CA1337500C - Method and apparatus for removing a blockage from the pore opening of a molten metal containment vessel - Google Patents

Abstract

Apparatus is provided for removing or disrupting a blockage from the pour opening of a molten metal containment vessel. The vessel has an elongated conduit extending from the pour opening outwardly of the vessel for passage of molten metal from the vessel via the pour opening and the conduit to an outlet of the conduit: and the apparatus comprises a gas conduit connectible to a supply of pressurised gas (e.g. oxygen or an inert gas) and extending into the molten metal conduit through the outlet of said conduit to provide a barrel which is secured in said conduit and aimed at the pour opening; and a projectile loaded in the barrel and, on admission of pressurised gas to the gas conduit, propellable towards the pour opening to impact on any blockage therein. The projectile may comprise a leading end portion comprising material adapted to generate a chemical reaction to facilitate removal or disruption of the blockage.

Description

This invention concerns improvements relating to metal teeming.
Typically nowadays, molten metals are teemed from vessels such as ladles via outlets in or adjacent their bottoms. Teeming through a bottom pour opening is care of a teeming control means. Stopper rods and sliding gate valves are employed as teeming control means.
Where a sliding gate valve is used, it is placed at the downstream or outer end of the bottom pour opening.
The latter is provided by a passage through a well or nozzle block suitably installed in the refractory lining of the vessel.
In a gate valve controlled system, a particulate well filler is often put in the passage defining the pour opening before the vessel is filled with molten metal.
Should the well filler be omitted, molten metal will enter the passage. The melt may reside in the vessel for a relatively lengthy period of time before teeming is started. During this time components of the melt can solidify on the wall of the well or nozzle block passage, partly or fully occluding the passage. It is to prevent such an occurrence that metal producers resort to well fillers. Being a particulate material such as a refractory sand, a well filler should discharge from the passage as -2- t 3375GO
soon as the valve is opened for the first time, leaving the way clear for the melt to exit from the vessel through the valve.
Unfortunately, the well filler will not always discharge as desired. Due to the high temperature of the melt in contact with the top part of the filler, the latter may sinter into a hard skin or skull which blocks the entrance to the passage, so teeming is prevented. The skull must obviously be removed in some way. However, this is not easy because the skull is at the bottom of a bath of molten metal. The method often adopted for attacking a well skull involves introducing a lance pipe into the pouring orifice and oxygen lancing.
An object of the present invention is to devise an improved apparatus and method for attacking a blockage preparatory to teeming molten metal from a vessel; the invention may or may not be used in association with oxygen lancing.
The invention provides apparatus adapted for use in removing or disrupting a blockage from the pour opening of a molten metal containment vessel, which vessel has an elongated conduit extending from the pour opening outwardly of the vessel for passage of molten metal from the vessel vla the pour opening and the conduit to an outlet of the conduit: the apparatus comprising (a) a gas conduit _3_ 1 337500 connectible to a supply of pressurised gas (e.g. oxygen or an inert gas) and extending into the molten metal conduit through the outlet of said conduit to provide a barrel which is secured in said conduit and aimed at the pour opening; and (b) a projectile loaded in the barrel and, on admission of pressurised gas to the gas conduit, propellable towards the pour opening to impact on any blockage therein.
The projectile may comprise material (e.g. iron or steel wool, magnesium or solid fuel propellants) adapted to generate a chemical reaction to facilitate removal or disruption of the blockage.
The invention also provides apparatus adapted for use in removing or disrupting a blockage from the pour opening of a molten metal containment vessel, which vessel has an elongated conduit extending from the pour opening outwardly of the vessel for passage of molten metal from the vessel via the pour opening: the apparatus comprising (a) a gas conduit connectible to a supply of pressurised gas (e.g.
oxygen or an inert gas) and providing a barrel secured in the molten metal conduit and aimed at the pour opening;
and (b) a projectile loaded in the barrel and, on admission of pressurised gas to the gas conduit, propellable towards the pour opening to impact on any blockage therein; a leading end portion of the projectile comprising a metal -_4_ l 3 3 7 5 o O
(e.g. iron or steel) housing containing a reactive material which burns on impact with a blockage to facilitate removal or disruption of the blockage, the reactive material consisting essentially of iron or steel wool and being free of magnesium.
Surprisingly we have found that in the presence of oxygen, iron or steel wool will ignite very readily in the absence of any more reactive material such as magnesium, but the reliability of the ignition of the wool may be improved by the provision of percussion means e.g. one or more flints operable on impact with a blockage.
In embodiments of the invention the projectile is for example substantially tubular and is not totally expelled from the barrel in the operation of the apparatus, thus permitting the continuing passage of inert gas or lancing oxygen to the region of the blockage to facilitate its removal or disruption. The barrel extends, for example, from adjacent the outlet of the molten metal conduit for at least a major portion of the length of the molten metal conduit.
The length of residence of the projectile in the barrel ensures that, as the leading end portion of the projectile is consumed by burning, the projectile is advanced by the pressurised gas to remain in contact with the blockage, thus for example prolonging the time for burning of the iron or steel wool in contact with the blockage, or the time for oxygen lancing or inert gas flow into the region of the blockage. Also there is ample barrel length for an adequate velocity to be attained by the projectile before impact with the blockage.
The invention also comprehends projectile per se and method aspects.
A method for removing or disrupting a blockage using apparatus according to the invention may be carried out as a precautionary measure, whether or not a blockage has actually formed.
There now follows a description, to be read with reference to the accompanying drawings of apparatus embodying the invention. This description which is also illustrative of projectile per se and method aspects of the invention is given by way of example only and not by way of limitation of the invention.
In the accompanying drawings:
Fig. 1 is a longitudinal cross section showing part of a vessel, its lining, a sliding gate valve and a first apparatus embodying the invention;
Fig. 2 is an enlarged, part-sectional view of parts of the apparatus;
Figs. 3 and 4 are fragmentary enlarged sectional views of alternative end portions of the apparatus;

