WO2009092360A1 - Feeding device for a molten metal - Google Patents

Abstract

The invention relates to a strip casting device and a feeding device (1) for a molten metal, having a tipping crucible (2) receiving the molten metal and comprising an outlet opening. A floor surface (5) is formed opposite the outlet opening (4) by a convex recess (6) having a radius (R) corresponding to the distance of the pivot axis (3) from the floor surface (5). Because the outlet opening (4) matches the pivot axis (3) at least in segments, a constant change in angle of the tipping crucible (2) leads to a constant outlet velocity of the molten metal during the pivoting motion.

Description

 FEEDING DEVICE FOR A METAL MELT

The invention relates to a feeding device for a molten metal with a melt receiving, an outlet opening having crucible, which is designed as a pivotable about a particular horizontal pivot axis arranged tilting block and having an outlet opening opposite wall surface or bottom surface, which at least partially a convex shape with a Having the distance of the pivot axis of the wall surface and / or bottom surface corresponding radius.

In a process already known in practice, referred to as direct strip casting (DSC), which is currently the subject of development work, the liquid metal is poured by means of the feeder on a circulating from below water-cooled casting belt made of steel.

After the solidification of the metal layer, the 8-15 mm thick strip passes through a heat compensation / secondary cooling zone, so that then a multi-stage, for example three-stage inline hot rolling can be carried out at the temperatures which are suitable for adjusting material properties.

One of the key benefits of this strip casting technology is the lower investment and production costs that result from the compact system design combined with high productivity. In order to avoid oxidation of the hot metal, the entire area from the steel task to hot rolling is encapsulated, so that a protective gas atmosphere can be set.

The formation of the top surface of the cast strip depends significantly on the gas atmosphere set in the area of the casting machine.

DE 196 36 699 C2 describes a strip casting plant, in particular for the casting of metallic strips, which have a thickness of up to 10 mm. In a subsequent to the casting Anläge arrangement, a flexible support member is provided, which is particularly stretched between casting and a subsequent conveyor. The flexible support element absorbs the vertical forces caused by gravity.

A casting plant for the casting of particular molten steel is described in DE 34 23 834 C2. From a reservoir of liquid steel passes through a nozzle on an endless circulating, cooled and supported by rollers belt. The solidified strip is guided by conveyors of a subsequent plant for further processing, in particular rolling.

US Pat. No. 5,251,687 discloses a strip casting installation in which a flexible guiding and supporting element is arranged for the solidified strip. However, this is only for cooling and is thus not adjustable in its length and intended as a mass storage for the tape.

From document DE 32 27 132 A1 it is known to envelop a metal flow emerging from a metering nozzle in a protective casing of inert gas, for example argon or nitrogen, in order to keep air away from the vicinity of the molten metal. This pressurized inert gas shields the oxygen from the ambient air and thereby prevents reoxidation of the exposed molten metal miniscus.

When strip casting, as known from the document DE 38 10 302 A1, the liquid metal is placed on a cooled endless belt and the free surface of the belt strand cools during its transport on the conveyor belt, so that in the front area near the nozzle free Surface is highly liquid and then solidified by cooling. DE 10 201 592 A1 deals with the specific requirements for improving the required productivity and the thermal-mechanical processing in the production of magnesium-based high-purity flat products.

DE 41 16 998 A1 relates to a method for casting light metal parts of magnesium, in which the metal is melted under exclusion of air, conveyed into a mold and cured there. It is provided that the molten metal in Gießformunterteil, this upstream casting furnace and a separate melting furnace by siphon-like, each with their open ends projecting into the melt connecting lines tion at the same mirror level kept close to the mold inlet and by means of the casting furnace supplied overpressure under shut-off the smelting furnace line is conveyed into the lower casting mold and the actual casting mold. With such a method it is possible, after filling the casting mold, to keep the surface levels of the melt in the melting furnace, in the casting furnace and in the pouring tube below the casting mold at the same level, in each case just below the inlet into the casting mold, in order to ensure the respective shape Refill the mold to ensure the least possible movement of the molten material. Pouring furnace and casting mold can be connected via a pouring tube which opens out of the casting furnace and opens into the mold riser from below. Furthermore, the casting furnace may have a pressure feed line, in the pressurization of which the melt can be conveyed with the shut-off of the siphon line into the casting mold, wherein the inlet of the siphon line in the melting furnace can be shut off with a pressure-loaded valve. Because of the high tendency of the melt to oxidize, it is also expedient if the melt levels in the melting furnace and the casting furnace have a protective gas covering which consists of SF ₆ and / or CO ₂ .

