Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relate to machines and
processes for the casting of discrete solid shape~ from
a flowable; moldable or molten materialO Specific:ally,
the inventlon disclose~ continuously ca~ting disc~ete
shapes using a static mold ca~ting ~achine or,
preferably, a moving mold casting machina whera, ~or
example, the shapes aro form~d between spaced port:ions
o~ a palr o~ endless ~lexible casting belt~ wh~ch ara
moved along with opposit~ sur~aces o~ th~ matal be~ng
cast~
Although the principles of the invention can
be used to cast any ~lowabls, moldabl~ or molten
material such as plastlcs~ the invention will be
described in terms of continuously casting molten metal
}5 into discrete and variabla shapes, such as ingot~,
anodes, wirebars or ~oundry castings.
Discrete metallic shapes are typically cast in
individual molds using a discontinuou~ stream of molten
metal. A plurality of mold cavities are supplied
sequentially and the flow of metal in the desired
quantity to each of the molds is controlled manually by
an operator or in an automated manner. Continuous
casting is employed, in a variety of forms, in the
nonferrous and ferrous metals industry and elsewhere, to
decrease production cost and increase product quality.
Two basic systems known as the static and moving mold
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methods are used in continuous casting o~E shapes such as
billets or continuous strips. In the static mold
casting machine, the walls of the mold are stationary,
while the cast products move against and solidi~y within
tham. Moving mold casting machines emplvy a belt,
chain, drum, wheel, or other surface which moves at
approximately the same speed as the solidifying metal.
The continuous casting of metal on moving mold
casting machines having at least one movable belt and a
corresponding fixed or movable surface which together
form a mold of two opposed surfaces in which the cast
material solidifies is described in detail in the
~ollowing U~S. patents which are incorporated herein by
re~erence: 2,631,343; 2,904,860; 3,036,348; 3,123,873;
3,123,8~4; 3,167,830; 3,533,4~3, 3,864,973; 3,878,883;
3,921,697; 3,9~7,270; 3,937,~74: 3,94~,8~5; 3,955,~15;
~,002,197; and 4,854,371.
For a twin belt caster where two movabl~ belts
form the mold, in operation, a continuou~ strea3n of
molten metal is supplied at the inlet of the machine to
a cavity ~ormed by a pair of movable flexible casting
belts, positioned generally above the other, and side
dam blocks, and emerges at the other end of the cavity
(outlet of the machine) as a solidified strip or bar of
metal. The strip or bar is subsequently fed to other
apparatus for mechanical working, or cutting and~or
welding, which changes its cross sectional dimensions.
For example, twin belt casters o~ the type desc:ribed are
used to convert molten copper to a roughly rectangular
bar shape which is then continuously fed to a rolling
mill ha~Ting a series of rolling stages for converting
the rectangular bar to a round rod. Typically, the rod
eventually is drawn to wire of various gauges.
In a previous attempt in the art to produce
shaped articles continuously, a twin belt caster was
modified by making the dam blocks smaller at certain
inter-rals to provide a cast material having the shap~ of
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an anode, i.e., a flat rectangular shape having support
arms. After casting, however, the casting had to be cut
~o form discrete anode shapes.
Another continuous casting moving mold method
employs ~ casting wheel ha~ing a peripheral groove
therearound. A portion of the peripheral groove is
closed by an endless belt to form a mold into which
molten metal is poured to be solidified into cast metal
and discharged therefrom. Such designs may be seen in
U.S. Patent Nos 3,279,000 and 3,46~,620, which patents
are hereby incorporated by reference.
Continuous casting using a static mold may be
found in U.S. Patent Nos. 2,938,251; 2,946,100;
3,066,364; 3,0~9,209; 3,098,269; and 3,115,686, which
patents are here~y incorporated by reference.
Basically, molten metal i~ continuously ~ed into the
mold, freezes and the frozen product continuously
removed from the mold. Generally, the mold is in a
vertica} position with the molten metal poured into the
top of the mold.
While the casting machines described
hereinabove are very successful and employed extensively
throuqhout industry, the need still exists for these
typa continuous casting machines to produce discrete
shapes. It is an object of the invention to provide
apparatus and methods for the cont;nuous casting of such
discreta shapes.
SUMMARY OF THE INVENTION
The present invention is directed to an
improvement in continuous casting machines and comprises
apparatus and method for using a continuous casting
machine to cast discrete shapes such as wire bars,
ingots, billets, cakes, strips and foundry shapes from a
stream of molten material. A~though the invention can
be employed in connection with various types of
continuous casting machines, the invention for
convenience wi~l be described in detail for casting lead
2~
pigs using a twin belt caster wherein a pair o~ moving
belts form a moving mold for molten metal.