- - --Fig. 5 shows in longitudinal cross section a second apparatus embodying the invention;
Fig. 6 illustrates an alternative connection arrangement which may be employed;
Fig. 7 is a longitudinal cross section of a third apparatus embodying the invention;
Fig. 8 is a cross section at right angles of a tip assembly also shown in Fig. 7;
Fig. 9 is a longitudinal cross section of part of a fourth apparatus embodying the invention; and Fig. 10 is a cross section at right angles to Fig. 9.
The apparatus embodying the invention is adapted for use in removing or disrupting a blockage from the pour opening 11 of a bottom pour molten metal containment vessel 10 such as a ladle. The pour opening 11 is provided by a pour passage 13 in a three-piece well block 12, and the orifice in a stationary orifice plate 18 mounted immediately below the well block 12. The block 12 is mounted in the refractory lining of the vessel 10.
To control teeming from the vessel, a sliding gate valve 16 is provided having a lower orifice plate 20 in sliding contact with the stationary orifice plate 18. The gate valve is a well known apparatus and will not be described in detail.

1 3375~J

Means is provided, as is known, for displacing the lower plate relative to its companion for throttling or arresting the teeming of molten metal from the vessel. The valve 16 shown in Fig. 1 has a collector nozzle 21 undermounted thereon, its bore forming part of an elongated conduit extending downwardly from the underside of the plate 18 for teeming of molten metal from the vessel via the pour opening 11, the orifice plate 20, and the nozzle 21 to an outlet 23 of the nozzle 21.
In normal practice, the valve 16 is first closed by displacing the sliding plate 20 laterally to place its orifice out of registry with the orifice in the upper plate 18; and thereafter the vessel 10 is filled with molten metal. Subsequently, the melt is teemed from the vessel into a tundish or a mould, for instance of a continuous caster. It will be appreciated that melt could enter the pour passage 13 (if the latter is unfilled). In the course of pre-teeming residence, especially in lengthy period of residence, solidification of the molten metal in the pour passage could happen, blocking the passage. To prevent this, a refractory particulate well filler is placed in the pour passage 13 before the vessel is filled, so that the melt cannot enter the passage before the valve 16 is opened. When the valve is opened to commence a teem, the well filler should run out of the passage and valve ahead of the melt.
Often, however, the top of the well filler will form a solid crust, due to sintering in contact with the high temperature melt. The crust, skin or skull 22 is schematically indicated in Fig. 1; its precise position will depend to a degree on the level of filling of the bottom pour opening so it will not necessarily be located where shown in Fig. 1. The thickness and thus the strength of the skull will depend inter alia upon the pre-teeming residence time and cannot be usefully quantified.Its effect, however, is significant for it can actually prevent teeming of the molten metal.
To overcome the skulling problem, apparatus embodying the invention is used to remove or disrupt the blockage caused by the skull.
The apparatus 30 is lodged in the collector nozzle 21 in the arrangement shown in Fig. 1. Apparatus 30 comprises a straight tubular barrel 31 which extends into collector nozzle 21 through the outlet 23 of the nozzle 21;
and the barrel 31 is secured in the nozzle 21 so that it is aimed at the pour opening 11. A tubular projectile 32 (Fig. 2) is telescopically loaded in the barrel and pneumatically propellable therefrom towards the pour opening 11 to impact on any blockage therein. The barrel 31 is e.g. made of stainless steel seamless tubing and the g projectile of iron or steel tubing. The clearance between the inside of the barrel 31 and the outside of the projectile 32 is such as to ensure the latter is freely movable lengthwise of the barrel. However, it is kept to a minimum to cut down gas losses, since gas under pressure is fed to the barrel 31 for propelling the projectile at the skull.
The position and length of the barrel 31 are such that it extends upwardly from the outlet 23 of the nozzle 21 for almost the entire length of the elongated molten metal conduit provided by the nozzle 21 and the orifice in the plate 20, the barrel terminating just below the plate 18 so that it does not interfere with the sliding movement of the plate 20 relative to the stationary plate 18. The position and length of the projectile 32 relative to the barrel 31 are such that the projectile is not totally expelled from the barrel 31 in its propulsion to impact on the skull.
Still referring to Figs. 1 and 2, the projectile 32 is closed at its leading end and open at its trailing end.
The end closure is a plug 33 made of a low melting point material, e.g. aluminium or lead. It is meant to melt after firing the projectile 32 at the skull, so that gas can be ejected for such can assist in dispersal of the skull.