The quality of the metal layer depends especially on the DCS process from the feeder. For example, such a feed device may have the shape of a groove. The flow of molten metal in the channel can be considered fluidically as a channel flow, so that the local flow velocity is influenced by the distance to the walls of the channel. The flow rate is further influenced by small bumps in the channel and by turbulence. These disturbances are further transmitted to the belt and thus the belt forming. For this reason, a homogeneous mass flow can not be achieved in practice, so that the strip thickness over the width of the metal layer also have an uneven distribution.

Furthermore, a feeding device known as the Single Beit Caster is already part of the state of the art. The melt is continuous by means of a Verdrängerstempels displaced from a crucible and poured in a constant flow of melt on a circulating, cooled from below casting tape. The displacer makes it possible to achieve a precisely defined metal mass flow. In particular, the volume displaced by the punch and fed to the casting belt depends linearly on the movement of the punch in the die, so that comparatively simple control of the mass flow by the punch movement can take place.

A disadvantage of this feeding proves to be the inhomogeneous temperature distribution on the displacer, which transfers to the melt. Furthermore, the method requires an energy-consuming heating of the displacer, which also causes a high maintenance effort. Furthermore, there is a high consumption of inert gas through the gassing of the punch and the leakage of the feeder. The process-related Schmelzerest that remains in the crucible, resulting in a considerable effort in the emptying and cleaning of the crucible after casting.

A large number of further proposals for achieving a constant mass flow have already become known from the state of the art. Thus, for example, the melt can be poured from a crucible into a container whose level is monitored, so as to regulate the further supply of melt through an actuator of the crucible.

Furthermore, a level control has already been proposed in which the casting speed between two distributors is controlled by measuring with load cells and calculating the necessary Kokillenbandgeschwindigkeit. In steady state operation, the level in the caster is measured and controlled by controlling the casting and drawing speed.

In addition, it has already been suggested to first fill the melt in an antechamber and then raise it by applying a negative pressure in a communicating with the first chamber second chamber. From this second chamber, the melt flows through a slanted nozzle on the casting belt. The pressure at the nozzle outlet results in this system from the height difference between the level of the casting belt and the filling level in the prechamber.

Generic casting devices with sections which are concentric with respect to the pivot axis are also known, for example, from DE 375332 C, DE 196 18 843 B4, DE 1 458 093 B, DE 742183 C and DE 480 831 C. Against this background, the invention is based on the object to provide a feeding device for a molten metal, through which a well-defined metal mass flow can be achieved with little effort. In particular, the control effort as well as the design effort for the preparation of the feeder and the maintenance and service costs should be substantially reduced. Furthermore, the invention is based on the object to provide an improved, equipped with such a feeder belt casting.

The first object is achieved with a feeding device according to the features of claim 1. The further embodiment of the feeding device can be found in the dependent claims 2 to 10.

According to the invention, therefore, a feed device is provided in which the outlet opening coincides, at least in sections, with the pivot axis. As a result, the melt volume flowing out in each case with an angle change of the tilting mirror can be determined in a simple manner and, with a low outlay on casting the melt, a mass flow or volume flow which is linearly dependent on the tilting angle of the tilting mirror, so that the control of the melt flow can be effected in a simple manner by the change the angular position of the tilting mirror can be done. The invention is based on the finding that with an increase in the pivoting angle, the corresponding outflowing melt volume likewise increases in the same way if the melt is delimited during the entire emptying of the tilting mirror by a wall surface or bottom surface which in cross-section is a circular sector equivalent. In this case, the center coincides with the pivot axis of the pivoting movement, which, of course, does not have to be embodied as a pivot axis that is inherently available. Two in the axial direction on both sides of the convex shape of the tilting mirror arranged wall surfaces are arranged in parallel, so as to ensure the linear discharge speed. Preferably, the entire bottom surface is formed by the convex shape.

A particularly advantageous embodiment of the feeding device is also achieved in that the molding is designed as a cutout or sector of a hollow cylinder. In particular, a simple tilting bolt can already be formed by such a section of the hollow cylinder.

A configuration which is particularly expedient in practice is achieved when the crucible has a basic shape with a bottom surface formed by the convex shape. has. As a result, the crucible is also suitable for use in devices known per se in connection with commercially available receptacles.

In principle, the outlet opening can be of any desired design and closable with a closing device, for example an automatically opening flap, wherein a lower outlet edge delimiting the outlet opening is arranged no higher than the plane defined by the pivot axis parallel to the liquid level with respect to the liquid level of the melt.

