GB2235889A - Improvements in or relating to refractory monoblock stoppers - Google Patents

Abstract

A one piece ceramic stopper rod used to control the flow of molten metal exiting from a nozzle in a metal containing vessel, has a flared end portion (10) adapted to be received into a corresponding shaped tapered cup (9) in a stopper support (5) further providing at or near the flared portion a bearing surface for receiving means for ensuring in use a tight fit between the surface of the flared portion and the tapered cup. The embodiment shown employs a retaining plate (6) held in place by cotter pins (7, 7'), but other embodiments use a bayonet joint arrangement. <IMAGE>

Description

ImProvements in or relating to Refractorv Monoblock Stoppers This invention relates to refractory monoblock stoppers, i.e. one piece ceramic stopper rods commonly used to control the flow of molten metal exiting from a nozzle in a metal containing vessel, eg. tundish or ladle.

Typically, such stoppers consist of an elongated body having at the lower end a profile suitable for engagement in the throat of an exit nozzle thereby effecting the flow control, and at the upper end some form of connecting means to fasten the stopper onto an external lifting mechanism by which the flow is controlled.

Normally the connecting means involves fixing a metal hanger bolt into the stopper body by a thread form engaging either in a ceramic thread, or co-pressed metallic female threaded insert, within the stopper body. Other systems include a cross pin fastening or ceramic insert.

For example, our co-pending application GB-A-2 210 305 discloses a refractory monoblock stopper formed by isostatic pressure, having an end portion adapted to receive support means including a hanger bolt and a cross-pin, wherein the end portion has embodied in it heat-resistant metal bushing for receiving the cross-pin.

The specific design and materials used in these bushes, together with specialist tooling and manufacturing techniques, allow the bushes to spread evenly any point loads they receive onto the full wall thickness of the refractory, thus allowing the stopper to operate satisfactorily with much greater tolerance of deformities and other variables within the steel plant operation.

The prior art outlined above however suffers from the inherent disadvantage that a degree of pre-assembly is required to fix the hanger bolt into the stopper, particularly in effecting what seals may be necessary prior to the installation of the stopper and hanger bolt into the control mechanism.

In a typical operation the one piece ceramic stopper rod is removed from a protective packaging, and laid out an assembly bench, where the steel hanger bolts are fixed into place. The stopper is then transferred to a ready use storage area prior to assembly onto the operating mechanism.

At each stage of handling there is a risk of damage both to the upper fixing end, and the lower flow control surface, which could limit the effective performance of the stopper rod.

Additionally the steel hanger bolt and worn stopper rod must be retrieved after use, disassembled, and prepared for re-use. As the operating environment is very hostile with a risk of metal splashes and differential expansions, the precise thread forms normally employed need be subject to regular maintenance.

The object of the present invention is to obviate or mitigate the aforementioned problems.

A further object of the present invention is to provide a ready for use ceramic one piece stopper rod which can be pulled from its protective storage case and fixed directly onto the operating mechanism with a simple locking device well suited to the operational environment.

Accordingly, the invention provides a refractory monoblock stopper, having a flared portion at or near a first end thereof, said flared portion being adapted to be received into a corresponding tapered cup in a stopper support and having at or near said first end a bearing surface for receiving means for ensuring a tight fit between the surface of the flared portion and the tapered cup in use.

Preferably, the flared end portion forms a frustum and the tapered cup forms a corresponding frustum.

Preferably also, the bearing surface is adapted to receive securing means requiring no threaded couplings for retaining the stopper within the tapered cup.

Advantageously, said bearing surface is a flat end surface of said first end of said stopper upon which there may be superposed securing means comprising an oversize plate, of larger surface area than the abutting end surface at said flared end of the stopper, and a plurality of fasteners for securing the plate to the stopper support.

Conveniently such fasteners are in the form of retaining cotters contacting the plate to urge it into abutment with the bearing surface of the stopper and are so arranged as to evenly distribute loading through the plate onto said bearing surface.

