Continuous casting installation, tundish for continuous casting installations and continuous casting process

Abstract

The invention relates to a continuous casting installation for the continuous casting of metal, comprising at least a first metallurgical vessel (2) and a tundish (3) thereunder, wherein an inflow (4) with an outlet opening (32) for liquid metal is provided from the first metallurgical vessel (2) into the tundish (3) and the tundish has at least one outflow (15), which opens out into a casting mould (16), wherein the tundish (3) has at least two end walls (5, 6), at least two side walls (7, 8) and a base (9), characterized in that, to form a singular, helical rolling flow (22) of liquid metal from an inflow (4) to an outflow (15) during the continuous casting, one or more or all of the following measures are provided in the tundish: a) the inflow (4) from the metallurgical vessel (2) into the tundish (3) is offset from the centre axis (10) towards a side wall (7, 8) such that, during the continuous casting, a flow of the incoming liquid metal forms along a first side wall (8), then along the base (9) and on the opposite side wall (7) back again in the direction of a bath surface level (13); b) located below the inflow (4) there is a flow modifier (24), which either has at least one baffle area (25), arranged at an angle with respect to the vertical axis (23) and / or the centre axis (10), or is designed as a deflecting box (34) with an opening (35) in the direction of a side wall (7, 8), wherein the baffle area (25) or the deflecting box (34) is aligned such that, during the continuous casting, metal flowing out of the inlet (4) is deflected by the baffle area (25) or the opening (35) in the deflecting box (34) in the direction of an opposite side wall (7, 8) and a flow rising up to a bath surface level (13) forms on this wall; c) a gas-bubbling element (30) is provided on the base (9) in the region of a side wall (7, 8) and / or a gas-bubbling element (31) is provided in the region of the side wall (7, 8) in such a way that, during the continuous casting, gas passed through the gas-bubbling elements (30, 31) rises up to the bath surface level (13) and, by entraining liquid metal, forms a flow; d) the outlet opening (32) of the inflow (4) is only directed towards one of the side walls (7, 8), and the invention also relates to a tundish for this and to a continuous casting process.

Description

[0001] Voestalpine Steel GmbH

[0002] Continuous casting plant, distributor for continuous casting plants and continuous casting processes

[0003] The invention relates to a continuous casting plant, a distributor for continuous casting plants and a method for continuous casting.

[0004] Continuous steel casting is a well-known process for the continuous casting of steel slabs.

[0005] For this purpose, steel is usually produced in a converter, transferred from the steel converter to a ladle and from the ladle via a distributor to the casting mold.

[0006] The distributor's task is to ensure an uninterrupted flow of steel after one ladle has been emptied and the next ladle has been fed.

[0007] In principle, it must be ensured that there are no inclusions in the liquid steel, in particular no slag particles or components of the respective refractory lining or spraying of the vessels as well as reaction products from metallurgical treatment steps.

[0008] This is achieved in particular by arranging appropriate fittings in a distribution trough, which generates a certain upward flow after the steel has been filled in such a way that the steel is flushed to the surface, so that particles which are lighter than the steel are absorbed into the slag or are bound by the slag.

[0009] A continuous casting plant is known from DE 33 37 739 A1. This continuous casting plant has a ladle holding and changing device (ladle turret), ladles, a tundish, a continuous casting mold, and a strand withdrawal device. A tundish is assigned to the ladle, which is filled with molten metal and is in the preparation position for transport to the casting position, for joint transport with the ladle. In this embodiment, the tundish is preferably inserted into the arm provided for receiving the ladle on the ladle turret below the ladle. The tundish and / or ladle are provided with means for detachable connection to one another.

[0010] From EP 0 119 853 A2 a tundish for continuous casting is known, wherein the tundish has a channeled induction heating device arranged on the side wall of the tundish, wherein the device comprises a channel communicating with an opening in the side walls of the tundish.

[0011] EP 0 140 217 A1 discloses a method and a device for changing the casting ladle and the intermediate vessel in a continuous casting plant.

[0012] From EP 0 726 115 A1 a tundish for receiving and filtering ferrous metal melts is known, which tundish has a discharge opening in the bottom area for withdrawing the metal melt after passing through a deflection and / or filtering device, wherein a ceramic filter is arranged in the tundish, which essentially covers the entire horizontal cross section of the tundish and can be removed in a manner known per se, which filter extends essentially in a horizontal direction and is provided with passage openings which are arranged in the essentially vertical flow direction of the metal melt through the tundish, whereby cleaning or filtering of metal melts can be achieved with a simple construction even for high casting speeds.EP 0 804 306 B1 discloses a device for regulating the flow of molten metal in a tundish to improve the separation of inclusions from the metal bath. For this purpose, a flow control dam is positioned downstream of a shock buffer, which has an upper portion configured to receive a flow of molten steel detaching from the shock buffer and divert it into at least one secondary flow flowing in a downstream direction toward the slag blanket and at least one secondary flow flowing in an upstream direction toward the slag blanket. Ultimately, this is a built-in dam designed to prevent short-circuit flow.

[0013] US Pat. No. 6,074,600 discloses a modification of a tundish dam to minimize turbulence. This is intended to reduce the formation of gas bubbles and slag inclusions, particularly during the initial filling of the tundish. For this purpose, a type of weir is arranged between the steel inlet of the tundish and the steel outlet of the tundish. The weir extends from the bath surface to the bottom, but is spaced from the bottom. Furthermore, a ramp is arranged between the weir and the steel outlet, while a second ramp is arranged upstream of the weir.

[0014] To prevent whirlpools in vessels containing molten steel, DE 10 2009 009 740 A1 discloses vortex stones arranged in the area of ​​the bottom outlets so that their knife edges extend into the vortex. The vortex stones consist of a circular segment-like, flat fixing part and the braking part with the knife edge. This one-piece component can be practically placed on the bottom outlet, or better yet, placed on a perforated stone and connected to it, because the inner diameter corresponds to that of the bottom outlet. EP 3496882 B1 discloses a baffle plate for placement in a distributor to reduce the effects of misalignment of an impinging stream of molten steel entering the distributor.