On the other hand, it is particularly useful if the crucible is gas-tight and closable. In particular, therefore, when casting the melt, only a single opening defined by the outlet opening relative to the environment is present.

Another likewise particularly promising modification is achieved when the crucible has at least one partition which divides the crucible volume into segments, from which the melt emerges as a separate melt flow, which is parallel with respect to the pivot axis. As a result, undesirable channel effects, ie a flow velocity reduced in the vicinity of the lateral wall surfaces, are compensated and thus deviating mass or volumetric flows are avoided. Furthermore, at least one partition can be used to fill several molds at the same time.

For this purpose, at least one partition is arranged in a plane perpendicular to the pivot axis, wherein the number of partitions, which may also differ from each other in terms of their shape, dimensions or orientation, to the respective requirements can be adjusted as needed. For this purpose, the partitions can also be arranged detachably or additionally also fixable in different positions in the crucible.

Another particularly practical embodiment, however, is achieved even if at least one partition wall is arranged in a plane perpendicular to the Seh wen k- axis inclined plane so as to realize a plurality of divergent melt streams in particular as mass flows, as for example in complicated Castings with multiple, different diameter channels may be required. At least one partition wall extends from the curvature to the outlet opening.

In another likewise particularly practical modification of the feed device according to the invention, at least one dividing wall is arranged such that in a rest position. tion, in which the liquid level of the melt is substantially below the outlet opening, an exchange of the melt between the segments is possible, while in a working position in which the liquid level of the melt reaches at least the outlet opening, an exchange of the melt between the segments is excluded.

As a result, the melt is distributed in the rest position by the unimpeded compensation automatically on all limited by the partition segments. As a result, for example, a further melt can be added and a homogeneous mixture produced by means of a stirrer. The replacement of the melt between the segments is thus prevented only during the casting.

For this purpose, the segments are preferably designed so that at least one partition is delimited by a spatial diagonal between the curvature and the wall surface having the outlet opening, wherein the partition at least slightly protrudes from the level of the pivot axis and also subdivides a drainage surface to the outlet edge.

The second-mentioned object of providing a strip casting device with a coolable casting belt, which is equipped with such a device and which operates according to the DCS method, is achieved in that the crucible is designed as a tilting crucible arranged pivotably about an in particular horizontal pivot axis and a wall surface lying opposite the outlet opening and / or bottom surface, which at least partially has a convex shape with a constant, the distance of the pivot axis of the wall surface and / or bottom surface corresponding radius. This belt casting device thereby enables a constant outflow speed of the melt with a constant angle change of the tilting mirror during the pivoting movement.

Furthermore, the tilting pot can be used in foundries. In order to ensure a good quality of the casting, each casting must be poured under defined conditions. These conditions include, among other things, the mold fill rate. The mold fill rate of each casting is independent of the casting size and can be controlled with the proposed tilting die. This ensures constant and stable casting conditions. The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in

1 shows a feeding device according to the invention with a tilting pot in a perspective view.

FIG. 2 shows a side view of the tilting bolt shown in FIG. 1 in a plurality of working positions pivoted about a pivot axis; FIG.

FIG. 3 shows a perspective view of the tilting mirror shown in FIG. 1 with four parallel partitions; FIG.

FIG. 4 is a side view of the tilting mirror shown in FIG. 3; FIG.

5 is a perspective view of the tilting mirror shown in Figure 1 with two mutually inclined partitions.

Fig. 6 in a side view of two basic forms of further embodiments of a tilting mirror.

A first feeder 1 according to the invention is shown in more detail with reference to Figures 1 and 2, which show a tilting pot 2 in a perspective view and in a side view in several working positions. The tilting block 2 has an angular basic shape and is pivotable about a horizontal pivot axis 3, wherein the pivot axis 3 at the same time limits an outlet opening 4. The outlet opening 4 opposite a bottom surface 5 is formed by a convex shape 6 with a radius R, which corresponds to the distance of the pivot axis 3 of the bottom surface 5. This construction of the tilting mirror 2 allows for a constant angular change of the tilting mirror 2, a constant outlet velocity of the melt during the pivoting movement. In particular, the radius R simultaneously determines the constant length of the liquid level 7 of the melt, as can be seen in particular in FIG. The tilting block 2 thus created is characterized by a simple design, high reliability and reliability and also offers the possibility of a gas-tight closability. Furthermore, the melt can be easily mixed. In addition, the tilting pot 2 can be completely emptied. The tilting crucible 2 thus created is dimensioned such that an angle change by 1 ° leads to a discharge of 0.4 l melt, whereby a volume flow is reached from 100 to 250 cm ³ / s at an angular velocity of the tilting mirror 2 between 0.2 and 0.7 7s.