Preferably, the stopper support is in the form of an arm mounted in an adjustable manner within means for allowing axial alignment of the stopper to the exit nozzle axis.

The present invention reduces the labour involvement in the set up of a stopper for operation, reduces the risk of physical damage, provides a means for inert gas injection couplings, and a simple fastening mechanism. At the end of the service life the used stopper rod can easily be removed from the operating mechanism, leaving the mechanism ready to receive a new component for subsequent re-use.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figs. l(a) to (e) show a cross section of a refractory monoblock stopper assembly, with a variety of alternative fixing systems according to the prior art; Fig. 2 shows a cross section of a first refractory monoblock stopper assembly, according to the present invention; Fig. 3 shows a partial view from the side of a second refractory monoblock stopper assembly where a monoblock stopper is held in contact with a stopper arm; Fig. 4 shows a cross-sectional view of the refractory monoblock stopper assembly of Fig. 3 rotated through 900; 90 ;; Fig. 5 shows a partial view from the side of an improved version of the refractory monoblock stopper assembly of Fig. 3 where a monoblock stopper is held contact with a stopper arm; Fig. 6 shows a partial cross-sectional view from the top of the refractory monoblock stopper assembly of Fig. 5; and Fig. 7 shows a part cross-sectional view from the side of the monoblock stopper assembly of Fig. 5 where a third monoblock stopper is held in contact with a stopper arm.

Referring to Fig. 2 there is shown a first embodiment of a monoblock stopper 11 according to the present invention. There is provided an operating mechanism 1, similar to that used in the prior art, positioned outwith a tundish shell 15. A height adjustment nut 2 is provided, allowing height adjustment of a stopper arm 5 on the operating mechanism 1. An arm locking nut 3 is also provided to fasten the stopper arm 5 onto the operating mechanism 1.

At the outer end of the stopper arm 5 is a tapered cup 9 suitable for receiving the stopper 11 having a matching flared upper end 10 such that the flared portion of the stopper 11 seats in a close fit within the cup 9.

The stopper 11 is retained within the tapered cup 9 by means of an oversize retaining plate 6, maintained in position on the stopper arm 5 by means of at least two cotter pins 7, 7'.

The cotter pins 7, 7' provide simple fixing means and allow easy removal of the plate 6 and stopper 11. For example, by removing pin 7' the plate 6 may be rotated about pin 7 to such a position as to allow installation or removal of stopper 11. This provides for extremely quick and simple replacement of worn stoppers.

A hole 16 is provided on plate 6 to allow insertion of an argon supply pipe 8 into an argon supply channel 12 in the stopper 11, for the purposes of excluding air as is common in the prior art.

A slot 4 on the stopper arm 5 allows longitudinal movement of the stopper arm 5 with respect to an upright in the operating mechanism 1, and therefore also allows axial alignment of the stopper 11 to the axis of an exit nozzle 14 of the tundish shell 15. This provides for accurate fitting of the stopper 11 and allows for efficient valve closing operation.

Referring to Figs. 3 and 4, there is provided a second embodiment of a monoblock stopper 11' according to the present invention. Like the stopper 11, the stopper 11' is retained within a cup 9' at the outer end of a stopper arm 5'. However, stopper 11' has a flared portion 10' near to a first end of the stopper 11' there further being provided at said end a substantially cylindrical portion 20' having a diameter slightly less than the internal diameter of a corresponding portion 21' in the stopper arm 5'. It has been found that the inclusion of these portions 20', 21' provide additional support but also imparts tolerance to vertical axis flexure arising during operation.

Further, the stopper 11' is retained in contact with the cup 9' by means of a reusable substantially annular retaining plate 6'. The plate 6' is retained by a bayonet type connection 18' comprising a pair of pins 19' extending on either sides of the plate 6' and a pair of corresponding slots 22' on either side of the cup 9' of the stopper arm 5' The bayonet connection 18' has the advantage over the cotter pins 7, 7' of no moving parts, while still providing the advantage of easy stopper 11' replacement.

