The invention relates to a sealing system according to the preamble of Claim 1 , and to a refractory spout casing.

This type of arrangement is used, for example, for the casting of steel by the continuous casting method. The spout forms the outlet of a slide gate of a metallurgical vessel here. The casting tube connected to said spout in an air-tight manner conveys the molten steel into a die suitable for the purpose.

It is well known that the sealing system between the spout casing and the casting tube serves to prevent ambient air from being sucked into the molten steel through their connection seat when casting. For this purpose inert gas is supplied to the region of the connection seat, and the gas pressure of said inert gas counters the suction effect of the molten steel flowing through when casting. This type of sealing system is disclosed by DE 40 24 520 A1. A disadvantage of the latter is that the supply of the sealing system with inert gas is structurally complex and in addition is expensive, both due to the quantities of gas required and due to the gas pressure required. The object underlying the invention is to avoid these disadvantages and to provide a sealing system of the type specified at the start that is characterised by a constructionally simple structure and perfect tightness of the system. This object is achieved according to the invention in that the spout casing has a sealing ring that can be pressed in an air-tight manner against the seal of the casting tube on the face side. Thus, without introducing any inert gas either, the sealing ring brings about air-tight blocking of the sealing seat, especially as the negative pressure that occurs during casting automatically supports the pressing of the sealing ring against the seal of the casting tube. In this way it is possible to dispense with the supply of inert gas to the sealing seat or, if this is provided, to largely reduce it. In both cases considerable financial advantages arise from this. The sealing system is structurally very simple and is reliable in operation to a high degree.

In this sense it is particularly advantageous if a sheet metal ring preferably produced from sheet steel is used as a sealing ring, the radial width of which is matched to that of the seal of the casting tube.

Furthermore, the invention makes provision such that the sealing ring is positioned at a defined height of the spout casing which is calculated such that it guarantees total coverage of the seat surfaces of the casting tube and the spout casing in the assembled state.

It is advantageous for reasons relating to production and fitting if the seal of the casting tube is produced from fibrous ceramic material in the form of a conically moulded sealing casing which is provided with a face-side collar for enlarging the pressing surface of the sealing ring.

The sealing system according to the invention can also be used in devices the casting tube of which is provided with an inert gas feed opening out into the region of its seal.

A spout casing particularly suitable for the sealing system is characterised in that it is provided with a one- or multiple-part sheet metal jacket to which holders for the sealing ring are applied arranged distributed around the perimeter. Since it is in any case normal to use spout casings covered in sheet metal, the holders are preferably welded directly onto the existing sheet metal jacket in the form of sheet metal straps. According to the invention the sealing ring is fastened to the sheet metal straps with detachable connection means which can be screwed into the sheet metal straps or are driven into bore holes in the sheet metal straps as bolts or pins.

In the following the invention will be described in more detail using an exemplary embodiment with reference to the drawings. These show as follows:

Fig. 1 a longitudinal section of a partially shown slide gate comprising a sealing system according to the invention with a spout casing and a casting tube;

Fig. 2 a detail A of the spout casing in a view in the direction of the arrow B according to Fig. 2;

Fig. 3 a partial longitudinal section of the spout casing according to

Fig. 1 ;

Fig. 4 a top view of a sealing ring for the spout casing according to

Fig. 3; and

Fig. 5 a section of the sealing ring according to Fig. 4.

The slide gate 20 shown in Fig. 1 on the spout of a metallurgical vessel (not detailed) which can be, for example, a ladle filled with molten steel, comprises a housing 21 that can be fastened to the vessel and a slide unit 22 into which at least one refractory closure plate 23, 24 can respectively be inserted by means of the indicated centring elements 26. By shifting this slide unit 22 these closure plates 23, 24 are shifted towards one another by means of a drive and by means of the arrangement of flow openings 5 in the same opening takes place - as shown - or closing of the slide gate 20 in a conventional manner. In the latter are moreover a refractory casing 27 shown partially projecting into the vessel and adjoining beneath the closure plate 24 in the slide unit is a refractory spout casing 1 which is held in the slide unit 22 by means of a detachable fastening element 25 which can be, for example, a bayonet ring. In principle however the spout casing 1 could also be connected to the closure plate 24 as one unit.