[0015] It is also known to equip tundishes with a lowered floor from the steel inlet to the steel outlet. A dam or raised section is placed on this inclined floor, sometimes even a stepped floor, so that the steel inlet area forms a kind of pot, from which, after the pot is filled, the water flows over the dam and then fills the entire tundish. This dam also serves to ensure turbulent flow and slightly extend the residence time of the steel in the tundish, and in particular, to achieve contact with the slag layer.

[0016] From CN 103 25 465 Bl, a so-called turbulent flow controller for asymmetric use in the distributor is known, in which the shadow tube is arranged above this installation, whereby this installation is arranged in a plate-like manner with a slightly raised bottom on one side next to other shafts in the distributor.

[0017] A comparable installation is known from CN 102 000 791 A, which is located below the shroud and next to two ridges in the base of the distributor. However, the base of this installation, which has a cuboidal basic shape, is wave-shaped, with the steel from the shroud being cast into this structure and then emerging from it again above.

[0018] From KR 2003 00 52 756 A, an installation is known that is also arranged in a trough-shaped manner with its own vertical walls within the distributor. The shroud pipe terminates in a spring-like projection, and from there, the steel initially fills this trough-like structure before flowing into the rest of the distributor. The basic shape of the installation is somewhat T-shaped, with the steel flowing through a reduced opening into the rest of the T-shaped sub-distributor.

[0019] A comparable installation is known from EP 0 804 306 Bl, in which the steel is first filled into a trough located on the ground, then exits from the side and meets usual wall installations.

[0020] Such a trough-like installation is also known from CN 217 121 721 U, in which the trough is rather elongated-oval, but also with a wave-shaped bottom structure, so that the steel is first filled into this trough and then runs out of it into the rest of the distributor.

[0021] From "Numerical and Physical Study on New Simple Design of Subflux Flow Controller for One-Strand Tundish", Cwudziriski, Adam; Materials 2022, 15, 3756 ff., the influence on the flow using an asymmetric shadow tube was investigated, simulating various arrangements.

[0022] From "Physical and mathematical modeling of inclusion behavior in a tundish with gas curtain" Metallurgy and Materials 73(4), 531 - 538 2020, the influence of gas curtains in the inlet area was investigated, whereby the inlet area was additionally designed with walls hanging down from above and walls rising from below.

[0023] It was found that all these measures either calm the flow of the liquid melt, but then lead to a shorter residence time, or make it so turbulent that the particle load is high. The object of the invention is to create a continuous casting plant that leads to improved particle separation with minimal residence time and significantly improves the purity of the steel melt.

[0024] The problem is solved by a continuous casting plant having the features of claim 1.

[0025] Advantageous further training is indicated in subclaims.

[0026] A further task is to create a distributor for a continuous casting plant which leads to improved particle separation with minimal residence time and brings about a significant improvement in the purity of the molten steel.

[0027] The problem is solved with a distributor having the features of claim 17.

[0028] Advantageous further training is indicated in the dependent claims.

[0029] A further object is to create a continuous casting process which achieves improved particle separation with minimal residence time and a significant improvement in the degree of purity.

[0030] The problem is solved by a method having the features of claim 26.

[0031] Advantageous further training is identified in dependent subclaims.

[0032] It is a further object of the invention to provide a method for operating a distributor that improves particle separation. The inventors have recognized that by deliberately altering the flow conditions in the distributor, in particular the vortex structures, and increasing the residence time of the particles, particularly particles of non-metallic inclusions (NME), in the melt, the probability of separating the unwanted particles is increased.

[0033] From "Physical and numerical flow simulation of continuous casting processes in high-temperature technology," Jürgen Odenthal, ISBN 3-937057-10-2, 1st edition 2004, it is known that the distributor flow induced from the ladle via the shroud without any internals in the distributor very often moves in the form of two counter-rotating vortex formations or rolls towards the plug or the pouring tube and the mold, which can be seen particularly in the image on page 129 of this publication. These two counter-rotating vortex formations are also called "double rolls."

[0034] The inventors have also discovered that while the usual internals in tundishes may slightly increase the residence time and can also create arbitrarily complex flow patterns, they do not lead to successful separation of the unwanted particles. This may become even more important in the future, as steel production transitions from the traditional converter-based process of refining a mixture of scrap and pig iron and transferring this crude steel to a ladle, to electric steelmaking and upstream direct reduction. This process may result in a higher particle load.

[0035] The inventors have discovered that a singular helical flow or flow roller of the liquid metal in the tundish from the inlet, i.e., the shroud, to the outlet, i.e., the pouring plug, significantly reduces the number of inclusion frequencies per unit area in the cast slab. It is particularly advantageous if this flow extends over as much of the tundish cross-section as possible, i.e., starting from the inlet, over the shroud, over the tundish walls, extending to the bath surface, and then extending in a helical fashion forward to the outlet via the pouring tube. Preferably, at least 80%, preferably 90%, of the tundish cross-section should be encompassed by the singular flow roller.

[0036] According to the invention, this screw- or roller-shaped flow, which is referred to as single-roll, is generated by, for example, an asymmetric or eccentric positioning of the shadow tube in the XY plane of the distributor.

[0037] In general, the coordinate system is defined such that the Z-coordinate axis denotes a normal direction that is perpendicular to the surface of the distributor, the X-coordinate axis points in the direction of metal flow from the shadow tube (inlet) towards the outlet in the distributor and the Y-coordinate axis points in the transverse direction of the metal flow in the distributor towards the outlet.

[0038] In addition, the geometry of the flow modifier can be adjusted to influence the flow. This can be achieved through fittings such as a ramp or deflection boxes. The single-roll vortex structure is created by deflecting the flow asymmetrically toward one sidewall, rather than the usual symmetrical deflection toward both sidewalls or the endwall.

