunction with the drawing. The drawing shows in

Fig.1

a schematic sectional view of an embodiment of a vertical strip casting plant according to the invention,

Fig.2

a perspective view of the casting area of the embodiment from Fig.1 ,

Fig.3

a schematic sectional view of a further embodiment of a horizontal strip casting plant not according to the invention,

Fig.4

a schematic sectional view of another embodiment of a horizontal strip casting plant according to the invention and

Fig.5

a schematic representation of a further embodiment of a horizontal strip casting plant according to the invention.

Fig.1 shows a strip casting plant 1 comprising a moving mold 2 with a casting gap 21, wherein the moving mold 2 is formed by two rollers 22, 23, and a casting furnace 3, wherein the strip casting plant 1 has an active means 4 for transporting molten metal 5 from the casting furnace 3 to the casting gap 21. The strip casting plant 1 here is a vertical strip casting plant 1. The active means 4 for transporting molten metal 5 in this example comprises a means 4 for pressurizing the molten metal 5 so that it can be actively transported from the casting furnace 3 to the casting gap 21 by the active means 4. In this example, the casting furnace 3 is designed as active means 4, in particular designed as a low-pressure furnace 4. The exemplary strip casting plant 1 has a casting area 6 arranged in front of the casting gap 21, which is designed as a casting gusset 6 and is arranged above the casting gap 21. The casting furnace 3, 4 is connected to the casting gusset 6 by a pipe system 42, 43, which comprises heatable ceramic pipes 42, 43. Furthermore, the casting gusset 6 has two side dams 62, wherein one side dam 62 has a feed opening 46 for the molten metal 5. The feed opening 46 is provided as a means 46 for feeding the molten metal 5 into the casting gusset 6, via which the molten metal 5 can be fed to the casting area 6 below the surface of the melt pool 52 formed in the casting area. The exemplary strip casting plant 1 thus comprises means 46 for feeding the molten metal 5 into the casting area 6, which can feed the molten metal 5 to the casting area 6 below the surface of a melt pool 52 formed in the casting area 6. The molten metal 5 here is, for example, an aluminum melt 5.

If the surface of the melt pool 53 in the low-pressure furnace 3, 4 is pressurized, for example via an air or gas supply 32, for example with 0.1 to 1.0 bar, preferably 0.5 and 0.6 bar, the molten metal 5 can be transported via the riser pipe 43 and the heated pipe 41 to the casting area 6 against the direction of gravity G. This enables a particularly quiet and gentle melt flow to the melt pool 52, without the surface of the melt pool 52 being broken or disturbed by movements of the surface or turbulence of the molten metal. Because the molten metal 5 is transported against gravity, the exemplary strip casting system 1 is designed to be very safe, since the molten metal 5 falls back into the low-pressure furnace 3, 4 in particular through the riser pipe 43 in the event of a system failure. In addition, a simple regulation of the volume flow of the molten metal to the casting gap is possible. For this purpose, the exemplary strip casting plant 1 has means for controlling the volume flow of the molten metal 5 into the casting gap 21 and/or the height of the melt level in the casting gap 21 in the form of a control loop. The control loop uses measured values from a fill level sensor 61, which measures the fill level or Level of the melt pool 52 in the casting area 6 and also to a pressure sensor 31, which measures the pressure in the low-pressure furnace 3,4. If, for example, a drop in the fill level of the melt pool 52 is detected by the fill level sensor 61, the pressure in the low-pressure furnace 3,4 can be increased in a controlled manner in order to adjust the fill level to an optimal fill level again. In contrast to the gravity-based conventional feed system, the exemplary strip casting system 1 can thus be actively and precisely controlled with fast response times.

Fig.2 shows in a perspective view the casting area 6 of the exemplary vertical strip casting plant 1 from Fig.1 The rotating mold 2 of the exemplary strip casting system 1 is formed by two rollers 22, 23. The casting area 6 is designed here as a casting gusset 6 and is formed by the rollers 22, 23 of the rotating mold 2 and two side dams 62. A side dam 62 has a feed opening 46 through which a metal melt 5 can be fed to the casting area 6 below the surface of a melt pool 52 formed in the casting area. In contrast to conventional methods that work with a dip tube made of a tundish located above the melt, the tundish can be dispensed with, which in turn leads to oxide formation and the negative effects described, such as uncontrolled oxide entry into the melt.