A modification of the tilting mirror 2 is shown in a perspective view in FIGS. 3 and 4 and in a side view. The tilting pot 2 is equipped with four parallel partitions 8, which divide the crucible volume into five segments. All partitions are also arranged perpendicular to the pivot axis 3. In a rest position shown in Figure 4, the liquid level 7 of the melt is substantially below the outlet opening 4. An exchange of the melt between the segments is made possible in this position above the partitions 8 on the left side of the drawing. In a working position, not shown, during the outflow of the melt, the liquid level 7 of the melt reaches at least the outlet opening 4, wherein at the same time an exchange of the melt between the segments is excluded. Shortly before pouring the tilting pot 2 is tilted by a few degrees, so that the melt evenly between see the partition walls 8 distributed. During casting, the same amount of melt emerges from each segment. At the same time the possibility is created to stir the melt in the rest position or to move the melt in any other way.

Another possible use of the tilting mirror is shown in a perspective view with reference to FIG. The tilting block 2 is equipped with two mutually inclined partitions 8, 9, wherein the first partition wall 8 is arranged in a plane perpendicular to the pivot axis 3 and the second partition wall 9 is arranged in a plane perpendicular to the plane 3 inclined plane. As a result of this arrangement of the partitions 8, 9, it is possible to control two melt streams separately from each other, ie in particular to realize different volume flows. In this case, during casting from the first segment, a constant melt flow, while the speed of the emerging from the second segment melt flow increases linearly due to the inclination of the partition wall 9. Such requirements may arise with complicated castings which require casting through multiple channels of different cross-sectional area. Alternatively, if necessary, a targeted uneven distribution of the amounts of melt can be adjusted to realize targeted geometric variations across the width and - in the case of adjustable dividing walls 8, 9 - also the length.

FIG. 6 shows two further embodiments of a tilting seal 10 and of another tilting seal 11 with a bottom surface 5 which is extended beyond the pivot axis 3 in the direction of the left-hand side.

Claims

1. Feeding device (1) for a molten metal with a melt receiving, an outlet opening (4) having crucible, which is designed as a pivotable about a particular horizontal pivot axis (3) tilting crucible (2, 10, 11) and one of the outlet opening (4) has opposite wall surface and / or bottom surface (5) which at least partially has a convex shape (6) with a distance of the pivot axis of the wall surface and / or bottom surface (5) corresponding radius (R), characterized in that the outlet opening (4) at least partially coincides with the pivot axis (3). 2. Feeding device (1) according to claim 1, characterized in that the molding (6) is designed as a section of a hollow cylinder. 3. feeding device (1) according to claims 1 or 2, characterized in that the tilting pot (2, 10, 11) has a polygonal basic shape with a by the convex formation (6) formed bottom surface (5). 4. Feeding device (1) according to at least one of the preceding claims, characterized in that the tilting pot (2, 10, 11) is designed gas-tight closable. 5. Feeding device (1) according to at least one of the preceding claims, characterized in that the tilting pot (2) has at least one, the crucible volume into segments dividing partition (8, 9). 6. feeding device (1) according to claim 5, characterized in that at least one partition wall (8) is arranged in a plane perpendicular to the pivot axis (3). 7. feeding device (1) according to claim 5 or 6, characterized in that at least one partition wall (9) is arranged in a relation to the plane perpendicular to the pivot axis (3) inclined plane. 8. Feeding device (1) according to at least one of claims 5 to 7, characterized in that at least one dividing wall (8, 9) extends from the formation (6) to the outlet opening (4). 9. feeding device (1) according to at least one of claims 5 to 8, characterized in that at least one partition wall (8, 9) is arranged such that in a rest position in which the liquid level (7) of the melt substantially below the outlet opening ( 4), an exchange of the melt between the segments is possible, while in a working position in which the liquid level (7) of the melt reaches at least the outlet opening (4), an exchange of the melt between the segments is excluded. 10. Feeding device (1) according to at least one of claims 5 to 9, characterized in that at least one dividing wall (8, 9) by a spatial diagonal between the formation (6) and the outlet opening (4) having wall surface and / or bottom surface ( 5) is limited. 11. A with a feed device (1) according to at least one of the preceding claims equipped strip casting with a casting belt.