The barrel 31 forms part of a gas conduit which is connected to a supply 48 of pressurised gas (e.g. oxygen or an inert gas). The gas conduit also comprises a gas pipe 36 and the barrel 31 is appropriately adapted at its lower end 34 for connection to a union or inlet fitting 35 whereby the barrel is connectible to the gas pipe 36. As shown in Fig. 2, end 34 may be screw threaded. A
dislodgeable cap 38 is fitted to the leading end of the barrel, to prevent dirt or particulate matter from entering and possibly immobilising the projectile 32 in the barrel.
The cap 38 is fitted such that it can be pushed off the barrel when the projectile 32 is fired toward the skull.
Means is provided for locating and securing the barrel 31 in place in the nozzle 21. The holding means comprises at least one set 40, and preferably more than one set, of outwardly prjecting legs 42 which engage the wall 43 of the nozzle 21. The set of legs take the form of a resilient anchor, the legs 42 being sprung outwardly but displaceable inwardly when the barrel is pushed upwardly into the nozzle 21. As will be noted from the drawings, the legs 42 point downwardly and, due to their outward bias, they will jam more tightly against the wall 43 if the barrel is displaced downwardly. Accordingly, the legs 42 will counteract recoil of the barrel 31 when the projectile 32 is propelled therefrom.

It will be appreciated that the set or sets of legs 42 can hold the barrel central in the passage 43 whereby the projectile 32 is aimed axially along the teeming path at a well skull which may develop.
There will usually be three or more legs 42 per set 40 thereof.
Means can be provided for releasably holding the legs closed to assist installation of the barrel 31 in its proper position.
For example, the legs 42 could be held closed until released by pulling on a draw cord or the like, not shown.
Recognising, however, that the passage in which the barrel will be inserted will ordinarily be hot, means to hold the legs closed temporarily could comprise a rubber ring 44 -see Fig. 2. Such a ring 44 will enable the user to install the barrel 31 properly before the ring softens in the heat and releases the legs.
In the arrangement shown in Fig. 1, there is just one set 40 of legs 42. A locating ring 45 clamped around the lower end portion of the nozzle 21 acts in conjunction with the legs to centralise and aim the barrel.