Fig.3 shows a strip casting plant 1 not according to the invention comprising a travelling mold 2 with a casting gap 21, wherein the travelling mold 2 is formed by two (insulating block) chains 25, 26, and a casting furnace 3, wherein the strip casting plant 1 has an active means 4 for transporting molten metal 5 from the casting furnace 3 to the casting gap 21. The strip casting plant 1 is here a horizontal or tilted strip casting plant 1. The active means 4 for transporting molten metal 5 comprises in this example a means 4 for pumping the molten metal 5 in the form of an electromagnetic metal pump 4, so that the Metal melt 5 can be transported from the casting furnace 3 from below into the distributor nozzle 63. The casting area 6 is formed, for example, by the closed distributor nozzle 63.

Fig.4 shows a further strip casting plant 1 according to the invention comprising a casting furnace 3 and a moving mold 2 with a casting gap 21, wherein the moving mold 2 is formed by two rollers 22, 23, wherein the strip casting plant 1 has an active means 4 for transporting molten metal 5 from the casting furnace 3 to the casting gap 21. The strip casting plant 1 here is a horizontal or tilted strip casting plant 1. The molten metal 5 is actively transported from below through the feed opening 46 into the casting area 6 via the metal pump 4. A melt pool 52 is formed in the casting area 6 here.

Fig.5 shows an exemplary strip casting system, wherein the casting area 6 has at least three feed openings 46 for molten metal. Two feed openings 46 are arranged in the width direction essentially at opposite ends of the casting area 6. A third feed opening 46 is arranged centrally between the two other feed openings 46. The molten metal 5 is actively transported from the casting furnace 3 via the metal pump 4 from below through the feed opening 46 into the casting area 6. As shown by way of example in Fig. 6, the feed from the furnace can be branched into several strands via the pipe 41 and fed through several pipes perpendicular thereto via several feed openings 46 to the casting area 6, in particular a casting gusset and/or a distributor nozzle, against the direction of gravity G. In this way, melt can be fed into the distributor system at several points at the same time, for example, at the same temperature and speed, thus ensuring that a homogeneous, isothermal melt flows across the entire width in the outlet into the casting gap 21.

The described embodiments of the strip casting plant 1 enable the uniform supply of aluminum melt 5 into casting areas 6 or to casting gaps 21, so that the casting and rolling processes are stabilized, productivity is improved and material defects can be avoided. This is achieved by feeding the molten metal 5 to the casting roll gap 21 below the surface of a molten metal pool 52, so that the surface of the existing molten metal pool 52 is not broken through or disturbed by bath movement. This avoids oxygen contact of the incoming molten metal 5 and thus reduces the total amount of oxides formed. Furthermore, there is then, for example, an intact, calm oxide layer 54 on the surface of the molten metal pool 52, which is not mixed into the molten metal and which protects the molten metal pool 52 from further oxidation. This makes it possible to avoid non-metallic inclusions in the strip produced.

This allows the strip casting system 1 to be operated at optimum speed without the risk of local melt breakouts. The strip quality can be kept consistent across the entire width. Uneven solidification across the width of the casting gap and, as a result, local melt breakouts through the casting gap, for example, can thus be avoided. This also prevents surface defects, cracks in the strip or casting breakages.

Furthermore, a melt introduced from below or from the side can be distributed in individual strands across the casting width, i.e. the width of the casting gap, so that a more homogeneous inflow with a uniform temperature and/or uniform speed to the casting gap can be achieved. This can improve the uniformity of the product properties across the width of the strip and the productivity of the system can be further increased because the risk of local melt breakthroughs is reduced.

The exemplary embodiments described can also be advantageous for reasons of occupational safety. If problems occur in the molten area of the system, the transport system can be switched off and the residual melt in the system immediately falls with gravity G through the riser pipe 42 into the furnace. There is no further flow of melt into the casting area.

