Sliding closure for a metallurgical vessel, preferably a distributor vessel for a continuous casting facility

Slide closure for a metallurgical vessel, with two compensation units I and II for equalizing overloads, which may result from the thermal extension and spreading of the fire-proof closure plate thicknesses conditional on manufacturing, and/or from the upper inner shell, wherein the inner shell can also be reduced during operation. The compensation unit I consists of a spring arrangement with fastening screws which can be moved away between the housing and a cover of the housing. The compensation unit II consists, for its part, of a spring arrangement with an insertion frame pressing against the lower closure plate, which insertion frame is fixed to the bottom of the housing with fastening screws.

FIELD OF THE INVENTION

The invention relates to a slide closure for a metallurgical vessel, preferably a tundish for a strand casting system, with a housing that can be fastened onto the bottom of the vessel, an upper closure plate arranged in a cover of the housing, a lower closure plate and a central closure plate that can be longitudinally displaced between the upper and lower closure plates, and wherein the upper, lower and central closure plates are tensioned against one another with spring arrangements extending between the housing and the cover.

BACKGROUND OF THE INVENTION

Slide closures of this type are known in advance, for example from document EP 0 891 829. They are characterized in that, with them, the flow restriction or closing of the outlet is caused by the longitudinal movement of the slide plate. They thus serve in particular as a positioning member for controlled casting of the quantity of molten material from the metallurgical vessel.

For uninterrupted functioning of the slide closure, the plate tension is set such that it ensures both the free movability of the slide plate and the tightness of the slide closure required to prevent air from being sucked in. However, in operation, plate tension is subjected to additional stresses which result especially due to the thermal extension of the fire-proof plates. There are also stresses due to the likewise fire-proof upper inner shell in the vessel due to its thermal extension or reduction.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the invention is to produce a slide closure of the type named at the outset which absorbs, in optimal manner, the operational stresses of the plate tensioning due to the thermal extension of the closure plates and/or the extension or reduction of the upper inner shell.

This object is achieved according to the invention by providing a slide closure for a metallurgical vessel having a sleeve, with a housing fastenable to a bottom of the vessel and having a cover and an insertion frame, an upper closure plate in the cover of the housing, a lower closure plate in the insertion frame of the housing, and a central, displaceable closure plate longitudinally displaceable between the upper closure plate and the lower closure plate. The slide closure also includes a first compensation unit for tensioning the upper, lower and displaceable closure plates against one another and which includes a first set of spring arrangements that act on a tensile load between the cover and the housing, and a second compensation unit for pressing the upper, lower and displaceable closure plates against the sleeve and which includes a second set of spring arrangements that press the insertion frame in a direction toward the lower closure plate.

An optimal absorption of the fire-proof extensions can be achieved with this first compensation unit with spring arrangements for tightening the closure plates against one another, as well as this second compensation unit with spring arrangements for tightening the closure plates against the upper inner shell with an additional insertion frame, adjustable in the housing, which frame can be pressed against the lower closure plate.

By making the two compensation units interact with one another, both overloads due to the thermal extension of the fire-proof plates and also due to the extension or reduction of the fire-proof inner sleeve are minimized. Unlike the slide closure according to EP 0 891 829, such overloads are thus not limited initially by the rigidity of the fire-proof parts and the metallic slide housing. This is advantageous for the operability or the lifespan of the fire-proof parts of the slide closure.

The invention provides that the spring arrangement of the first compensation unit is composed of plate springs, the pretension of which can be set preferably using a stroke limiting stop of the fastening screws. The plate tensioning can thus be adapted to a broad range of extension of the fire-proof parts which results for thermal reasons or spreading of the fire-proof closure plate thicknesses conditional on manufacturing. The starting pretension of the springs can also be set, in precise and repeatable manner, with the stroke limiting stop.

In so doing, it is expedient if the plate springs transmit the spring stroke via swivel pins, the guides of which are provided with inserts. Wear of these parts is minimized as a result.

The invention also provides that the insertion frame of the second compensation unit is fixed on the bottom of the housing by means of fastening screws arranged in pairs on both sides of the outlet, with plate springs inserted between the screw head thereof and the insertion frame, which springs form the spring arrangement of the second compensation unit. In this way, a uniform load of the insertion frame and thus the lower closure plate can be achieved using means which are simple in design.

In order to ensure that the lower closure plate abuts tightly against the insertion frame satisfactorily, it is expedient to provide a sealing element comprising the outlet between the insertion frame and the housing, which element is inserted preferably in a groove in the housing and/or in the insertion frame.

The slide closure is advantageously provided with a replaceable casting tube which is pressed against the lower closure plate with spring-loaded pressing elements. The pressing elements are expediently arranged such that they are effective independently of the two compensation units of the slide closure. They thus remain operational in all operational phases, both with and without the casting tube.

DETAILED DESCRIPTION OF THE INVENTION

The slide closure according toFIG.1can be mounted on the outlet of a metallurgical vessel. The vessel is designed preferably as a tundish of a strand casting system, wherein the slide closure serves to regulate the quantity of molten material supplied to the strand casting ingot mould during the casting process. A casting tube3arranged on the bottom of the slide closure makes possible a covered casting of the molten metal into the ingot. However, this slide closure could also be used on a socket, a tap of a converter or the like.