[0039] Furthermore, gas purging devices such as purging beams can be used to enhance the single-roll vortex structure. Furthermore, the geometry of the inlet, i.e., the shroud tube, can be adjusted to influence the flow.

[0040] Each of these measures can be carried out individually, several of these measures or all of these measures.

[0041] The asymmetric or eccentric positioning of the shroud in the XY plane of the tundish, or the correspondingly modified arrangement of the tundish beneath a ladle or other metallurgical vessel, results in the incoming steel hitting the bottom of the tundish and being naturally deflected upward by the opposite wall. In addition, the outflow through the pouring plug will lead to the formation of a helical single-roll flow structure.

[0042] By generally modifying the distributor base to a concave, curved shape, the cylindrical flow can be supported and dead corners avoided. The jet from the shroud tube can enter the distributor in the area where the concave base transitions into a side wall, thus being deflected.

[0043] The flow modifier according to the invention for influencing the flow can, for example, be a ramp that is formed in the distributor such that an inclined impingement surface of the ramp points towards the shroud tube, so that the liquid metal flowing into the distributor first encounters the impingement surface of this ramp and is deflected by this ramp according to the ramp gradient. However, it can also be a deflection box, i.e. a box-shaped device that is open at the top so that the flow from the shroud tube can flow in and has an opening towards a side wall, whereby the flow from the shroud tube can be deflected accordingly. The deflection box can also have several openings, but these must all be directed towards only one side wall in order to generate the single-roll flow according to the invention. The base of the deflection box can be flat or curved or can have grooves or other indentations.Furthermore, a nozzle-like impulse of the melt can also be provided within the deflection box, but in any case the steel melt should be deflected towards a side wall so that the liquid metal is deflected sideways and the roller flow is thereby generated.

[0044] In both variants, a corresponding upward deflection will occur on the side wall opposite the ramp with respect to the opening of the deflection box, resulting in the aforementioned single-roll flow structure. Of course, it is also possible to combine an asymmetric or eccentric positioning of the shadow tube with a corresponding ramp-shaped flow modifier, with the flow modifier then being arranged in the area of ​​the asymmetric-eccentric positioning or, for example, being formed by a side wall of the distributor in this area.

[0045] The impact surface can be inclined with respect to the xy direction, i.e. transversely to the width of the distributor. However, it can also have an inclination in the direction of the outlet or against the direction of the outlet. This is shown as an example in Figure 14, in which an angle beta (ß) is visibly shown. Preferably, an angle ß of -45° to 45°, preferably 0° to 45°, in particular 0° to 20°, preferably 0° to 10°, particularly preferably 1° to 5° in the direction of the x-axis, starting from the y-axis, can be set. This can influence the initial angle of the singular, screw-like flow roller and thus influence the residence time accordingly. In one embodiment, the angle can be set comparatively steeply, e.g. 35° to 45°, in order to be able to specifically control the mixing time when the quality changes in the distributor.Increasing the angle can improve the quality of the mixture when mixing liquid melts from electric furnaces with liquid melts from conventional blast furnaces. Furthermore, the inclination angle alpha (a), as shown by way of example in Figure 3, can be set to greater than 20°, preferably greater than 30°, particularly preferably greater than 40°, with respect to the y-axis in the z-axis direction in order to create an optimized deflection effect on the side wall. The angle alpha (o) can be selected to be less than 80°, preferably less than 70°, with respect to the y-axis in the z-axis direction in order to be able to generate a singular, helical flow roller with increased vortex intensity in the side wall.

[0046] In the case of a deflection box, adjustments to the opening angle are also conceivable, with an angle of -60° to 60°, preferably -45° to 45°, relative to the y-axis in the z-axis direction being conceivable, i.e., an upward-facing opening toward the bath level can also be provided. Additionally or alternatively, the opening can also have an angle of -45° to 45° in the x-axis direction, starting from the y-axis. This angle can also be achieved by offsetting the deflection box relative to the distributor.

[0047] Additionally, a channel flow can be introduced through a gutter, pipe, or similar device. This can also be achieved by adjusting the outlet of the shadow pipe.

[0048] In addition, the impact surface can be grooved or concave in shape rather than flat.

[0049] In addition to these two measures, the opposite wall of the distributor, which deflects the flow upwards towards the covering slag, can of course also be designed with a bevel or a ramp in order to enable the most complete flow possible without turbulence in a dead corner formed by the bottom wall and the side wall. Another possibility for creating a corresponding single-roll flow pattern is to blow gas in from below, particularly in the wall or adjacent to the wall, in particular at a distance of 200 mm from the wall which deflects the flow upwards, i.e. towards the covering slag. Gas purging of this type is also known, for example, from converters. Inert gases are particularly used as purge gas.

[0050] This gas causes the rising gas bubbles to intensify the existing flow and thus entrain the material, i.e., the liquid metal, thus promoting the single-roll flow pattern. Furthermore, these gas bubbles can also specifically influence the liquid steel flow, directing it to the covering slag, thus facilitating particle deposition in the slag.

[0051] The gas purging measure can, of course, be combined with the first-mentioned measure of asymmetrical-eccentric positioning of the shroud tube or adjusting the geometry of the flow modifier to create a ramp, or with both measures. It can also be used alone to create a single-roll vortex structure. Gas purging can take place over a partial length of the distributor, at specific points, or at multiple locations.

[0052] The gas can be blown in through the bottom of the distributor and the bottom surface of the distributor, as is also the case in the converter with so-called purging stones.

[0053] Furthermore, it is possible to inject the gas through so-called purge bars installed at the bottom of the distributor, which are located adjacent to the wall that directs the metal flow upwards. Such a purge bar can, of course, also have a ramp-like slope toward the flow or the center of the distributor, which additionally directs the flow upwards gently and without harsh transitions, and then further intensifies it with the injected gas.

