Note: Descriptions are shown in the official language in which they were submitted.
-1- 1 337500
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
1 337500
--5--
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;
- - -
-
1 337500
--6--
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
--7--
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
1 337500
-8-
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
1 337500
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.
1 337500
--10--
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.
-11- 1 3 3 7 5 0 0
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
-12-
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-
1 337500
-13-
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
1 337500
-14-
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.
-
1 337500
-15-
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
1 337500
-16-
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
1 337500
-17-
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
--19--
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
1 337500
-20-
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.