The slide closure according toFIG.1andFIG.2comprises a housing4with a seal4′ arranged all around its upper end surface, in order that it is sealed in encircling manner on its top, at the vessel. Fixed, fire-proof closure plates5,6and a slider plate8(also referred to as a movable or displaceable closure plate), which can be moved back and forth therebetween by a drive mechanism7, can be inserted in the housing4, with the longitudinal movement of which an opening, restricting or closing of the outlet9(which is inside of an upper inner sleeve or sleeve1) is brought about. The upper closure plate5is arranged in a cover11of the housing4, rotatably housed about an axis10, whereas the lower closure plate6is fixed in an insertion frame25of the housing4and the movable closure plate8is fixed in a metal frame12coupled to the drive mechanism7. The casting tube3is pressed against the lower closure plate6with spring-loaded rockers33(also referred to as pressing elements herein). The housing4has supports13projecting on the top which abut against the outer steel casing of the tundish2when in operation.

As illustrated inFIG.3, a spring arrangement23has a base16guided in the housing4with a screw thread17and a crossways bolt18, about which a swivel pin20provided with a screw19can be swivelled, wherein the swivel pin20is guided into a recess21of the cover11and is screwed into a nut22above the cover11. In order to make possible access to the closure plates5,6and8, the nuts22can be loosened and the swivel pins20swivelled out of the recesses21of the cover11. The swivel pins20are provided with a stroke limiting stop20awith which the initial pre-stressing of the plate springs23′ acting on tensile load can be set in precise and repeatable manner Inserts24in the cover11are allocated to the nuts22of the fastening screws15a-15d, which inserts minimize wear as a consequence of the frequent assembly and disassembly of the screw connections during operation.

During operation, the nuts22are screwed so far onto the swivel pins20that the closure plates of the slide closure lying between the insertion frame25and the cover11are tensioned against one another with the respectively provided contact pressure. This contact pressure is such that, during operation, it ensures the uninterrupted movability of the slider plate8when the slide closure is fully impermeable to metal or gas from the outside.

During operation, the fire-proof closure plates5,6,8experience a dispersive mechanical extension of up to 3 millimetres due to heating or manufacturing tolerances, whereby plate tensioning is subjected to an additional stress. According to the invention, this is compensated by a first compensation unit I, because the plate springs23′ of the spring arrangement23more or less yield due to the additional stress. The stress compensation is very uniformly distributed over the closure plates in effective manner due to the paired arrangement of the fastening screws15ato15don both sides of the outlet1.

According toFIG.4andFIG.5, an insertion frame25with a spring arrangement30is arranged on the bottom of the housing4for tensioning the closure plates5,6,8against the upper inner shell1of the outlet. This additional insertion frame25is fixed to the housing4with fastening screws26arranged in pairs on both sides of the outlet.

For its part, the spring arrangement30consists of plate springs30′ which are inserted between the screw head28of the fastening screws26and the insertion frame25and have the function of pressing the insertion frame25against the lower closure plate6abutting against same, and thus tensioning the three closure plates5,6,8together against the upper inner shell1of the outlet.

The additional stress caused by an extension or reduction of the inner shell1is compensated with this second compensation unit II formed according to the invention, by the plate springs30′ more or less yielding due to this stress. It is advantageous if these plate springs30′ are produced such that they are provided with a steep characteristic curve in respect of its stroke in relation to the spring force, in order to bring about a relatively high change in force with little lift. This is matched to the corresponding characteristic curves of the plate springs23′ of the compensation unit I, in order that an optimal tensioning is always achieved. In so doing it is intended to be avoided that, depending on the position of the movable closure plate8, a tipping of the closure plates could take place, wherein this could occur due to an external application of force primarily through the casting tube3.

Furthermore, to improve the support between the housing4and the insertion frame25, a last, comprehensive sealing element31in a groove32is approximately half in the housing4and approximately half in the insertion frame25. A labyrinth effect is thus achieved which additionally improves the tightness. The groove could also be designed only in the housing or in the insertion frame.

FIG.6shows, schematically, the arrangement of the two compensation units I and II in the slide closure. The first compensation unit I is formed by spring arrangements23between the cover11and the housing4acting on tensile load for flexibly tensioning the closure plates5,6,8, because the second compensation unit II is effective due to the spring arrangements30between the insertion frame25and the housing4acting on pressure for tensioning the closure plates5,6,8against the inner shell1.

These compensation units can be set independently of one another and are also effective independently of one another, with the result that they can carry out their function both individually and also in combination with one another. As a result, they protect the fire-proof parts of the slide closure against overloads which can result from thermal extension and spreading of the fire-proof closure plate thicknesses conditional on manufacturing and/or of the upper inner shell, wherein the inner shell can also be reduced in operation.

Also, a choice is made to fix the central slider plate8in its metal frame12with a clamping device34such that the function of the compensation units I and II is not impaired by the arrangement thereof in the housing4.

The clamping device34according toFIG.7is composed of a clamping jaw38which can be adjusted against the closure plate8in the metal frame12, two adjusting elements35,36arranged on both sides of the central axis M of the slider plate8, as well as a threaded spindle37abutting against the adjusting elements. The threaded spindle37is rotatably housed transverse to the central axis M in the metal frame12and provided with thread sections going in opposite directions. By manually rotating this threaded spindle37, the adjusting elements35,36are adjusted outwards or inwards, symmetrically to one another, and by corresponding wedge surfaces35′,36′ in the adjusting elements35,36or the clamping jaw38, the latter is pressed against the closure plate8, with the result that a self-locking wedging is created in order that these do not become loose during operation.

The invention is displayed sufficiently using the above explained embodiment example. Self-evidently, other variants can also be provided. Other springs, such as helical springs or the like, could thus also be used instead of these plate springs23′,30′.