DE1917367A1 - Process for the continuous casting of steel and continuous casting plant for carrying out the process - Google Patents

Description

Addition to patent application P 15 03 959.5

As is well known, the manufacture of continuous steel castings is proportionate cheap, partly because, on the one hand, the classic chill casting by trimming each rod at the bottom and especially at the upper end occurring steel losses can be avoided, and because on the other hand the casting with small Cross-section takes place, which reduces the processing costs compared to the permanent mold casting with a large * rod cross-section will. In addition, the quality of the steel is improved, on the one hand because of the better cross-sectional properties, which require less machining to equalize the final cross-section, and on the other hand vreil the rapid solidification that is continuously in parallel stripes takes place, preventing any increase or segregation, so that the properties of the steel from the beginning are uniform up to the end of the cast bar and the chemical composition is uniform from the edge to the core of the cast rod. This homogeneity is desirable for many reasons, for example because of the larger

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Constancy of the deformations that result from hardening the machined. Parts occur.

In general, it is necessary for the cast rod, the cast rings of which are solidified by cooling, to be applied from above to slide down through the tubular mold, to lubricate between the cast rings and the copper wall of the mold. In addition mineral oil is usually allowed to run onto the surface of the steel bath and onto the mold walls. In this way will sticking or hanging of the continuous casting rod on the inner wall of the mold avoided. *

On the other hand, it is known to manufacture steels whose machinability with cutting tools can be facilitated by suitable additives. As additives sulfur and dlei and other things come into consideration, but the addition of tellurium gives much more interesting properties than the aforementioned two elements in that the performance properties are hardly changed, while the machinability with cutting tools improves to a much greater extent than with the addition from sulfur and lead. Steels with a tellurium content between 0.02 and 0.10% are also very popular. These steels are produced by the usual chill casting process, the tellurium being added in most cases in the form of small grains during casting, from the point in time when a quarter of the steel has been poured into the chill and until the chill is completely with it Steel is filled. Whichever technique is used, there is a certain unevenness in the distribution of the tellurium, which results either from the time the tellurium is added, from losses through evaporation or combustion in the air, or from the formation of cavities during solidification. Therefore, the tellurium content in the outer layers of the rod is insufficient and becomes excessively high in the core area of the rod and especially in the upper part. The performance properties and the machinability are therefore not favorable.

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Attempts have also been made to cast tellurium steel manufacture to overcome these drawbacks; however, all attempts so far have failed, and a tellurium steel strand could not be produced. The reason for these failures is to be seen in the fact that when trying to produce a tellurium steel casting, experienced a series of very violent explosions in the mold, which would cause severe damage if the attempt was not made broke off immediately »The cause of these explosions could not be determined. In addition to this recoverable grievance If the steel casting jet between the tundish and the mold leads to tellurium losses as a result of evaporation and oxidation, and the vapors which are formed are very harmful to the hessian workers.

The main patent relates to continuous casting, which is carried out in a plant that has at least one tubular copper mold, which is charged with liquid steel via an intermediate vessel, which in turn is charged from a steel casting ladle and which has an interior space in whose bottom i..Iruiestens a closable outlet for charging the mold is provided; the steel is sealed off from the atmosphere by a dip tube made of porous sintered glassy silicon dioxide, while it flows from the tundish into the mold, the lubrication between the copper surface of the mold and the solidifying steel in the mold by a synthetic slag, but not with organic 'oil, can be done. The slag that covers the steel in the mold is chosen so that the viscosity and the wetting capacity of the material in relation to the copper as well as the steel allows it to penetrate by capillary action between the copper of the mold and the solidifying steel and between copper and Steel to produce an extremely thin separating layer.

The creation of a reducing atmosphere in

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the intermediate vessel, the protection of the metal surfaces in the Plant with a thin layer of synthetic slag and covering the slag welding by a powder refractory substance piIt thermal insulation properties, such as graphite, advantageously lead to very favorable results.