[0054] If the gas is injected at such a high rate that the induced flow from the distributor base to the bath level is 5 to 15, in particular 10, times greater than the longitudinal flow of the metal from the inlet to the outlet, a roller-like singular flow can be generated solely by the gas purging. For example, the longitudinal flow in a conventional distributor can be approximately 20 mm / sec. If a gas flow of, for example, 50 to 100 operating liters per minute is introduced at a side wall or adjacent to a side wall, and the steel flow in this area can be, for example, 100 to 200 mm / sec, then such a strong superposition can be generated that the desired single-roll flow according to the invention can develop.

[0055] The invention thus relates to a continuous casting plant for continuous metal casting, comprising at least a first metallurgical vessel and a distributor arranged underneath, wherein an inlet or shadow tube with an outlet opening for liquid metal is arranged from the first metallurgical vessel into the distributor and the distributor has at least one outlet which opens into a casting mold, wherein the distributor has at least two end walls, at least two side walls and a base, wherein one, several or all of the following measures are provided in the distributor to form a singular, screw-like roller flow of liquid metal from an inlet to an outlet during continuous casting: a.the inlet from the metallurgical vessel into the distributor is offset from the central axis to a side wall, so that during continuous casting a flow of the incoming liquid metal develops along a first side wall, then along the bottom and along the opposite side wall again in the direction of a bath level; b. a flow modifier is arranged below the inlet, which either has at least one impact surface arranged obliquely with respect to the vertical axis and / or the central axis or is designed as a deflection box with an opening in the direction of a side wall, wherein the impact surface or the deflection box is aligned such that during continuous casting metal flowing out of the inlet is directed by the impact surface or the opening of the deflection box in the direction of an opposite side wall and a flow develops along this side wall up to a bath level; c.in the area of ​​a side wall, a gas purging element is arranged at the bottom and / or a gas purging element is arranged in the area of ​​the side wall in such a way that, during continuous casting, gas guided through the gas purging elements rises to the bath surface and forms a flow by entraining liquid metal; d. the outlet opening of the inlet is directed only in the direction of one of the side walls.

[0056] A further development provides for the impact surface of the flow modifier to be flat, convexly curved, or concavely curved and / or designed with a contour or recesses. This advantageously allows the angle of the induced single-roll flow or helical roller flow along the distributor axis to be easily and robustly adjusted.

[0057] A further development provides that the distributor is a longitudinal or transverse distributor or V-distributor. A further development provides that the outlet opening of the inlet is opened or shaped so as to be directed at an angle ß of -45° to 45°, preferably 0° to 45°, in particular 0° to 20°, preferably 0° to 10°, particularly preferably 1° to 5°, set to the y-axis in the direction of an outlet. Advantageously, the initial angle of the induced single roll flow can thus be adjusted so that the longest possible residence time can be induced at an angle ß of 0° to 20°, preferably 0° to 10°, particularly preferably 1° to 5°. At an angle ß of 30 to 45°, the rate of mixing of liquid melts from electric furnaces with melts from conventional blast furnaces can be increased. The mixing zone length can hereby advantageously be increased and the accompanying element level can thus be homogenized.

[0058] A further development provides that the distributor has one or more inlets.

[0059] A further development provides that the distributor has one or more outlets.

[0060] A further development provides that the at least one inlet from the metallurgical vessel is arranged adjacent to an end wall, and the at least one outlet is arranged adjacent to the opposite end wall. This can be advantageous for longitudinal distributors, as it allows for optimal yield or an increased residence time of the molten steel.

[0061] A further development provides that the distributor has several distributor fingers, each with at least one outlet.

[0062] A further development provides for the outlet(s) to be arranged at a distance of less than 200 mm, and preferably less than 100 mm, from the adjacent end wall. This comparatively close arrangement allows the dead volume to be further reduced.

[0063] A further development provides that the gas purging elements are designed as gas purging stones, gas purging bars or the like in the floor and / or the side wall or on the floor or a side wall.

[0064] A further development provides that the gas purging elements are designed to create a flow from the distributor base to the bath surface, which overlays the existing flow from the inlet to the outlet and is 5 to 15 times the flow velocity from the inlet to the outlet. Advantageously, the gas flow can be introduced at, for example, 50 to 100 operating liters per minute at a side wall or adjacent to a side wall. If the gas flow in this area can reach, for example, 100 to 200 mm / sec, such a strong overlay can be created that the desired single-roll flow according to the invention can develop.

[0065] A further development provides for the distributor base to be barrel-shaped and concave in order to support the single roll flow formation.

[0066] A further development provides for the edges between the distributor base and the side walls to be rounded or bridged with wedge-shaped elements. This advantageously allows the dead volume to be further reduced.

[0067] A further development provides that the side wall, to which the shroud tube is offset, is formed with a reinforced refractory support or a refractory plate in the inlet area. A further development provides that the outlet is offset from a side wall relative to the central axis of the distributor.

[0068] A further development provides that the outlet is offset in the same direction to the same side as the shadow tube.

[0069] A further aspect relates to a distributor, in particular a distributor in continuous steel casting for arrangement between a metallurgical vessel, such as a steel ladle or an electric arc furnace and a continuous casting mold with an inlet region and at least one outlet region, wherein in the inlet region liquid metal can be fed in in particular via at least one inlet and in the outlet region the liquid metal is discharged from the distributor in particular by means of at least one closure plug and at least one outlet correspondingly interacting therewith, wherein one, several or all of the following measures on the distributor for forming a singular, screw-like roller flow of liquid metal from an inlet to an outlet during continuous casting in the distributor are: a.the at least one inlet is arranged offset from a side wall, so that a metal flow at least partially hits an inner surface of the side wall and is deflected by this; b. a flow modifier is arranged below the inlet, which either has at least one impact surface arranged obliquely with respect to the vertical axis and / or the central axis or is designed as a deflection box with an opening in the direction of a side wall, wherein the impact surface or the deflection box is aligned such that metal flowing out of the inlet during continuous casting is deflected by the impact surface or the opening of the deflection box in the direction of an opposite side wall and a flow forms on this side wall up to a bath level; c.in the area of ​​a side wall, a gas purging element is arranged at the bottom and / or a gas purging element is arranged in the area of ​​the side wall in such a way that, during continuous casting, gas guided through the gas purging elements rises to the bath surface and forms a flow by entraining liquid metal; d. the outlet opening of the inlet is directed only in the direction of one of the side walls.

