Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Ladle
This invention relates to ladles for molten metal, and particularly to
liners for such ladles.
Ladles for molten metal are generally in the form of a truncated cone
made of iron or steel having internal linings of refractory material.
Initially
the liner materials, namely silica, alumina and magnesite based materials,
were mixed with an inorganic binder to form a refractory layer which could
withstand the high pouring temperatures and corrosive slags of ferrous
metals. The materials were either hand rammed into place or poured/packed
around a form to produce the inside shape of the ladle.
One form of ladle for molten metal, known as a teapot ladle, is
distinguished by a spout, extending from the bottom of the ladle to its top
edge, or lip, thus ensuring the provision of clean metal to the mold from the
interior of the ladle.
Using traditional refractory practices, foundries can produce the spout
of the teapot design in many ways. For example a half round or flat
refractory tile can be embedded into the internal cylindrical sidewall of the
refractory liner. However, all conventional refractory materials used must be
preheated, at considerable cost, to avoid chilling the metal. and to prevent
thermal shock to the refractory.
In the early 1980's KALTEK shank ladle liners were
introduced. These are one-piece linings made of silica, alumina and
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magnesite, and are vacuum formed and bonded with an organic material such
as phenolic resin to make the product strong (for transportation purposes)
when cured. These liners are low density and low thermal conductivity and
are thus insulating by nature, compared to conventional refractory liners.
They do not last as long as conventional refractory liners, and thus the
material costs are greater. However, being easy to install without the need
for special equipment, insulating by nature, frequently changed out and not
requiring preheat, there are many advantages, such as lower labour and
energy costs, lower employee injury, better metal temperature control, lower
scrap rates and no pre-heat costs.
In use, a layer of coarse sand is poured into the bottom of an empty
ladle shell and the KALTEK liner is placed inside the shell on the bed
of sand and levelled with the top of the ladle shell. More sand is poured
between the liner and shell until a level slightly below the top of the liner
is
achieved. A capping material is then applied to the void below the top of the
liner to prevent the sand from coming out of the ladle during the pouring
when the ladle is tipped forward. The capping material can be any self
drying material such as aqueous sodium silicate mixed with sand. The
capping material is vented allowing gas from the organic binder to escape
when metal is poured into the ladle.
Upon the introduction of KALTEK liners, consideration was
given to the development for a teapot ladle of a KALTEK liner of
cylindrical or truncated cone shape having a pouring spout to serve as part of
a teapot ladle system.
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Initially it was proposed to use a straight/flat tile (dam or barrier plate)
embedded into the liner internal sidewall to form the spout. Such a proposal
is shown in Figure 1, with the tile 10 being embedded, with refractory
mortar, into grooves in the inner sidewall 11 of the liner 12, so as to define
a
spout 13, through which poured metal flows, in use. A similar liner for a
teapot ladle is shown in Figures 2 and 3 of U.S. Patent No. 4,330,107,
where again the flat tile is embedded in the sidewall of a KALTEK~
liner.
With the flat tile itself being of KALTEK material, it was
found that it did not last as long as required to justify its high cost before
it
broke.
Moreover, the KALTEK material was found to gas into the
metal contained in the liner because its organic components burn out on
contact with the high metal temperatures. In the walls (i.e. the body) of the
ladle lining, the resultant gases exit through the backing sand, causing no
problems. Unfortunately the dam or barrier plate is surrounded on both sides
with molten metal, causing excess hydrogen and nitrogen pickup in the metal
itself. This creates defects in the final castings.
Making the flat tile of conventional refractory/ceramic material was
never implemented as, although a longer life could be expected, it would be
of very high cost and would be expected to cause a chill effect on the metal
mentioned above.
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An alternative solution attempted was to use a half-round tile (dam or
barrier plate) embedded into the liner internal sidewall to form the spout.
Such a proposal is shown in Figure 2, with the tile 14 being embedded, with
refractory mortar, into grooves in the inner sidewall 11 of the liner 12 to
define a spout 15, through which metal flows, in use.
With the half-round tile being of conventional refractory/ceramic
material, it was found that it cracked due to `thermal stress' related to its
curved shape. Additionally it sometimes came loose from the grooves. Its
cost was however lower than a flat tile, because its shape allows it to be
smaller. It was never contemplated making the half-round tile of KALTEK
material, as this would have been expensive due to the need for
complex tooling. The KALTEK material would still gas into the
metal excessively and such a tile would not have been expected to have a life
any longer than a flat tile, perhaps shorter.
To overcome this problem of producing a KALTEK liner for a
teapot ladle, a solution was developed in 1987 which involved using a smaller
(less wide), flat, cast refractory or ceramic tile (dam or barrier plate) 16,
thus
decreasing the cost, fitted at the periphery of the circular section liner 17,
as
shown in Figure 3. In order not to close off the bottom opening of the spout
18 partly defined by the tile faster than the top, resulting in an inability
to
achieve cost, flow rate and thermal performance objectives, the circular
section liner had to be provided with an externally curved, outward hollow
extension 19 extending downwardly the whole length of the liner below the
upper lip.