The ladle can be inserted into the intermediate vessel straight pipe running essentially perpendicularly from porous sintered vitreous filicium dioxide ent leren-; this tube serves as an extension of one in the bottom of the ladle provided fireproof outlet and a moving shutter like a plug can be placed on the opening of the spout. The pipe that can come out of the ladle can also curved, executed, and the outflow · ", control points to a drive device, which is operated in such a way, that the ladle around. a horizontal axis is tiltable, which runs through the outlet opening of the pipe whose The inlet opening is close to the testicle of the pouring ladle and as close as possible to this axis.

The tubes made of porous sintered glassy silicon dioxide are manufactured according to the usual methods. "For this purpose, glassy silicon dioxide can be ground in powder form and floated in pure water, to which a preferably organic emulsifier has been added, in order to produce a paste which is then converted into a porous plaster of paris mold is poured, in which the powder settles uniformly as a consistent crust on the bands; then the excess pulp is poured out and is removed from the mold by opening the plaster mold, dried and sintered, as is known from Xerano technology, including the: 'asse is pressed under high pressure at a temperature between 1100 and 1200 ⁰ C, that is below the melting or devitrification temperature.

The above process steps, which form the subject of the main patent, enable the solution of the "next

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task given above, namely in the continuous casting process to manufacture all types of steel with additives, "those made of tellurium, selenium, a mixture of both or chemical compounds with one of these elements.

The invention now relates to a method of application the arrangement described in the main patent; the method is characterized in that under the specified production conditions Tellurium or selenium is added to the ladle that is used to make the To direct steel from the steel furnace into the continuous casting plant, or that these additives in the tundish Mschen ladle and mold are introduced, in the latter case in the form of fine grains progressively throughout Casting process »

It is noteworthy that under these circumstances the continuous casting proceeds perfectly without any tellurium or selenium losses, without the occurrence of toxic fumes and without the slightest explosion phenomena. You can get out of it conclude that the explosions by reaction between the tellurium or the selenium and the organic oil or its Degradation products were caused, because if you make the casting in conventional molds, but after you have the walls has coated the mold with mineral oil, violent explosions occur that do not even allow the mold to be filled, While the same process goes on without incident, if the steel is free of tellurium or selenium.

According to the invention, steels with a tellurium content of 0.02 to 0.10% can thus be processed in the continuous casting process.

It ve ^{1 found} that the tellurium-containing steel rods, which were manufactured according to the invention by the continuous casting process and then rolled, have very vid better properties than rods of the same cross-section, which were cast in conventional molds and then rolled. The processing

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The availability was much better, as were the mechanical properties. That stems from a very much joyful "- · massive distribution of tellurium and of courtesy made to adjust the tellurium concentration much more precisely to a certain! 'Jert. The homogeneity in question extends both on the distribution in a cross-sectional area between the core and the edge zone than on the distribution along the rods from the beginning to the end of a uniform Cast strand.

The above applies to all types of steel: to very low carbon Steels (less than 0.15 percent by weight), for steels with any carbon content up to very high carbon (maximum 0.80 percent by weight), for all types of alloyed structural steel with additions of nickel, chromium, Molybdenum etc. usual content. The process can also be used with steels that contain sulfur in addition to tellurium, or lead in addition to tellurium, or contain sulfur, lead and tellurium at the same time, - these additives being used to improve the energy efficiency can be applied by cutting tools.

The invention also relates to a design of the intermediate vessel, after which it is possible in a particularly advantageous manner in the metal tellurium, selenium, a mixture of both or introduce a chemical compound of one of the two elements.

The arrangement thus relates to an object of the Main patent forming devices, in particular on an intermediate vessel which has a vault, which the ambient air from the steel in the tundish, which the latter is to be provided with a pipeline which is a Inert, neutral or reducing gas allows the introduction, which then the atmosphere in the interior of the vessel forms. The arrangement is characterized in that the intermediate vessel has at least one opening for feeding of additives that are in the intermediate vessel near the point

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opens at which the pouring stream coming from the pouring ladle penetrates into the liquid steel located in the intermediate container.