The apparatus and method of the inv~ntion can
be employed with any flowable, moldable or molten
material such as plastlcs, ferrous or non~errou5 metals
including but not limited to steel, iron, copper, lead,
bismuth and aluminum. The invention is particularly
useful for the continuous casting of brittle or
frangible materials which cannot normally be rolled,
roll-formPd, drawn or drilled in the solid state.
The method o~ the inventio~ comprises the
steps of supplying a continuous stream of molten
material to a mold, static or movinq~ forming the
continuous stream of molten material into discrete)
segments of predetermined volume and shape ~ olidifying
said molten material and separating said segments into
discrete shapes, said forming step taking pl~ce prior to
any significant solidification of the molten metal. Tha
~orming step may be accomplished by using for~ng means
such as inserts, dividers, spacers, and the like as will
be described further hereinbelow.
The apparatus of the invention comprises a
continuou~ casting machine having first means for
def~ning a mold, said first means including a moving or
static surface depending on the mold employed, second
means for supplying a continuous stream of molten
material to the mold, one or more forming members which
form discrete chambers in the mold and form the molten
material in the mold into a cast material in the form of
discrete segments, solidifying means and separating
means to separate the discrete segments into discrete
shapes from the cast material. For a twin-belt caster
the moving surface is planar whereas for a wheel ~aster
the movin~ surface is curved. In a static mold, the
mold is substantially stationa~y relative to the molten
material and solidified material moving through the
mold. Static molds frequently employ reriprocating or
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other vibrating motions while casting.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic illustration of a twin-
belt casting machine showing the improved forming means
for forming discre~e shapes.
Fig. 2 is a side sectional view taken along a
plane perpendicular to the input rolls and including the
tundish, dam wall and molten metal.
Fig. 3 is a top view of the lower casting belt
showing an ingot shape formed using a particular forming
means.
Fig. 4 is a side view of the lower casting
belt showing an ingot shape ~ormed using a particular
forming means.
~ETAILEp DESCRIPTION OF 5'HE I~V~NTION
An illus~rative example cf a contlnuous ~etal
castinq machine equipped with an emb~dimen~ of the
present invention ls shown in Fig. 1. In this casting
machine 10 molten metal 11 is supplied from a pouring
box or ladle (not shown~ into a tundish 12. From the
tundish 12, the molten ~etal 11 is ~ed into an input
rsgion 13 formed between spaced parallel surfaces of
upper and lower endless flexible castin~ belts 14 and
lS, respectively. The cavity formed between the belts
14 and 15 and dam blocks 16 may be defined as the
casting region 17 wherein the molten metal is cast into
a desired shape and solidified. The casting belts are
preferably fabricated from steel, or other alloys, which
provide toughness and resistance to abrasion and
physical damage as well as resistance to the temperature
shocks and heat differential stresses undergone during
casting.
The casting belts 14 and 15 are supported on
and driven by an upper and lower carriage generally
indicated at 18 and 19, respectively. Both carriages
are mounted on a machine ~rame (not shown). Each
carriage includes two main rolls which support, drive
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and steer the casting belts. These rolls include upper
and lower input rolls, 20 and 21, and upper and lower
output rolls, 22 and 23, respectively.
A 1exible, endless side metal retaining dam
16 is disposed on each side of the casting belts to
define the side edges o~ the casting region for
confining the molten metal. The sicle dams 16 are quided
at the input end of the casting apparatus 10 by crescent
shaped member~ ~4 which are mounted on the lower
carriage 19.
During the casting operation, the two casting
belts 14 and 15 are driven at about the same linear
speed by a driving mechanism and the upper and lower
carriages are preferably downwardly inclined in the
downstream direction, so that the casting r~gion 17
between the casting belts is inclined. ~his do~lward
inclination facilitates flow of moltan me~l into tha
casting region.
~fter the castings have solidified and leave
the appaxatus as indicated at 25, secondary coo}er means
26 may be employed to completely solidi~y and/or cool
the casting. The use of this technique i5 called
"secondary cooling" and is used to generate hi~her
casting speeds. The use of ~econdary cooling also
~acilitates removal of the forming means 27 from the
cast metal by a thermal shock mechanism caused by
different coefficients of expansion between the forming
means and the cast metal. Greater differences between
the coefficients will have a greater thermal shock and
separation effect. The primary cooling means (not
shown) is generally accomplished by the use of a high
velocity moving liquid coolant travelling along the
opposite sides of the belts 14 and 15 which form the
mold.