Advantageously the spout casing 1 is formed tapering downwards conically on the outside and has in the upper part a collar V which serves as a contact surface in the bayonet ring. Pressed tightly against this spout casing 1 by means of an apparatus (not detailed) is a refractory casting tube 3 which is also called a ladle shroud and generally plunges into the molten steel of a distributor vessel located beneath the slide gate so that the molten steel poured in a controlled manner into the latter from the vessel is protected from the ambient air. This casting tube 3 is provided with an upper end 4 extending conically on the inside, and like the spout casing 1 , is provided with a through boring 5a or 5b.

The spout casing 1 is covered by a one- or multiple-part sheet metal jacket 6 the conical part 7 of which is pressed against a casing-like seal 8 preferably produced from a fibrous ceramic material with a collar 9 lying on the face side of the casting tube 3' at the top. This seal 8 is inserted, accurately fitting, into the casting tube 3. According to the invention the sealing seat formed by the sheet metal jacket 6 of the spout casing 1 and that formed by the seal 8 is additionally sealed with a sealing ring 1 1. This sealing ring 1 1 advantageously produced from sheet steel is positioned in a holder 12 of the sheet metal jacket 6 and is pressed against the collar 9 of the seal 8 of the casting tube. It thus provides together with the seal 8 double sealing of the formed sealing seat. The holder 12 and the fastening means for the sealing ring 1 1 are illustrated in Fig. 2 to Fig. 5. The holder 12 is formed by a number of, for example three, straps 14 made of sheet steel arranged distributed around the perimeter, which are welded onto the sheet metal jacket 6 on the inside. The straps 14 have receiving bore holes 15 for the fastening means of the sealing ring.

In addition, within the framework of the invention these straps 14 are dimensioned such that they form together with the spout casing 1 an outside diameter D1 which has dimensions equal to or smaller than the inside diameter 25' of the bayonet ring 25 and so the spout casing 1 can be inserted into the bayonet ring 25.

In the exemplary embodiment described holding bolts or pins 16 are provided as fastening means. These are welded into the sealing ring 11 and passed into the receiving bore holes 15 of the straps 14 so that they position the sealing ring 1 1 in the fitting position suitable for even pressing. The pressing force is primarily applied by the pressed on casting tube 3, but during casting it is increased according to the invention by a pressure difference P1 minus P2 then being produced between the pressure P1 of the surrounding area and pressure P2 in the interior of the passage opening 5b which supports the pressing of the sealing ring 11 against the seal 8 of the casting tube when pouring off molten metal.

The interaction of the seal 8 with the collar 9 and the sealing ring 1 1 thus enables sealing of the sealing seat that automatically strengthens when casting. Ambient air and so oxygen is thus prevented from penetrating into the molten metal through the sealing seat and impairing the quality of the molten metal. In this way a reliably operating sealing system is produced that makes the otherwise required supply of inert gas in order to establish a counter-pressure neutralising the suction effect unnecessary.

The sealing system according to the invention is structurally simple, reliable and financially advantageous, in particular with regard to the otherwise high operating costs associated with the consumption of the expensive inert gas.

Within the framework of the invention it is also possible, in order to fasten the sealing ring 11 in the holders 14, to use instead of the holding pins 16 connection elements which can be screwed into the bore holes 15 of the holders 14. Both fastening possibilities make it possible to fit the sealing ring 1 1 in the spout casing 1 when the latter is already fitted in the metallurgical vessel or the slide gate 20 fastened to the latter. The arrangement of the holders 14 in the spout casing 1 defines the installation height of the sealing ring. In practice this is chosen such that it guarantees full coverage of its seat surfaces according to the dimensions of the spout casing and the casting tube.

The sealing system according to the invention can also be used in conventional devices with an inert gas supply. In this case the gas supply is restricted to a minimum or optionally it is totally stopped. Needless to say the invention could also be demonstrated by other configurations. Thus, for example, the sealing ring 1 could be formed like a frame in order to increase stability, instead of these straps 14 a ring or similar surrounding the spout casing 1 could also be provided. The sealing ring 11 could also only strike the holder 12 for the purpose of positioning, but not be fastened to the latter.

Those sealing system according to the invention could also be applied for other devices respective closure systems on the spout of metallurgical vessels, like for instance for a stopper rod, a tundish slide gate, a metering nozzle, a nozzle change system or the like. Thereby the casting tube could be used as a submerged nozzle, which would for instance be submergeab!e into the molten metal in a casting mould.