Γ-in v; the above-mentioned constructed intermediate vessel allowed advantageously also not only in the bathroom the mentioned To introduce additives, but also to use aluminum as a sedative or in a very similar way '' Add very dense additives, such as lead, galena or iron sulphide, etc., to the liquid metal.

The invention therefore also relates to production of a new type of lead-containing steel.

"oh the. üau" tpatent enabled the disoxidation or facilities serving to calm down the steel to improve the final Γ-calming of the steel when it is in the furnace or in the ladle through the classic elements (manganese, silicon, calcium silicon, etc.), but not with Aluminum, was pacified by that. the experts agree assumed that it was not suitable for continuous steel casting.

scrcrw ^ can now complete the calming and also the regulation of the grain of the steel Addition of aluminum or an alloy of aluminum nit 0.5 to 1? &! Magnesium can only be used. Through the '.'snd of the intermediate vessel or through the vault becomes a Immersion tube made of porous sintered glassy silicon dioxide led that is below the intended level of the liquid Steel opens near the point at which the pouring stream enters the intermediate vessel. There is also a transport device provided with which a tape or a wire made of light metal is pushed into the tube at one speed which is not so large that the Γ metal band still in the solid state in the liquid steel in the vessel

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The steel in the tundish is covered by a layer of slag of suitable composition; the slag can be made from a eutectic based on SiO ₂ , CaO, Al ₃ O ₃ with flux or reducing additives. The vault on the. The intermediate vessel protects the slag from cooling down.

The attachment of the vault and the introduction of a gas ensure good thermal and chemical protection of the Steel. In this case one can use a reducing (read, say Propane, but the steel cannot absorb any hydrogen because of the layer of slag that covers it.

In order to achieve a better distribution of the aluminum in the steel, and before the steel reaches one of the outlets opening into the mold, a lateral approach is expediently provided on the intermediate vessel, which has an inlet opening on its upper side for the pouring stream emerging from the pouring ladle owns; the entry opening for the steel additives is also provided in the attachment, and said opening is connected to the lower part of the interior space by a channel located under the metal surface.

Since the channel remains submerged, there is also the cavity between the vault and the free steel surface sealed in the intermediate structure which contains the gas atmosphere; the slag is also held back and cannot move into the approach. In this way, slags and reaction inclusions can rise and are removed from the The layer of slag that covers the steel bath in the tundish is collected.

So that a good (uniformity of the composition of the liquid steel is guaranteed before it passes through an outlet gets into the IC mold, at least one low intermediate wall made of refractory material can be in the intermediate vessel

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be provided on the bottom of the intermediate vessel in the direction of flow above the outlet transversely to the flow path of steel is built; the upper edge of the low wall is below the intended minimum level of the liquid steel,

The low wall forces the steel coming from the approach to ascend when he continues to run into the intermediate vessel.

So far, the addition of substances of high density to the steel resulted in substances such as lead, ullage, sulfur iron, Selenium, tellurium and their chemical compounds, great difficulties in the continuous casting process or the addition was impossible.

It is known, for example, that under normal conditions continuous casting is not possible to produce lead-containing free-cutting steels. In these steels lies the Lead content generally between 0.10 and 0201. The lead is usually placed in the casting mold in the pouring stream, and it is known that lead, which is denser than steel, immediately collects in the axis of the mold in which Tip of the inverted cone that forms the interface between the already solidified and the non-liquid steel. This distribution makes the steel for its intended use not suitable.

What has been said here for lead applies equally to them other heavy additives mentioned above,

It has now been shown that systems according to the invention with immersion pipes between the intermediate vessel and the molds, with intermediate vessels that have a lateral attachment, and are equipped with a low wall, do not have these disadvantages.

You can © in an immersion tube made of slightly sintered glassy silicon dioxide add the steel ladle and the approach of the

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Use intermediate vessel, which is particularly useful: because this avoids the oxidation of the steel in the pouring stream and thus does not rule out the possibility is to introduce lead granules into the area around the pipe reaching into the lateral approach. In this case make up the device for introducing additives and the opening a uniform component for receiving the steel pouring stream from the pouring ladle.