[0070] A further development provides for the impact surface of the flow modifier to be flat, convexly curved, or concavely curved and / or designed with a contour or recesses. Advantageously, the resulting flow can be implemented simply, efficiently, and robustly, both through the curvature on the one hand and the contour or recess as a second measure.

[0071] A further development provides that the gas purging elements are designed as gas purging stones, gas purging bars or the like in the floor and / or the side wall or on the floor or a side wall.

[0072] A further development provides that the gas purging elements are designed to form a flow from the distributor base to the bath surface, which overlays the existing flow from the inlet to the outlet and is 5 to 15 times the speed of the flow from the inlet to the outlet.

[0073] A further development provides for the distributor to be a longitudinal or transverse distributor. A further development provides for the distributor to have one or more inlets.

[0074] A further development provides that the distributor has one or more outlets.

[0075] A further development provides that the distributor has several distributor fingers, each with at least one outlet.

[0076] A further development provides that the outlet(s) are arranged 200 mm each and preferably less than 100 mm from the adjacent end wall.

[0077] A further development provides for the distributor base to be barrel-shaped and concave in order to support the flow formation.

[0078] A further development provides that the edges between the floor and the side walls are rounded or bridged with wedge-shaped elements.

[0079] A further development provides that the side wall, to which the shadow tube is arranged offset, is formed with a reinforced refractory support or a refractory plate in the area of ​​the inlet.

[0080] A further development provides that the outlet is arranged offset to a side wall with respect to the central axis of the distributor.

[0081] A further development provides that the outlet is offset in the same direction to the same side as the shroud. Another aspect of the invention relates to a method for continuously casting metals, wherein liquid metal is allowed to flow from a metallurgical vessel into a tundish via a shroud and the liquid metal is transferred into a mold via an outlet. The metal is guided in the tundish such that it exhibits a singular, helical roll flow from the inlet to the outlet.

[0082] A further development provides that the metallurgical vessel is arranged above the distributor in such a way that the shadow tube is located in the area of ​​a side wall of the distributor, so that liquid metal is guided along a side wall in the direction of a distributor base and is guided from the distributor base along an opposite wall to a bath level.

[0083] A further development provides that in the area of ​​a side wall in which an upward flow of the metal is generated, gas is blown in through gas purging stones, gas purging bars or other gas purging devices in order to intensify the flow.

[0084] A further development provides that the gas inlet devices form a flow from the distributor base to the bath surface, which overlays the existing flow from the inlet to the outlet and is 5 to 15 times the speed of the flow from the inlet to the outlet.

[0085] A further development provides that the liquid metal is guided from the metallurgical vessel via the shadow tube onto an inclined surface in order to deflect it towards a side wall.

[0086] A further development provides for the bottom of the distributor to be curved and concave, barrel-shaped, to promote flow formation. Another development provides for the edges between the distributor bottom and the distributor side walls to be designed as concave ramps.

[0087] A further development provides that the gas inlet devices create a flow of

[0088] A flow of metal from the distributor base to the bath surface is formed, which overlies the existing flow from the inlet to the outlet and is 5 to 15 times the flow velocity from the inlet to the outlet, with the gas being injected at a corresponding rate and speed. The gas flow is preferably more than 50 to 100 operating liters per minute.

[0089] A further development provides that at least 80%, preferably 90%, of the distributor cross-section is covered by the singular flow roller. This can preferably achieve increased yield and reduced inclusion frequency.

[0090] The invention is explained by way of example with reference to a drawing. It shows:

[0091] Figure 1: the state of the art with two counter-rotating vortex formations; Figure 2: a highly schematic view of a continuous casting plant;

[0092] Figure 3: a cross-section through a distributor with a flow modifier;

[0093] Figure 4: a longitudinal section through the distributor according to Figure 3; Figure 5: another embodiment of a distributor with a flow modifier and an inserted flushing bar remote from the flow modifier;

[0094] Figure 6: the distributor according to Figure 5 in a longitudinal section; Figure 7: another embodiment of a distributor with a flow modifier and two outlets adjacent to both end walls;

[0095] Figure 8: the distributor according to Figure 7 in a longitudinal section;

[0096] Figure 9: another embodiment of a distributor with a V-shaped flow modifier, a so-called V-distributor; Figure 10: a cross-section through a distributor with an inflow via a curved shadow tube;

[0097] Figure 11: a cross-section through a distributor with an inflow by means of a shadow pipe opened over the wall alignment;

[0098] Figure 12: a cross-section through a distributor with an inlet with a flow modifier designed as a deflection box;

[0099] Figure 13: isometric view of a deflection box;

[0100] Figure 14: Top view of a distributor with an obliquely arranged flow modifier; Figure 15: Top view of a distributor with a curved shadow tube directed obliquely toward a side wall, for example, according to Figure 10;

[0101] Figure 16: a representation of the residual time distribution behavior with and without inventive measure (flow modifier);

[0102] Figure 17: the inclusion concentration without and with inventive measure on the cast product, depending on the loading of the distributor, measured by the distributor weight;

[0103] Figure 18: the inclusion frequency per unit area, depending on the distributor weight and thus on the operating condition of the distributor over time.

[0104] A continuous casting plant 1 has a first metallurgical vessel 2, for example, a ladle 2 containing liquid metal. Arranged below this is a distributor 3, which is loaded with liquid metal via a shroud 4 arranged on the ladle 2. The shroud 4 can have one or more outlet openings 32. The distributor 3 is an elongated, preferably trough-like container with two opposing end walls 5, 6 and two side walls 7, 8 connecting the end walls.