Desirably, the projectile 32 is positively retained in the barrel 31 for ease of shipping, storage and use.
Moreover, it may be desirable to provide retaining means _ 1 337500 such that the projectiles are all set back a consistent distance from the capped ends of their barrels 31. Such a retaining means is shown in Fig. 2 at 46. As shown, the retaining means is a disc spring washer, frictionally held in the barrel, on which the projectile 32 rests.
The gas pipe 36 is connected to the pressurised gas supply 48 via a gas valve 50 which is operable for suddenly applying pressurised gas to the inlet end of the barrel 31.
Control means, not shown, may be provided to enable the user to select the length of time gas is fed to the apparatus 30. The control means can, for example, act upon the valve 50. Excessive supply of gas into the melt, which might affect its chemistry or properties, can thus be avoided.
The apparatus set up generally as shown in Fig. 1 is used as follows, although during filling and up to the commencement of teeming the lower sliding plate 20 will be in its closed setting. To start a teem, the plate 20 will be moved to the position shown, whereby particulate well filler will run out of the pour passage 13 and through the valve 16. If there is no well skull, molten metal will then issue from the valve. Should no metal issue, the gas valve 50 will be switched whereby pressurised gas is suddenly applied to the lower end of the barrel 31, causing the projectile 32 to be fired forcibly at the passage-blocking skull 22. The impact of the projectile 32 on the skull may be enough to rupture the skull and allow the melt to pour normally from the vessel 10. Alternatively, the projectile may pierce the skull such that its tip will protrude into the melt. ~he plug 33 will then melt or burn away so that gas from the source 48 will enter the melt after traversing the gas pipe 36, the barrel 31 and the projectile 32 into the region of the skull. The gas will vigorously agitate the melt and the latter will facilitate removal or disruption of the already weakened skull; and if the gas is oxygen, lancing will take place.
Once molten metal is freed to enter the pour passage 13, it will melt, or maybe thrust the barrel 31 and projectile 32 downwards into the mould. In any event, these items 31, 32 will be disintegrated and flushed away with the initial flow of melt from the vessel each time teeming is initiated.
The projectile of Fig. 3 differs somewhat from that shown in Fig. 2. In particular, it includes a plurality of transverse gas outlets 52. The reason for these outlets 52 is this: in some cases a skull may become so thick that the projectile 32 will pierce but not shatter it. Transversely flowing, high-pressure gas ejected into the skull directly will, it is believed, successfully disperse the skull. As before, the end of the projectile 32 of Fig. 3 is closed by a plug 33. The outlets 52 may initially be closed by an internal or external sleeve of low melting point material. Such a sleeve could be integral with the plug 33. The purpose of such a sleeve is to prevent escape of gas as the projectile is being propelled at the skull, thus avoiding a restriction in the speed attainable by the projectile. As shown by way of example, there are four such ports 52 disposed along each of four axially-directed lines which are spaced at 90 intervals about the initially-closed end of the projectile 32.
Another projectile 32 having a plurality of transverse gas outlets 52 is shown in Fig. 4. In the arrangement shown in Fig. 4, the projectile 32 carries a ring 53 adjacent its end, the ring being either a jam fit on the projectile 32 or being welded or brazed thereto. In the ready position, the projectile 32 protrudes from the end of the barrel 31, and is thus retained by the ring 53 which abuts against the end of the barrel 31. The fitting of an external low-melting point sheath 55 to close the outlets 52 would be simple in this embodiment. The sheath 55 could, if desired, be made of a plastics material and might simply comprise a winding of plastics tape closing the outlets 52.