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Insulating tiles, e.g. of KALTEK material, were not used in
this new design, because they did not possess the longevity required, and
because the organically bonded KALTEK material would gas
excessively.
Although this new design works well, with the tile being of lower cost
due to its smaller size, it suffers from the disadvantage that most foundry
ladles in which the liner would be set had to be modified to include room for
the extension 19. Most such ladles are of cylindrical cross-section with
various lip designs to fit their specific application or moulding line layout.
Modifying and rebalancing the ladle costs time and money and often results
in delays of product trials.
It has thus been appreciated that what is required is a teapot liner
which would fit into any foundry ladle shell without the need to modify it,
and an object of the invention is to provide such a liner, as well as a ladle
provided with such a liner.
According to a first aspect of the invention, there is provided a liner
for a ladle, the liner comprising a body of refractory material defining a
hollow interior, the body having a continuous sidewall bounding said hollow
interior, a lower closure floor and an open top, a barrier of refractory
material facing an interior surface of part of the sidewall and being spaced
inwardly therefrom in said hollow interior, the barrier extending from at or
near the open top of the body towards said lower closure floor to define, with
said facing part of said sidewall, a spout for discharging molten metal, in
use, from said interior of the ladle, the barrier having two longitudinal edge
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surfaces, two facing inner portions of the sidewall being extended inwardly,
said longitudinal edge surfaces of the barrier being received at said inwardly
extended portions respectively, thereby positioning said barrier at said
inward
spacing from, and facing, said interior surface of part of the sidewall.
As there is no outward extension from the body, as in Figure 3, to
form the spout, a liner of the first aspect of the invention can fit into
existing
ladles without modification, i.e. the ladles can remain of cylindrical or of
truncated cone shape and do not need to be modified to accommodate any
outward extension of the liner. However, such a liner can be customized to
fit any lip design that the foundry has or prefers. A low cost solution is
thus
provided, by the elimination of the body extension and the use of a smaller
tile.
Although the barrier would preferably be flat/straight, it could be of
curved shape.
In one embodiment the longitudinal edge surfaces of the barrier are
received in respective complementary grooves in said inwardly extended
portions respectively, whilst in another embodiment respective projections of
said inwardly extended portions are received in complementary grooves in
said longitudinal edge surfaces respectively.
Desirably said inwardly extended portions of the sidewall provide
respective flat facing surfaces, which are a preferably parallel, and at
which,
more desirably, said longitudinal edge surfaces of the barrier are
respectively
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received, with said barrier, if flat, being disposed normal to said flat
facing
surfaces.
Refractory cement or other suitable fixing means is used to fix the
barrier in place at said inwardly extended portions. Alternatively the barrier
can be secured in place as part of the manufacture of the body of the liner.
The barrier desirably terminates spaced from the lower closure floor
of said body, but in another embodiment it can extend to said floor, with
there being an aperture therein adjacent its lower end to allow molten metal
to pass, in use, into said spout. Conveniently the barrier extends from the
level of the open top of said body.
Advantageously the barrier is in the form of a refractory tile. In one
embodiment the tile is of castable material.
Conveniently the liner is of KALTEK material, and desirably
the barrier is of refractory/ceramic material, i.e. highly refractory and not
organically bonded material.
According to a second aspect of the invention there is provided a ladle
comprising an outer metal shell defining a hollow interior, the shell having a
continuous inner sidewall, bounding said interior of the shell, a lower
closure
floor and an open top, and the ladle also comprising a liner, retained in said
interior of the shell, in use, the liner comprising a body of refractory
material
defining a hollow interior, the body having a continuous sidewall bounding
said hollow interior, a lower closure floor and an open top, a barrier of
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refractory material facing an interior surface of part of the sidewall of the
body and being spaced inwardly therefrom in said hollow interior of the
liner, the barrier extending from at or near the open top of the body towards
said lower closure floor of the liner to define, with said facing part of said
inner sidewall of the liner, a spout for supplying molten metal, in use, from
said interior of the liner, the barrier having two longitudinal edge surfaces,
two facing portions of the inner sidewall of the liner being extended
inwardly, said longitudinal edge surfaces of the barrier being received at
said
inwardly extended portions respectively, thereby positioning said barrier at
said inward spacing from and facing, said interior surface of part of the
sidewall.
As there is no outward extension from the body of the liner below the
pouring lip thereof, the ladle shell similarly does not need to be extended
outwardly to accommodate such a liner extension. Thus existing ladle shells
can be lined with a liner of the invention without the need for modification.