[0105] In addition, the distributor 1 has a base 9, with an inlet area 11 and an outlet area 12 provided along a central axis 10 of the distributor 1. The inlet area 11 is arranged adjacent to an inlet-side end wall 5, while the outlet area 12 is formed adjacent to an outlet-side end wall 6, so that incoming steel generally flows through the vessel following the longitudinal extension of the distributor 3. However, the distributor can also be shaped differently, for example, V-shaped or with multiple fingers or multiple outlets.

[0106] The bottom 9 of the distributor 1 can deepen diagonally from an inlet area 7 to an outlet area 8, whereby diagonally means that the depth becomes deeper compared to a bath level 13.

[0107] In the outlet area 12, an outlet 14 with a pouring tube 15 is arranged in the bottom. The pouring tube 15 opens into a mold 16 in which the metal is cooled until solidification occurs. The strand 17 emerges from the bottom of the mold 16 and is deflected by refractory rollers 18, entering a straightening zone 19. After the straightening zone 19, the strand 17 is cut into slabs 21 by flame cutters 20.

[0108] Figure 3 shows a first measure for generating a helical roller flow 22. In this case, the shadow tube 4 is arranged in the inlet area 11 and extends through the bath level 13, which is covered on top by a layer of slag, into the distributor 3. From the shadow tube 4, the liquid metal from the metallurgical vessel 2 located above it enters the distributor 3 along a vertical axis 23. A flow modifier 24 is arranged in the region of the vertical axis 23 below the shadow tube 4. The flow modifier 24 is a triangular, ramp-like block which has an impact surface 25 which runs obliquely to the vertical axis 23 and is directed towards a side wall 7. This has an angle α of approximately 45° in this case.

[0109] The incoming metal strikes the impact plate 25, from where it is directed toward the wall 7 in the direction of the arrow 22. To avoid a dead space between the base 9 and the wall 7 and, in particular, to achieve a good deflection of the material from the impact plate 25 along the wall 7, either a ramp-like element 26 or a slope 26 formed through the wall 7 can be provided.

[0110] The flow modifier 24 is designed in a block-like manner and extends only over a part of the longitudinal extent 10 of the distributor, in particular only in the area below the shadow tube 4. Due to this deflection on the one hand and a flow in the direction of the pouring tube 15 on the other hand, a screw-like flow 22 (Figure 4) develops along the arrows 27 shown.

[0111] The pouring tube 15 is or can be closed as usual with a pouring plug 29 which is aligned and runs along a longitudinal axis 28 and extends into the melt.

[0112] In a further advantageous embodiment (Figure 5, Figure 6), in addition to the flow modifier 24, a flushing device 30 is arranged on or in the bottom 9 of the distributor.

[0113] The flushing device can be a gas purging plug or a gas purging bar which extends over a partial length of the longitudinal extension 10 of the distributor.

[0114] In addition, such a gas purging device can also be arranged as a gas purging device 31 on a wall 7 of the distributor, wherein these purging devices 30, 31 are arranged in particular in the region in which the metal flow runs in the direction of the bath level 13 in order to support the upward movement.

[0115] From Figures 3-6 it is also clear that the shadow tube 4 can also open into the distributor 3 eccentrically, ie offset relative to one of the walls 7, 8. In this case, it may be sufficient for the shadow tube 4 to be offset eccentrically relative to the wall 8, thus allowing the metal jet to flow along the inside of the wall 8, thus forming a desired helical flow pattern.

[0116] Accordingly, in this case, the distributor 3 must be arranged offset from the metallurgical vessel 2 located above it, in particular a casting ladle. Even with such a configuration, a flow modifier can be arranged in the region of the base 9 and the wall 8, connecting the two to each other, to support the formation of the helical, cylindrical flow.

[0117] In addition, the outlet 15 can also be arranged in the same direction as the shroud 4, offset from the transverse center of the distributor plate 9. This makes it possible to better maintain the helical roller flow up to the outlet 15. It then does not constrict as much as in the prior art (Figure 1).

[0118] In a further advantageous embodiment (Figures 7, 8), a distributor 1, which is also elongated and trough-shaped, has a central inlet 11 and an outlet 12 adjacent to each end wall; otherwise, the distributor is constructed identically. Thus, two helical roller flows 22 are formed.

[0119] Figure 9 shows an angled distributor 1, a so-called V-distributor, which also has a central inlet 11. Two distributor fingers 31 branch off from a central inlet area 30. The above statements also apply to this embodiment. Accordingly, two helical roller flows are formed, running at an angle to each other. 22.

[0120] In a further embodiment (Fig. 10 and Figure 11), the helical roller flow 22 is induced by the shape of the shadow tubes 4, whereby other measures such as flow modifiers or gas purging elements are not excluded.

[0121] Here, the shadow tube 4 is provided in the lower area with a curved outlet opening 32, which points toward a side wall 7, 8 of the distributor 1. The outlet opening of the inlet 4 can be open or directed toward an outlet 15 at an angle ß of, in this case, approximately 30° relative to the y-axis; this is shown in the plan view in Figure 15. The angle ß can, of course, also be varied and can take a value from -45° to 45°.

[0122] In a further embodiment (Figure 11), the shadow tube is closed at the bottom but is formed with a lateral outlet opening 32. This also deflects the liquid metal laterally, thereby generating the roller flow 22.

[0123] Figure 14 shows a further embodiment in which the flow modifier is aligned at an angle ß of, for example, 30° relative to the y-axis in the direction of an outlet 15.