-The purpose of the ring 53 is to enlarge the projectile 32 adjacent its end, and in use can prevent the projectile 32 from passing straight through the skull and thereby separating itself from the barrel 31. Also, the ring can assist the projectile to weaken the skull preparatory to its dispersal.
Projectiles 32 having transverse outlets as described with reference to Figs. 3 and 4 can be employed not only in the embodiment of Fig. 1 but also the embodiment of Fig. 5 now to be described.
In Fig. 5, as in Fig. 1, the apparatus 30 is located inside a component associated with the gate valve 16. In this case, it is disposed, axially-aligned, inside an undermounted extended pour tube 58 which extends between the ladle and a tundish T. Tube 58 is held, by means not shown, to the nozzle 21. In this arrangement, the lower end of the barrel 31 is connected by a union 35 to a U-tube 59. The latter is connected to an upwardly-extending length of gas pipe 60 strapped to the pour tube and terminated in an elbow 62 to which the gas pipe 36 is connected. If preferred, the pipe 60 could be bent at its lower end so as to avoid the need for U-tube 59. To suit some working practices, the lower part of the barrel 32 and pipe 60 can be sheathed in a refractory cladding C. This cladding C protects the metalwork when the pour tube is immersed in melt e.g. already in the tundish T, before the apparatus 30 is activated to disperse a well skull.
The pipework 59, 60 of Fig. 5 could be replaced by use of the union 35' shown in Fig. 5 which can be of the same pattern as the union shown in Fig. 1. This is a side-entry union, for use when the bottom molten metal outlet of the pour tube 58 comprises lateral apertures 64, which permit access for a gas pipe to connect with the union.
The apparatus 130 of Figs. 7 and 8 is installed in the sliding gate valve assembly for example in a generally similar fashion to Fig. 1 or Fig. 5 but preferably as in Fig. 5.
The apparatus 130 comprises a seamless tubular barrel 131 of e.g. stainless steel and a steel or iron projectile comprising a trailing tubular body portion 133 and a leading tubular tip assembly 132 comprising material adapted to generate a chemical reaction to facilitate removal or disruption of the blockage.
The projectile is loaded in the barrel 131 and projects upwardly from the barrel 131. A flange 134 of the projectile rests on the upper end of the barrel 131.
The tip assembly 132 comprises a housing 137 which fits over the projecting portion of the tubular body portion 133 and is secured thereto by a pin 135 passing through corresponding apertures in the housing 137 and the body portion 133.
The barrel 131 is centrally located and secured in place in the sliding gate valve assembly, preferably in a submerged pouring tube generally as in Figure 5, or in a ladle shroud.
The housing 137 is for example of iron and filled with iron or steel wool 139 which extends from the upper end of the body portion 133 to the upper end of the housing 137.
The metal wool 139 is retained in position in the housing 137 by a pin 143 which extends through corresponding apertures in the housing 137 close to its upper end and through the upper end portion of the compacted metal wool.
A small bore axial gas passage 145 extends through the iron wool 139 and this is provided by winding the wool around a thin rod which is used to force the wool compact into the housing 137, the rod then being withdrawn to leave the gas passage 145.
In the operation of the apparatus, the barrel 131 is connected to a supply of oxygen via a gas valve (not shown), and the equipment may be used generally as described in relation to Fig. 1. The flange 134 prevents the projectile 133 passing through the skull and thereby becoming separated from the barrel 131 and the oxygen supply.

-18- l 3 3 7 5 0 o It will be realized oxygen also enters the gas passage 145 which extends through the metal wool 139, the pin 143 preventing the metal wool 139 being discharged out of the housing 137 by the gas pressure. The iron or steel wool ignites readily on contact with any surface heated to a dull red in the presence of oxygen without requiring the presence of a more readily combustible material such as magnesium; this is what happens in contact of the tip assembly 132 with the skull, the oxygen also causing the iron housing 137 itself to burn. This and the continuing supply of oxygen to the region of the skull melts or burns away the skull, with vigorous agitation also being provided by the continuing supply of oxygen which quickly breaks up the melting skull.
Steel rods may be included in the housing 137 in addition to the metal wool, in order to prolong the burning time.
In another embodiment a chemical fill, typically magnesium is used with or without arrangements for the supply of oxygen; where oxygen is not supplied an inert gas, e.g. argon, may be used instead to fire the projectile at the skull and the magnesium is ignited by the heat of the skull, and the temperature of the thermal reaction generated thereby is sufficient to melt or burn away the skull.

1 337~00 Again, chemicals which produce rapid gas emission on contact of the tip assembly with the skull can be used.
In another embodiment a solid fuel propellant is used, as a chemical fill producing rapid gas emissions.
The fill can be introduced into the casing in the form of capsules.
The embodiment of Figs. 9 and 10 resembles in many respects those of Figs. 7 and 8 and is described insofar as it differs therefrom.
The apparatus of Figs. 9 and 10 comprises a tip assembly 232 comprising a tubular hous~ng 237 which is secured to a tubular body portion 233. The housing 237 contains iron or steel wool 239 retained in position in the housing 237 by a pin 243. The metal wool may be provided as a leading portion 239a of a finer gauge generally above the pin 243, and a trailing portion 239b of a coarser gauge generally below the pin 243; the presence of the finer gauge wool 239a may facilitate the ignition of the body of metal wool 239 as a whole.
A leading end face of the casing 237 is drilled with three small symmetrically spaced holes 250 which extend obliquely upwardly and outwardly through the casing wall.
In each of the holes 250 is tightly fitted a flint 252 which extends obliquely upwardly and outwardly of the end face of the casing 237. The flints 252 are e.g. of the kind used in gas lighters and smokers' lighters. The flints 252 may be covered by a striker cap 253 cooperable therewith and which fits over the leading end portion of the casing 237 but the striker cap may not be necessary in all cases.
In the absence of the striker cap 253, when the projecting flints 252 impact on the blockage they are apparently driven into their holes 250 and produce sparks which facilitate ignition of the metal wool 239.
If the blockage is, for example, liable to be of a spongy nature then it may be preferred to use the striker cap 253 to provide a hard surface of impact for the flints 252.
It will be realized that the flints 252 can be used also to initiate reaction of reactive materials other than the metal wool, including those referred to hereinabove.