Also, a can 23' is jigged around the inner surface of the flared portion 10'. This can 23' provides the required seating surface and angle for the flared portion 10' of the stopper 11', as well as resisting point loading.

Referring to Figs. 5, 6 and 7 there is provided an improved version of the second embodiment of the refractory monoblock stopper assembly, wherein the bayonet connection 18' may be secured by means of a pin 24' or a pair of pins 24' insertable through one of the slots 22' or both slots 22' so as to prevent the removal of the pins 19' from the slots 22'.

In summary, the present invention provides a simple assembly comprising a stopper support arm 5, 5' having a retaining cup-shaped aperture 9, 9' i.e. with a tapered profile, and a uniquely shaped ceramic stopper 11, 11' having a flared profile at the opposite end 10, 10' from a nose 17, 17' of the stopper 11, 11', the profile of the end 10, 10' matching exactly that of the retaining cup 9, 9' on the stopper arm 5, 5'. This arrangement is ideal for locating the stopper 11, 11' in position and avoiding misalignment in use due to distortion or other physical damage which can arise in typical mounting arrangements.

Its inherent simplicity provides for improved operational life and facilitates exchange of worn components in a short time.

Precision fabrication of the profiles may be provided by accurate pressing, machined exterior, or "canned" top section.

The invention also provides a unique stopper body 11, 11' which can be slimmer than earlier art due to the absence of a large bore to receive a hanger bolt, with associated sSv-i-ngs in weight, cost, and reduction in metal volume displaced, this being potentially critical on small tundish multi stopper operations.

Claims (9)

Claims

1. A refractory monoblock stopper having a flared portion at or near a first end thereof, said flared portion being adapted to be received into a corresponding tapered cup in a stopper support and having at or near said first end a bearing surface for receiving means for ensuring a tight fit between the surface of the flared portion and the tapered cup in use.

2. A refractory monoblock stopper as claimed in claim 1, wherein the flared portion forms a frustum and the tapered cup forms a corresponding frustum.

3. A refractory monoblock stopper as claimed in claim 1 or 2, wherein said bearing surface is a flat end surface of said first end of said stopper upon which there may be superposed securing means comprising an oversize plate, of larger surface area than the abutting end surface at said end of the stopper, and a plurality of fasteners for securing the plate to the stopper support.

4. A refractory monoblock stopper as claimed in claim 3, wherein said fasteners are in the form of retaining cotters contacting the plate to urge it into abutment with the bearing surface of the stopper and are so arranged as to evenly distribute loading through the plate onto said bearing surface.

5. A refractory monoblock stopper as claimed in claim 1 or 2, wherein said bearing surface is a flat end surface of said stopper upon which there may be superposed securing means comprising a substantially annular plate, and a plurality of fasteners for securing the plate to the stopper support wherein said fasteners are in the form of at least one pin extending from said annular plate said pin being engagable with a corresponding slot in said stopper arm so as to form a bayonet type connection.

6. A refractory monoblock stopper as claimed in any preceding claims, wherein said flared portion is provided near said first end of said stopper, there being provided at said first end a substantially cylindrical portion which is received into a corresponding substantially cylindrical portion in said tapered cup when said tapered portion is located in said tapered cup.

7. A refractory monoblock stopper as claimed in claim 6, wherein the outer diameter of said substantially cylindrical portion of said stopper is less than that of the corresponding cylindrical portion of said cup such that in use said cylindrical portion of said stopper provides support between said stopper and said support arm, but also imparts tolerance to allow flexure of the longitudinal axis of the stopper.

8. A refractory monoblock stopper as claimed in any preceding claims, wherein there is provided a jigged can around the tapered portion of the stopper so as to provide the required seating surface and angle, while also resisting any point loading.

9. A refractory monoblock stopper as described hereinbefore with reference to the accompanying drawings.