[0124] Figure 12 shows an inflow of the metal stream, the flow modifier in this case being designed as a deflection box 34 with an opening 35 to a side wall 7. The melt is introduced via the shadow tube 4 and deflected by the opening 35 of the deflection box 34, so that the liquid metal is deflected laterally and the roller flow 22 is thereby generated. Figure 13 shows an exemplary deflection box 34 according to the invention, which has an opening 35. This deflection box 34 can also have a plurality of openings 35, which, however, according to the invention may only be directed towards one side wall 7. The base of the deflection box can be flat or curved or can also have grooves or other indentations.Furthermore, a nozzle-like impulse of the melt can also be provided within the deflection box, but in any case the steel melt should be deflected in the direction of a side wall so that the liquid metal is deflected laterally and the roller flow 22 is thereby generated.

[0125] Figure 16 shows the flow behavior of a liquid metal in the distributor 3. The curve, with the flow-influencing measures according to the invention, clearly also demonstrates good flow efficiency because the metal stream has a comparatively long residence time, which accordingly maximizes the deposition of unwanted particles. This results in a lower inclusion concentration in the metal stream at the outlet.

[0126] Figure 17 shows the distributor weight versus the casting capacity and the inclusion concentration in the cast product. This clearly shows that without the measures according to the invention, especially when the distributor is refilled (after a ladle change), the inclusion concentration increases significantly. With the formation of the helical roller flow according to the invention, the inclusion concentration in the cast product is significantly lower even when the distributor is refilled. This can also be seen in Figure 18, which shows the inclusion frequency per unit area.

[0127] In general, it should be noted with regard to the figures that the term "flow modifier" refers to the measures according to the invention and does not necessarily require the installation of a flow modifier.

[0128] In all figures, a deflection to the left side wall 7 is shown as an example. Of course, a mirror-inverted deflection to the right side wall 8 is also possible and would result in the same helical roller flow according to the invention. The invention therefore has the advantage that both the filling and emptying of the distributor can take place without an accumulation of inclusions, and the filling efficiency of the distributor is also improved.

Claims

Patent claims 1. Continuous casting plant for continuous metal casting, comprising at least a first metallurgical vessel (2) and a distributor (3) arranged underneath, wherein an inlet (4) with an outlet opening (32) for liquid metal is arranged from the first metallurgical vessel (2) into the distributor (3) and the distributor has at least one outlet (15) which opens into a casting mold (16), wherein the distributor (3) has at least two end walls (5, 6), at least two side walls (7, 8) and a bottom (9), characterized in that in order to form a singular, helical roller flow (22) of liquid metal from an inlet (4) to an outlet (15) during continuous casting in the distributor, one, several or all of the following measures are provided: a.the inlet (4) from the metallurgical vessel (2) into the distributor (3) is offset from the central axis (10) to a side wall (7, 8), so that during continuous casting a flow of the incoming liquid metal is formed along a first side wall (8), then along the bottom (9) and on the opposite side wall (7) again in the direction of a bath level (13); b.a flow modifier (24) is arranged below the inlet (4), which either has at least one impact surface (25) arranged obliquely with respect to the vertical axis (23) and / or the central axis (10) or is designed as a deflection box (34) with an opening (35) in the direction of a side wall (7, 8), wherein the impact surface (25) or the deflection box (34) is aligned such that, during continuous casting, metal flowing from the inlet (4) is directed by the impact surface (25) or the opening (35) of the deflection box (34) in the direction of an opposite side wall (7, 8) and a flow is formed thereon upwards to a bath level (13); c.in the region of a side wall (7, 8) a gas purging element (30) is arranged on the bottom (9) and / or a gas purging element (31) is arranged in the region of the side wall (7, 8) in such a way that during continuous casting gas guided through the gas purging elements (30, 31) rises to the bath level (13) and forms a flow by entraining liquid metal;. d. the outlet opening (32) of the inlet (4) is directed only toward one of the side walls (7, 8). Continuous casting plant according to claim 1, characterized in that the impact surface (25) of the flow modifier (24) is flat, convexly curved, or concavely curved and / or is formed with a contour or with depressions. Continuous casting plant according to claim 1 or 2, characterized in that the distributor is a longitudinal or transverse distributor or V-distributor.Continuous casting plant according to one of the preceding claims, characterized in that the outlet opening of the inlet (4) is open or shaped so as to be directed at an angle ß of -45° to 45°, preferably 0° to 45°, in particular 0° to 20°, preferably 0° to 10°, particularly preferably 1° to 5°, relative to the y-axis in the direction of an outlet (15), wherein the spatial orientation is such that the Z-coordinate axis denotes a normal direction which runs perpendicular to the surface of the distributor, the X-coordinate axis points in the metal flow direction from the inlet (4) in the direction of an outlet (15) in the distributor, and the Y-coordinate axis points in the transverse direction of the metal flow in the distributor in the direction of the outlet (15). Continuous casting plant according to one of the preceding claims, characterized in that the distributor has one or more inlets (4).Continuous casting plant according to one of the preceding claims, characterized in that the distributor has one or more outlets (15). Continuous casting plant according to one of the preceding claims, characterized in that the at least one inlet (4) from the metallurgical vessel (2) is arranged adjacent to an end wall (5), and the at least one outlet (15) is arranged adjacent to the opposite end wall (6). Continuous casting plant according to one of the preceding claims, characterized in that the distributor has a plurality of distributor fingers, each with at least one outlet. Continuous casting plant according to one of the preceding claims, characterized in that the outlet(s) are each arranged at a distance of less than 200 mm and preferably less than 100 mm from the adjacent end wall. Continuous casting plant according to one of the preceding claims, characterized in that the gas purging elements (30, 31) are designed as gas purging bricks, gas purging beams, or the like in the base (9) and / or the side wall (7, 8) or on the base (9) or a side wall (7, 8).Continuous casting plant according to one of the preceding claims, characterized in that the gas purging elements are designed to form a flow from the distributor base to the bath level, which flow is superimposed on the existing flow from the inlet to the outlet and is 5 to 15 times the velocity of the flow from the inlet to the outlet. Continuous casting plant according to one of the preceding claims, characterized in that the distributor base (9) is designed with a barrel-shaped, concave arch to support the flow formation. Continuous casting plant according to one of the preceding claims, characterized in that the edges between the distributor base (9) and the side walls (7, 8) are rounded or bridged with wedge-shaped elements (26).Continuous casting plant according to one of the preceding claims, characterized in that the side wall (8), to which the inlet (4) is arranged offset, is formed with a reinforced refractory support or a refractory plate in the region of the inlet (4).