Claims (26)

1. Apparatus arranged to remove or disrupt a blockage from the pour opening of a molten metal containment vessel, which vessel has an elongated conduit extending from the pour opening outwardly of the vessel for passage of molten metal from the vessel via the pour opening and the conduit to an outlet of the conduit; the apparatus comprising (a) a gas conduit connectible to a supply of pressurised gas and providing a barrel secured in the molten metal conduit and aimed at the pour opening; and (b) a projectile loaded in the barrel and, on admission of pressurised gas to the gas conduit, propellable towards the pour opening to impact on any blockage therein; a leading end portion of the projectile comprising a metal housing containing a reactive material which burns on impact with a blockage to facilitate removal or disruption of the blockage, the reactive material consisting essentially of iron or steel wool and being free of magnesium.

2. Apparatus according to claim 1, wherein the housing of the leading end portion of the projectile is of iron or steel.

3. Apparatus according to claim 1 or claim 2, wherein the leading end portion of the projectile is provided with percussion means to facilitate initiation of reaction on impact with any blockage.

4. Apparatus according to claim 3, wherein the percussion means comprises one or more flints.

5. Apparatus according to claim 4, wherein the percussion means comprises a leading striker member co-operable with the flint(s).

6. Apparatus according to any one of claims 1, 2 or 4, wherein steel rods are also included in the housing of the leading end portion of the projectile to prolong the burning time.

7. Apparatus according to any one of claims 1, 2, or 4, wherein the iron or steel wool is provided as a leading portion of a finer gauge and a trailing portion of a coarser gauge.

8. Apparatus according to any one of claims 1, 2, or 4, wherein the projectile is substantially tubular, being open at its trailing end for communication with the interior of the barrel; and the projectile is not totally expelled from the barrel in the operation of the apparatus.

9. Apparatus according to claim 8, wherein the barrel extends from adjacent the outlet of the molten metal conduit for at least a major portion of the length of the molten metal conduit.

10. Apparatus according to claim 9, wherein the gas conduit extends into the molten metal conduit through the outlet of said conduit.

11. Apparatus according to any one of claims 1, 2 or 10, wherein the molten metal conduit comprises a pour tube extending between the ladle and a tundish, and wherein for example the gas conduit enters the pour tube by way of a U-bend in the gas conduit.

12. A projectile adapted for use in apparatus according to claim 1, comprising a leading end portion which comprises a metal housing containing a reactive material consisting essentially of iron or steel wool and being free of magnesium.

13. A projectile according to claim 12, wherein said housing is of iron or steel.

14. A projectile according to claim 12 or claim 13, wherein its leading end portion is provided with percussion means to facilitate initiation of reaction on impact with any blockage.

15. A projectile according to claim 14, wherein the percussion means comprises one or more flints.

16. A projectile according to claim 15, comprising a leading striker member co-operable with the flints.

17. A projectile according to any one of claims 12, 13 or 16, wherein steel rods are also included in said housing.

18. A projectile according to claim 17, wherein the iron or steel wool is provided as a leading portion of a finer gauge and a trailing portion of a coarser gauge.

19. A projectile according to any one of claims 12, 13, or 18, comprising a tubular trailing body portion open at its trailing end.

20. A projectile according to claim 19, when loaded into the barrel.

21. A method for removing or disrupting a blockage from the pour opening of a molten metal containment vessel, wherein a projectile is impacted on the blockage by use of apparatus according to claim 1.

22. A method for removing or disrupting a blockage from the pour opening of a molten metal containment vessel, wherein a projectile is impacted on the blockage by use of apparatus according to claim 8, when gas flows from the barrel along the tubular projectile into the region of the blockage to facilitate removal or disruption of the blockage.

23. A method for removing or disrupting a blockage from the pour opening of a molten metal containment vessel wherein a projectile according to claim 12 is impacted on the blockage.

24. A method for removing or disrupting a blockage from the pour opening of a molten metal containment vessel wherein a tubular projectile according to claim 19 is impacted on the blockage, when gas flows along the tubular projectile into the region of the blockage.

25. A method of pouring molten metal, wherein a blockage is removed or disrupted by a method according to claim 21 or 22, and the barrel and projectile are disintegrated and flushed away with the initial flow of melt from the vessel.

26. A method according to claim 22 wherein the gas is oxygen.