Remarkably, the one in one, according to the invention Plant produced lead-containing steel a uniformity in the distribution of the lead, which is the case with classic permanent mold casting cannot be reached. This results in a uniformity which is very favorable for the machinability of the steel and you can be sure of a very high cutting speed and very little wear and tear on the cutting tools to adjust; that makes this steel very valuable. These steels must therefore be considered completely new products and the invention includes these products as well.

Various embodiments of the invention are shown below and their special features are explained on the basis of drawings that show the execution / forms schematically represent.

Fig. 1 is a schematic diagram of an arrangement for introducing aluminum into the steel bath in the zirconia vessel;

FIG. 2 shows another form of filling of the one shown in FIG Construction; the intermediate vessel is then equipped with a lateral attachment;

Fig. 3 shows an arrangement in which substances of very high density are to be introduced and the in A low wall is provided between the vessel;

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Fig. 4 shows a modification of the intermediate vessel Approach and low wall; the arrangement is so found slag easy to peel off;

FIGS. 5 to 7 give sectional images of an arrangement Four molds-again, whereby the intermediate vessel is provided with two low walls *

All brackets, locking devices, overhead surveillance devices, Executions. For serving, for! Tempering, for cooling and for heating, etc., which are known per se in continuous casting plants, have not been shown here.

Genä ^p v FIG. 1 is a nit a vault 3 Covered Zwischengefäi 2 is beschielet from a ladle 1. After emerging from the outlet 4 of the pouring ladle 1, the jet 5 of liquid steel flows through an opening 6 in the vault

Between the vault and the mirror of the liquid metal becomes an atmosphere of a suitable, through which by the Gewiilbe 3 guided pipeline 8- maintained gas to be added.

A dip tube 9 made of porous sintered glassy silicon dioxide enters through the '' and of the intermediate vessel 2 and opens below the intended level of the liquid steel near the point where the jet 5 of liquid steel rat the steel bath 7 mixes. From a supply reel 10 An aluminum wire or band 11 can be unwound and middled a conveyor device, which can consist of two conveyor rollers 12 moving in opposite directions, is pushed into the tube 9 will.

The intermediate vessel 2 has as many outlets as there are molds

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are to be supplied from the vessel. In the embodiments shown in FIGS. 1 to 1, only one outlet 13 is provided on the intermediate vessel, which can also be closed with a closure piece (not shown), for example with a stopper and the associated from Hand, semi-automatic or fully automatic controlled stopper rods. The outlet 13 "continues into a refractory tube 14 made of porous sintered glassy silicon dioxide, the lower end of _{which protrudes a certain distance into a conventional, vertical tubular mold IS, for example a double-walled 9} water-cooled copper mold" The length of the tube 14 is so great selected that the pipe outlet dips into the liquid steel during the casting process, which is covered by a layer of slag 16; the level of the liquid steel is kept exactly constant because the rod 17 is drawn off under the action of gravity or driven by an arrangement of driver rollers, not shown.

The steel in the intermediate vessel 2 also has a layer of lacquer 13 covered.

The tubes 9 and 14 made of porous sintered glassy silicon dioxide are produced according to the usual processes. They can be manufactured by producing glassy silicon dioxide, ground powdery and absorbed in pure water mixed with an emulsifier; as emulsifiers are preferred organic substances are selected, and the resulting paste is placed in a mold made of porous plaster of paris in which the Powder settles uniformly as a consistent crust on the walls; the excess pulp is poured out of the mold, by opening the plaster mold, the tube is removed from the mold, then dried and sintered; this technique is for making ceramic parts well known.

The modified embodiment shown in FIG. 2 differs from the embodiment of FIG. 1 by one after

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Lateral approach 19 which is open at the top and which extends from one side of the intermediate vessel 20. The approach is separated from the interior 21 of the intermediate vessel by a partition made of refractory material, which in its lower ¹ Ml leaves free a channel 23 located entirely in the steel bath, via which the attachment 19 is in communication with the interior 21.