The improved apparatus and method of the
invention utilizes for u~gL~ z~ ehe castinq belts
to provide a discrete shape in the mold and casting
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region 17 o the apparatus. The forming means 27 are
preferably attached to the upper casting belt 14 and may
vary in shape and spacing to define the desired mold
shape in the casting region 17 o~ the apparatus.
Exemplary forming means designs are described
hereinbelow.
In a preferred embodiment of the invention, an
additional carrîage 28 and belt 29 are utilized to allow
the forming means 27 to be separated from belt 14,
collected in timing device 30 and positioned on belt 14
based on a predetermined desired spacing. By the use of
this separator system, the weight ~and size) of the
discrete shapes cast during the casting operation may be
varied by adjusting the timing device 30. Carriage 28
may employ two rolls 31 and 32 as indicated.
The discrete shapes 33 are ~ed out oP the
casting apparatus and transported to a desired location.
The caster 10 and the tundish 12 are
preferably of the "open pool" type with the tundlsh
outlet specially modified to permit the ~orming means 27
to enter the casting area 17. The pool of molten metal
at the caster inlet 13 preferably fills the inlet 50
that the forming means 27 contacts the molten metal 11
at the inlet 13.
The tundish tip is preferably made of graphite
or other soft, ablating material which will also help
the casting and lubrication of the lower belt 15. A
drawing of the proposed arrangement is shown in Fig. 2.
Since the metal, the belt, and the forming means all
meet at approximately the same point, any gas or vapor
behind the forming means 27 can escape into the open
atmosphere and not cause a bubble to form behind the
forming means in the metal casting. The da~ blocXs 16
preferably have a very slight taper on the internal
surface ~larger at the bottom) to prevent the forming
means from turning or otherwise moving inside the mold.
As the metal passes through the caster,
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operation will be identical to a standard caster.
However, the casting rate will generally be accelerated
or inhibited ~y the use of the ~orming means 27 which
ac~ a~ heat sinks or insulator~ depending on th~
S material used for the ~orming mean~.
In a preferred emhodiment, the forming means
27 are removably attached, e.g., mag~etically, to belts
14 and 29. In operation, the forming means will be
spaced on belt 14 and, as the belt rPvolves, the desired
casting shape will be formed. After solidification, the
discrete casting will be separated from the continuous
cast strip (containing the forming means 27) with the
forming means becoming magnetically attached and
transferred to belt 29. The forming means ~7 wil:l then
be transferred to the timing davice 30 where they will
be al~gned and released again to belt 14 at the d~sired
spacinq.
A device ~or separating the discrete castinys
from the strip of castings made in tha caster ~ay be
conveniently employed at point 34. For example, a
bending movement may be applied to the casting wlth the
forming means 27 taken off on belt 29 and transferred to
the casting belt 14 as described hereinabove.
The designs for the forming means 27 can be
quite variable. As shown in Fig. 3, a U-shape forming
means 27 produces an ingot shape 33. Likewise, Fig. 4
shows an inverted T-shape forming means 27 which also
produces an ingot shape 33. If required, boles, Yoids,
indentations, brand names or other marks can be put into
the casting with suitable forming means.
The forming means 27 may be made from a
variety of materials. For magnetic dividers, the
stronger the magnetic force of the forming means, the
less internal taper or alignment will be needed to lock
the forming means in the mold space. In some
applications, it may even be desirable to make the
forming means partly or wholly out o~ foundry sand, or
~t~
g
refractory or metal beads as a substitut2 for drilling
or casting complex holes and shapes in a casting or as a
divider.
Removal of the ~or~ing mean~ 27 from the belt
14 and/or the casting may be facilit,ated by using
forming means which are consumable ~such as wood) or
disposable. Another design is to employ a thin,
flexible walled forming means containiny a substance
such as wat~r which expands when contacted with the
lo molten metal (because of the generation o~ vapor or
steam in the formin~ means) and which contracts upon
cooling. Thus, as the forming means contact the molten
metal 11 the forming means ~xpands and the casting is
formed with the expanded for~ing means. After
solidification and cooling, the ~orming means contracts
facilitating its removal. A thin gauge ~talnless steel
forming means may suitably be employed to cast lead
pigs.
In an apparatus employing a casting wheel,
fo~ming means 27 may be placed on the wheel or belt to
define the discrete shape desired in the mold being
formed by t~e peripheral groove in the casting wheel and
the endless belt as discussed hereinabov~. For
continuous casting using a static mold, the forming
means 27 may be inserted into the mold cavity at clesired
intervals to provide a separation between the molten
metal (a division into discrete shapes~. Refractory
beads may suitably be employed whereby the beads are fed
into the mold cavity forming a separation between the
molten metal being cast. The cast metal may then be
easily separated into discrete shapes after
solidification.