The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
Figure 1 is a plan view of a prior art liner for a ladle,
Figure 2 is a similar view to that of Figure 1 of another prior art liner
for a ladle,
Figure 3 is a similar view to that of Figure 1 of a still another prior art
liner for a ladle,
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Figure 4 is a similar view to that of Figure 1 of a ladle liner of the
invention,
Figure 5 is a top perspective view of a ladle of the invention,
Figure 6 is an enlarged top plan view of the ladle of Figure 5,
Figure 7 is a sectional side view of the ladle of Figure 5, and
Figure 8 is a scrap top plan view of part of another embodiment of a
ladle of the invention.
A ladle of one embodiment of a second aspect of the invention is
shown in Figures 5 to 7, with a liner thereof being shown separately in
Figure 4. The ladle is in the form of a teapot ladle having a conventional
metallic ladle shell 20 of cylindrical shape. The shell 20 is slightly
tapered,
as shown best in Figure 7, with a constant wall thickness, but alternatively
it
could be wholly cylindrical, i.e. non-tapered, and as a further alternative it
could be of non-circular section in plan, i.e. n-sided, where n > 3,
particularly square. The shell thus has a hollow interior bounded by a
continuous sidewall 21 having an inner surface 22. It is closed at one end,
its
lower end in use, by a flat lower floor 23 but is open at its other, top end.
Fitted within the interior of the ladle shell with a clearance therearound is
a
one-piece liner 24. The liner comprises a body 25 of refractory material,
preferably KALTEK material, the body being of circular section in
plan but being of slightly truncated cone form, i.e. tapering slightly
inwardly
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from top to bottom as shown in Figure 7, and thus being shaped externally to
match or substantially to match the interior shape of the ladle shell
sidewall.
The body has a hollow interior which is bounded by a continuous sidewall
having an inner surface 25a. The liner has its top open, but its bottom or
lower end is closed by a flat base or floor 26.
Within the interior of the body 25 at respective opposite sides of a
generally vertical internal surface 27 of part.of the liner sidewall, are
formed
respective inwardly extended portions 28, 29. As shown best in Figure 6,
the inwardly thickened portions which extend inwardly from the arcuate inner
surface 25a of the body 25, form respective right-angled corners having first
surfaces 28a, 29a respectively at 90 to the diameter A of the body extending
through the centre of the surface 27, and respective second surfaces 28b, 29b
at right angles to the first surfaces, i.e. parallel to the diameter A and
effectively extending from the first surfaces to the surface 27. Preferably
the
inwardly extended portions are from the open top of the body 25 to the floor
26 thereof. The size of the inwardly extending portions 28, 29 can be varied
as required, i.e. the spacing between the surfaces 28b, 29b can be larger or
smaller than that shown in Figures 4 to 7, and similarly the spacing of the
surfaces 28a, 29a from the surface 27 could also be greater or smaller than
that shown. The purpose of the inwardly extended portions is to provide
means for mounting a barrier of refractory material which faces the surface
27, but is spaced inwardly therefrom in the interior of the liner, so as to
define, with surface 27 and surfaces 28b, 29b, a spout 30 for discharging
molten metal, in use, from the interior of the ladle when it is tipped.
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The surfaces 28b, 29b could be other than parallel to diameter A, e.g.
each such surface could be at an angle thereto, and moreover each such
surface need not be flat.
In the embodiment shown, the barrier is in the form of a flat
rectangular tile 31 cast from refractory or ceramic material. Preferably the
tile would not be of KALTEK material from which the remainder of
the liner is made, but would be of refractory/ceramic material, i.e. highly
refractory and not organically bonded. As shown in the drawings, the
surfaces 28b, 29b are provided with respective facing vertical grooves of any
convenient shape, with the tile 31 having a width such that its opposite
longitudinal edges/edge surfaces can be received in said grooves to dispose
the tile vertically in the liner, as shown best in Figure 7, the tile being
spaced
inwardly and rearwardly of the surface 27, to form the spout 30 referred to
above, this again being best shown in Figure 7. The tile can be firmly
secured in position in the grooves of the portions 28, 29 respectively by
refractory cement or any other suitable fixing composition.
Alternatively the body of the liner could be formed around the tile
during manufacture. The KALTEK liner can be produced by vacuum
forming an aqueous slurry of refractory and binder around a former/mandrel,
stripping this `green' and then oven drying to cure/harden. The tile can
therefore be put in place first and the liner body formed around it to secure
it
in place. The final product is then stripped and oven dried.
With the liner positioned correctly in the interior of the ladle shell,
sand and packing, indicated at 32, would fill the clearance between the
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exterior surface of the liner and the interior surface of the ladle shell,
including the floor thereof. The ladle of Figures 5 to 7 demonstrates that as
there is no outward extension from the liner body such as that below the
pouring lip of the Figure 3 liner, the ladle shell does not need to be
correspondingly extended outwardly, as with the prior art, to accommodate
such an extension. This is clearly a desirable advantage/improvement and
satisfies a long standing problem with such lined ladles.