As with the arrangement described above, it also ends here an arrangement 9 to 12 for introducing additives at the point where the jet 5 of liquid steel in the metal bath penetrates, in this case into the steel bath located in attachment 19. ·

The intermediate vessel 24 of FIG _e 3 v / eist to even a low Hauer 25, which stands on the floor of the tundish immediately downstream relative to the baffle 22 and upstream relative to the outlet 13; the upper edge of the low wall 25 lies below the intended minimum level of the steel bath 7.

The stream of liquid steel moves on the path indicated by the arrows and the refractory partition 22 causes the airtight seal between the vault 3 and the surface of the steel bath 7 in the intermediate vessel and holds back the slag 18 in the vessel so that it can not pass into the approach 19, while excretions and Pvealctionsprodukte can rise and in the Slag 18 are collected, which covers the steel bath in the container 24.

Incidentally, the atmospheric oxidation of the steel on the way between the ladle 1 and the side Prevent approach 19 thereby that a dip tube 26 made of porous sintered glassy silicon dioxide under the ladle is attached and further the steel in the side approach with a cover 27 made of synthetic, sufficient

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refractory slag material is provided.

The insertion opening for the additives can as an immersion tube 9 (Fig. 5} be formed, or may nan for the upper opening 28 select through which the steel beam 5 enters 19 (Fig. 3) in the neck. _V

It can be seen from the drawings that when heavy substances, such as lead, are added, these substances lead to the outlet 13, which opens into the mold 15, cannot be reached directly by gravity. This heavy hike will prevented by the low! lauer 25. Therefore, with this arrangement, the lead can only move the low © wall 25 in one overcome movement leading from the bottom up; must it can either be dissolved in the steel or be very finely divided. The T.'irbelbew-egungen in the approach 19 and in the connecting channel 23 between the extension 19 and dee actual vessels facilitate both the dispersion and the dissolution of the heavy material.

The intermediate vessel 29 shown in FIG. 4 has on the one hand a low tusk 30, the upper edge of which is sharp Edge 31 is formed, which merges with an inclined plane 32 into the bottom 33 of the intermediate vessel and other » on the other hand an angled outlet 34, which is in the horizontal. Extension of the approach is and with its lower part connected is. This configuration makes it possible after Completion of the casting process, the synthetic slag 35 through simply tilting the vessel around the spout 34 or better around an axis 37 in the direction of arrow 38 completely into one Drain the slag pan 36.

If a malfunction occurs during the casting process that leads to Forcing interruption of the pouring, the can still be in that Tilting steel in a tundish to the. Place of the trough 36 normal® mold cast κ ° · the.

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From the Pig. 5 to 7 shows that the low Hauer can be divided into two parallel-mounted low walls 39 and 40 _t run through the intermediate vessel in its entire length and sindj arranged on either side of the vertical Schnittöbene FIG, S so that a syiainetrische off the off run achieved. The arrows mark the path of the molten metal «

With the addition of lead, this arrangement enables a great deal equal distribution of Schve metal in facilities for four-strand casting »in which the cast strands are symmetrical are arranged in the manner of a square (Fig. 6).

Claims;

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Claims (1)