Claims (11)

1. Strip casting system (1) for aluminium and/or aluminium alloys comprising at least one casting furnace (3) and at least one revolving chill mould (2, 22, 23, 25, 26) having a casting gap (21), wherein the at least one revolving chill mould (2, 22, 23, 25, 26) is designed as a roll pair (22, 23), roller pair, caterpillar pair or belt pair (25, 26), wherein the strip casting system (1) has at least one active means (4) for transporting aluminium or aluminium alloy melt (5) from the casting furnace (3) to the casting gap (21),
   wherein the strip casting system (1) has a casting region (6) arranged in front of the casting gap (21), wherein the casting region (6) is delimited on at least one side by the revolving chill mould (2, 22, 23, 25, 26) and the casting region (6) is designed in such manner that an aluminium or aluminium alloy melt pool (52) is formed in the casting region (6), from which aluminium or aluminium alloy melt (5) flows or is drawn into the casting gap (21), wherein the casting furnace (3) is connected to the casting region (6) by a pipe system (41, 42, 43), wherein the strip casting system (1) comprises means (46) for feeding the aluminium or aluminium alloy melt (5) into the casting region (6), which can feed the aluminium or aluminium alloy melt (5) to the casting region (6) below the surface of the aluminium or aluminium alloy melt pool (52) formed in the casting region (6).
2. Strip casting system (1) according to claim 1
   characterised in that
   the at least one active means (4) for transporting metal melt (5) comprises a means (4) for pressurising and/or a means (4) for pumping the metal melt.
3. Strip casting system (1) according to claim 1 or 2
   characterised in that
   the at least one active means (4) for transporting aluminium or aluminium alloy melt (5) comprises a pressure furnace (4), in particular a low-pressure furnace (4).
4. Strip casting system (1) according to any one of claims 1 to 3 characterised in that
   the casting furnace (3) is configured as a low-pressure furnace (4).
5. Strip casting system (1) according to any one of claims 1 to 4, characterised in that
   the strip casting system (1) is a vertical strip casting system (1).
6. Strip casting system (1) according to any one of claims 1 to 5, characterised in that
   the strip casting system (1) has means for regulating the volume flow of the aluminium or aluminium alloy melt to the casting gap (21) and/or the height of the melt level in the casting gap (21).
7. Strip casting system (1) according to any one of claims 1 to 6, characterised in that
   the casting region (6) has at least one side dam (62), wherein the at least one side dam (62) has at least one feed opening (46) for aluminium or aluminium alloy melt (5).
8. Strip casting system (1) according to any one of claims 1 to 7, characterised in that
   the casting region (6) has at least two, preferably three, feed openings (46) for aluminium or aluminium alloy melt (5).
9. Method for feeding an aluminium or aluminium alloy melt (5) to the casting gap (21) in a strip casting system (1) for aluminium and/or aluminium alloys comprising at least one casting furnace (3) and at least one revolving chill mould (2, 22, 23, 25, 26) designed as a roll pair (22, 23), roller pair, caterpillar pair or belt pair (25, 26) with a casting gap (21), in particular carried out with a strip casting system (1) according to any one of claims 1 to 8,
   wherein the aluminium or aluminium alloy melt (5) is actively transported into a casting region (6) arranged in front of the casting gap (21), wherein the casting region (6) is delimited on at least one side by the revolving chill mould (2, 22, 23, 25, 26) and the casting region (6) is designed in such manner that an aluminium or aluminium alloy melt pool (52) is formed in the casting region (6), from which aluminium or aluminium alloy melt (5) flows or is drawn into the casting gap (21), wherein the aluminium or aluminium alloy melt (5) is actively fed to the casting region (6) below the surface of the aluminium or aluminium alloy melt pool (52) formed in the casting region (6).
10. Method according to claim 9,
    characterized in that
    the at least one casting furnace (3) is pressurised to transport the aluminium or aluminium alloy melt (5).
11. Method according to claim 9 or 10,
    characterised in that
    the aluminium or aluminium alloy melt (5) is transported at least in sections against the direction of gravity (G).

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