Accordingly, in the embodiment described, by keeping the liner as
cylindrical as possible, it can fit into existing ladles without them needing
to
be modified. In other words the outer metallic ladle shell can remain of
cylindrical or truncated cone shape and does not need to be modified to
accommodate the outward extension of the prior art liner arrangement
described in relation to Figure 3.
Accordingly once the ladle shell dimensions are known, an
appropriately sized ladle liner can be taken to a foundry, fitted and then
tested. This allows a liner supplier to take to the foundry merely the new
liner together with packing sand and other ancillary assembly supplies. The
lined ladle can then be prepared and a trial undertaken on the same day, with
the advantages of the KALTEK ladle liners demonstrated.
The cost savings of using a narrower tile more than compensates for
the need to extend inwardly the internal surfaces of the KALTEK
lining, given that the cost of conventional refractory material verses
KALTEK material is approximately 5:1. Previously it was
questioned whether providing enlarged areas by virtue of increasing the
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thickness of the sidewall, would cause a curing problem with the vacuum
formed KALTEK lining. However during experimentation and trials
it was found that the possibly expected curing problem did not materialise if
the thickness increase was not too large. Moreover, unexpectedly, it has
been found that there is not that much of an increase in KALTEK
material required as the forming operation for the liner caused the sections
in
question to `suck in' somewhat.
In selecting the width of the tile, and the amount of inward
`thickening' of the interior wall portions mounting the tile two factors
however need to be considered. Firstly the tile must not be so close to
surface 27 as to cause a`pinching' effect (reducing metal flow) at the bottom
of the tile, and secondly if the inward thickening is too great, the portions
will have too thick a section which can cause difficulties in curing during
manufacture.
Finally it is considered that the invention may result in lower
turbulence of metal flow out of the liner as a consequence of the nature and
position of the barrier.
Whilst the material of the body 25 is preferably of KALTEK
any other suitable refractory liner material could be used. Although shown
extending to the level of the open top of the body 25, the tile 31 in another
embodiment, could terminate short thereof. The tile could clearly be formed
other than by casting.
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With the embodiment of Figures 5 to 7, the tile 31 can terminate above
the inner surface of the floor 26, for example as shown in full lines and
sectioning in Figure 7, in order to allow molten metal to flow, in use, from
the hollow interior of the lining into the spout 30 for discharge from the
ladle. This arrangement is the most preferable in that the length of the tile,
and thus its cost, is minimised. However in an alternative arrangement
shown in dashed lines in Figure 7, the tile used partly to define the spout
has
a length such that it extends from the open top of the body to the floor
thereof. However to allow metal to flow from the interior of the liner to the
spout, the lower part of the tile is provided with one or more through
openings 33 of any suitable form.
Figure 8 is a scrap view of the ladle of Figures 5 to 7, modified solely
in the manner by which the tile 31a of the liner is fitted in place. Here
instead of the opposite longitudinal tile edges (edge surfaces) being received
in respective grooves in the inwardly extending portions of the sidewall,
respectively, these portions are provided with respective inwardly extending
projections 34a, 35a which fit into respective longitudinal grooves extending
within the opposite longitudinal edge surfaces of the tile, refractory cement
or
equivalent again being provided to secure the tile to the inwardly extended
portions at which the opposite longitudinal edge surfaces/edges of the tile
are
received, or the tile being secured during the liner manufacture. With this
arrangement the width of the tile could be further reduced, with the
respective projections effectively forming part of the rear wall, which, with
the facing sidewall surface, defines the spout of the lining.
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Whilst the ladle shell of Figures 5 to 7 is without a pouring lip, this
could be provided, and such a metal lip of the ladle shell packed with bonded
sand when sand is packed between a non-lipped liner and the ladle shell. In a
still further arrangement the liner and the ladle could have respective
pouring
lips, so that the ladle shell is in the form of a lip pour ladle, and the
teapot
liner is intended specifically therefor.
As shown with the embodiment of Figures 5 to 7, the inwardly
extending portions are at respective portions of the sidewall of the liner
which are relieved inwardly from the exterior thereof, to reduce the
KALTEK material required.
Accordingly it will be appreciated that the problems and disadvantages
of the prior art referred to are overcome by this invention. If required, the
only item specific to the foundry would be the lip design. Any lip design
which a foundry prefers can easily be customized for production. An initial
trial can be run with a prototype liner by building the lip out of
conventional
refractory material. If the product proves to be of economic benefit, the
specific lip design can then be built into the one-piece liner design and sold
as
a custom unit.