Patent claims: Method for using a continuous casting plant with a tubular mold made of copper, which can be charged with liquid steel from a tundish, which in turn is filled from a ladle, after which - On the one hand, the steel when passing the intermediate vessel on the VJege to the mold against the atmosphere means a dip tube made of porous sintered glassy silicon dioxide is completed and - on the other hand, the lubrication between the copper wall the mold and the steel solidifying in the mold by means of a non-organic oil s> Tithetical slag takes place, which the steel in the mold covers and is chosen such that the viscosity and the wettability of the material against the copper such as the steel allows it to penetrate by capillary action between the copper of the mold and the solidifying steel and to create an extremely thin separating layer between the copper and the steel, characterized in that tellurium or selenium, a mixture of both or a chemical compound of one of these elements can be added as an additive, either into the ladle while it is being filled from a steel furnace and before the steel is discharged into the tundish, or into the tundish in a progressive manner uninterrupted during the entire casting process. 2. The method according to claim 1, characterized in that Tellurium in a Henge between 0.02 and 0.10 percent by weight, 009887/0707 _B AD ORIGINAL based on the total amount of metal to be cast, is added. Steel obtained by the specified process, thereby characterized in that the tellurium is distributed in the metal with a uniformity that soi / ohl the distribution of the tellurium in the cross section between the core and the edge as well the distribution over all poles from start to finish of a cast concerns. 4, plant for the continuous casting of steel and for practicing the method according to claim 1 with a pouring ladle, the pouring stream of which leads into an intermediate vessel which is covered with a vault and an interior space. on \\ travels, at the bottom of which at least one closable outlet is attached, which continues as an essentially vertical refractory tube made of porous sintered glassy silicon dioxide in order to charge at least one cooled tubular mold, the lower end of the tube during pouring into the The mold protrudes, while the air in the interior can be exchanged for another atmosphere by means of a gas supply line which opens into the intermediate container, according to the main patent, characterized in that the intermediate vessel ( ² J ²⁰ J ² ^; 29) has at least one has opening for the supply of additives, which opens into the intermediate vessel near the point at which the pouring stream (5) coming from the pouring ladle (2) penetrates into the liquid steel (7) located in the intermediate container. 5, continuous casting plant according to claim 4, characterized in that the container C20; 24; 29} with a horizontally in front 00988-770707 BATH ORIGINAL jumping lateral approach (19) is provided, at the top of which has an opening (28) for collecting the from the Pouring ladle (1) coming pouring stream is provided that also the introduction opening for additives also in the Approach is provided, and that finally the opening (28) through a submerged channel (23) with the the lower part of the interior (21) is connected * Continuous casting plant according to claims 4 and / or 5, characterized characterized in that the introduction opening for additives is designed as a dip tube (9) made of porous sintered glassy silicon dioxide, which the "and of the intermediate container (2i 2Oj 24) and below that for the liquid Steel (7) provided level opens near the point at which the pouring stream (5) into the in the intermediate container (2) located liquid steel penetrates, and that the additional substance introduced into the dip tube (9) in wire or tape form (11) by means of a conveyor device (12) and is pushed through the tube. 7 Continuous casting plant according to Claim 5, characterized in that that the introduction opening for additives with the opening (28) is connected to catch the pouring stream 8. Continuous casting plant according to one of claims 5, 6 or 7, characterized in that the intermediate container (24 j 29) at least one low one made of refractory material Wall (25; 30) which crosses the interior and on the container bottom downstream with respect to the channel (23) and upstream with respect to the outlet (13) is set, and that the upper edge of the low wall below the intended minimum level of the intermediate 009887/0707 ■■ ORIGINAL liquid steel located in the container. 9. Continuous casting plant according to claim 8, characterized in that the intermediate container (29) has only a low transverse wall (30), the upper edge of which is formed by an inclined edge G51) which is in a position opposite the bottom (33). inclined inclined surface (32) passes over that an outlet opening (34) is connected in the horizontal extension of the approach with its lower part, and that also the Intermediate container (29) around a horizontal, perpendicular to the vertical syrametric plane of the outlet opening, of the approach and the axis (37) extending inside the interior is tiltable. 10. Continuous casting plant according to claim 8, characterized in that that two low walls (39, 40) on both sides of the longitudinal vertical plane of symmetry that the approach and crosses the interior, are arranged. 11. Continuous casting plant according to one of claims 4 to 10, characterized characterized in that the pouring stream emerges from the pouring ladle through a closable outlet (4) which continues into a refractory tube (26) made of porous sintered glassy silicon dioxide, the end of which is below the for the steel in the intermediate container CW) Minimum level is. 12. A method for using the continuous casting plant according to the claims 4 to 11, characterized in that one of the following substances is selected as additives: aluminum, an aluminum-magnesium alloy, lead, lead sulfide, iron sulfide, tellurium, selenium and chemical compounds with 00 98 87/0707 BATH ORIGINAL Tellurium and selenium. 13. The method according to claim 12, characterized in that a slag (13) the liquid steel in the interior and / or the approach covered. 14, free-cutting steel with lead, manufactured in the strand casting plant according to one of claims 4 to 11. 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