15. Continuous casting plant according to one of the preceding claims, characterized in that the outlet (15) is arranged offset relative to a side wall (7, 8) with respect to the central axis (10) of the distributor (9).

16. Continuous casting plant according to one of the preceding claims, characterized in that the outlet is offset in the same direction to the same side as the inlet (4).

17. Distributor, in particular distributor in continuous steel casting for arrangement between a metallurgical vessel (2), such as a steel ladle or an electric arc furnace, and a continuous casting mold (1) with an inlet region (11) and at least one outlet region (12), wherein in the inlet region liquid metal can be fed in particular via at least one inlet (4) and in the outlet region (12) the liquid metal is discharged from the distributor (3) in particular by means of at least one closure plug (29) and at least one outlet (15) correspondingly cooperating therewith, characterized in that one, several or all of the following measures are provided on the distributor (3) for forming a singular, screw-like roller flow (22) of liquid metal from an inlet (4) to an outlet (15) during continuous casting in the distributor: a.the at least one inlet (4) is arranged offset from a side wall (7, 8) so that a metal stream impinges at least partially on an inner surface of the side wall (7, 8) and is deflected by it; b. a flow modifier (24) is arranged below the inlet (4), which either has at least one impact surface (25) arranged obliquely with respect to the vertical axis (23) and / or the central axis (10) or is designed as a deflection box (34) with an opening (35) in the direction of a side wall (7, 8), wherein the impact surface (25) or the deflection box (34) is aligned such that, during continuous casting, metal flowing from the inlet (4) is deflected by the impact surface (25) or the opening (35) of the deflection box (34) in the direction of an opposite side wall (7, 8) and a flow is formed thereon upwards to a bath level (13);. c. in the region of a side wall (7, 8), a gas purging element (30) is arranged on the bottom (9) and / or a gas purging element (31) is arranged in the region of the side wall (7, 8) in such a way that, during continuous casting, gas guided by the gas purging elements (30, 31) rises to the bath level (13) and forms a flow by entraining liquid metal; d. the outlet opening (32) of the inlet (4) is directed only in the direction of one of the side walls (7, 8).

18. Distributor according to claim 17, characterized in that the impact surface (25) of the flow modifier (24) is flat or convexly curved or concavely curved and / or formed with a contour or with depressions.

19. Distributor according to claim 17 or 18, characterized in that the gas purging elements (30, 31) are designed as gas purging stones, gas purging bars or the like in the base (9) and / or the side wall (7, 8) or on the base (9) or a side wall (7, 8).

20. Distributor according to one of claims 17 to 19, characterized in that the gas purging elements (30, 31) are designed to form a flow from the distributor base to the bath level, which flow is superimposed on the existing flow from the inlet to the outlet and is 5 to 15 times the speed of the flow from the inlet to the outlet.

21. Distributor according to one of claims 17 to 20, characterized in that the distributor base (9) is barrel-shaped and concavely curved to support the flow formation.

22. Distributor according to one of claims 17 to 21, characterized in that the edges existing between the base (9) and the side walls (7, 8) are rounded or bridged by wedge-shaped elements (26).

23. Distributor according to one of claims 17 to 22, characterized in that the side wall (8), to which the inlet (4) is arranged offset, is formed with a reinforced refractory support or a refractory plate in the region of the inlet (4).

24. Distributor according to one of claims 17 to 23, characterized in that the outlet (15) is arranged offset relative to a side wall (7, 8) with respect to the central axis (10) of the distributor (9).

25. Distributor according to one of claims 17 to 24, characterized in that the outlet is offset in the same direction to the same side as the inlet (4).

26. A method for continuously casting metals, wherein liquid metal is allowed to flow from a metallurgical vessel (2) via at least one inlet (4) into a distributor (3) and the liquid metal is transferred via at least one outlet (15) into a mold (16), characterized in that in the distributor the metal is guided in such a way that it executes a singular, screw-like roller flow from an inlet (4) to an outlet (15).

27. The method according to claim 26, characterized in that the metallurgical vessel (2) is arranged above the distributor (3) such that the inlet (4) is located in the region of a side wall (7, 8) of the distributor (3), so that liquid metal is guided along a side wall (7, 8) in the direction of a distributor base and is guided from the distributor base (9) along an opposite wall (7, 8) to a bath level (13).

28. Method according to claim 26 or 27, characterized in that in the region of a side wall (7, 8) in which an upward flow of the metal is generated, gas is blown in through gas purging bricks, gas purging bars or other gas purging devices in order to intensify the flow.

29. Method according to one of claims 26 to 28, characterized in that the liquid metal is guided from the metallurgical vessel via the inlet (4) onto an impact surface (25) or via a deflection box (34) in order to deflect it in the direction of a side wall (7, 8).

30. Method according to one of claims 26 to 29, characterized in that the bottom (9) of the distributor is curved in a barrel-like concave shape in order to support the flow formation.

31. Method according to one of claims 26 to 30, characterized in that the edges between the distributor base (9) and the distributor side walls (7, 8) are designed as concave ramps.

32. A method according to any one of claims 28 to 31, characterized in that the gas inlet devices form a flow of the metal from the distributor base to the bath level, which flow is superimposed on the existing flow from the inlet to the outlet and is 5 to 15 times the velocity of the flow from the inlet to the outlet, the gas being injected at a corresponding quantity and velocity.

33. Method according to one of claims 26 to 32, characterized in that at least 80%, preferably 90%, of the distributor cross-section is covered by the singular flow roller.

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