Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to metal castiny
and more in particular to a process and apparatus for
continuous casting of metalO
The invention is well adapted to casting oE
various ferrous and nonferrous metals, such as light
aluminium- and magnesium-base metals and alloys, when
a continuously-cast section is withdrawn from the
mould horizontally or at an angle to the horizontal.
There are known various techniques for hori-
zontal continuous casting of metal (see a book by
E. German, entitled "Continuous Casting", Metallurgizdat
Publishers, Moscow, 1961,p. 168, FIG. 488; p. 170,
FIG. 495; p. 200, FIG. 582), which consist in that a
casting formed in a mould and a secondary-cooling zone
is then withdrawn in a stepwise manner from the mould
so as to be further severed to measured lengths.
A horizontal continuous-casting machine
generally comprises a tundish, a cooled mould, a
system for feeding molten metal into the mould, a
secondary-cooling chamber, and a casting withdrawal
mechanism.
The prior art continuous casting processes
are disadvantageous in that they fail to ensure the
production of high-quality castings.
There is also known a process and apparatus
for horizontal casting of metal ~see a book by V.
Shwarzmeier, entitled "Continuous Casting",
Gosnauchtekhizdat Publishers, Moscow, 1962, p. 226)
wherein a rnolten metal is fed into a horizontal mould
by means of a closed sectional pipeline. The molten
metal fed into the pipeline is raised to a level
slightly above the mould, whereupon the metal is gravity
fed into the mould to solidify therein, i.e. the
casting process can be discontinued at will.
6~76
3 -
However, the above process also fails to
ensure good quality of castings.
There is further known a process and apparatus
for horizontal continuous casting of metal (see a book
by O.A. Shatagin, V.G. Sladkoshteev et al., entitled
"Horizontal Continuous Casting of Nonferrous Metals
and Alloys", Metallurgizdat Puhlishers, Moscow, 197~,
pp. 42-44, FICS. 14-16). According to this process,
a molten metal is fed into a mould from a holding
furnace through a tightly closed tundish. The metal
is delivered into the mould under pressure, which
depends upon the height as measured from the metal
meniscus to an opening in the horizontal mould. The
casting formed in the mould is then withdrawn there-
from in a step-wise manner, passed through the
secondary-cooling zone and finally cut to measured
lengths.
The above-described process makes it
impossible to control the initial stage of the casting
forrnation or to improve the casting structure in cross
section. The apparatus for performing this process is
likewise unsuitable for improving the structure of the
casting being produced.
There is also known a continuous casting
process and apparatus as disclosed in USSR Inventor's
Certificate No. 265385, which allow an overpressure to
be built up in the liquid phase of the casting at
intervals between the withdrawal cycles and a drop in
pressure prior to the casting withdrawal operation,
whereupon the casting is cooled in the secondary-
cooling zone and then is cut to measured lengths. The
apparatus for performing this process comprises a metal
supply system including a tundish, an adapter with
intercommunicating channels, a mould, a secondary-
i7~
cooling chamber, a mechanism for intermittent withdrawalof the casting from the mould, and an arrangement for
severing the casting into measured lengths.
The above described process and apparatus
fail to ensure good quality of the cast product and
make it impossible to set up favourable conditions for
the formation of castings in the mould, for example,
by producing pulsating pressure at the side of molten
metal on the solidifying skin of casting. Also, no
provision is madefor introducing a powdered material
into the molten me-tal.
It is an object of the present invention to
provide a continuous casting process and apparatus
which will permit improved quality of the cast product
to be obtained by producing a pulsating pressure in
the molten metal of the casting being formed during
reciprocating motion of the molten metal between a
metal feeding duct and an auxiliary vessel.
Another object of the invention is to step
up the metal casting speed by introducing a powdered
material into the molten metal fed for casting.
These and other objects of the invention are
accomplished by providing a continuous casting process
which comprises feeding a molten metal into a mould
from a metal supply system through a metal feeding
duct, effecting a step-wise withdrawal of a solidifying
casting for a given length from the mould while supply-
ing a next portion of molten metal thereinto, producing
a superpressure on the solidifying skin of casting at
the side of molten metal at intervals between the
casting withdrawal cycles, wherein, on completion of
the casting withdrawal cycle, the molten metal is fed
from the metal supply system into an auxiliary vessel
prefilled with an inert gas and a preset pressure is
-- 5
built up in the molten metal inside the auxiliary mould
and in the solidifying casting, whereupon the molten
metal is caused to move to and fro between the auxiliary
vessel and the metal feeding duct incorporated in the
metal supply system, with the molten metal being fed
into the mould from the auxiliary vessel and the metal
supply system during the next casting withdrawal
cycle.
Prior to feeding the molten metal into the
mould from the auxiliary vessel, a powdered material is
preferably introduced into the metal in an amount rang-
ing from 0.001 to 50 per cent of the amount of the
molten metal fed from the auxiliary vessel, and while
the casting is withdrawn from the mould, a suspension
of the powdered material and the molten metal is con-
currently fed into the mould.
The invention also provides apparatus for
performing the continuous casting process, which com-
prises a metal supply system with a metal Eeeding duct,
an adapter with intercommunicating channels of which
one is connected to the metal feeding duct and another
one to a cooled mould, a secondary-cooling chamber
with a casting withdrawal mechanism, wherein the
adapter is positioned above the metal feeding duct
and has an additional channel in communication with
other channels provided therein and, mounted on the
adapter at the side of the additional channel, is an
auxiliary vessel having a gas supply system connected
thereto at its upper part.
The auxiliary vessel is suitably provided
with a system for supplying a powdered material.
Preferably, the auxiliary vessel is equipped
with an electric heater.
In addition, the auxiliary vessel is prefer-
ably furnished with a device for induction stirring
of the mo]ten metal and powdered material, said device
being mounted externally of the auxiliary vessel on
the side surface thereof.
With the continuous casting process and
apparatus of the invention it becomes possible to
improve the quality of the cast product, to step up
the metal casting time and to enhance operating
reliability of the apparatus.
The invention will be further described, by
way of example only, with reference to the accompanying
drawing in which a single Figure shows a general view
of an apparatus for horizontal continuous casting of
metal.
The process according to the invention for
continuous casting of metal is carried out as follows.
Continuous casting of metal is effected by
causing the molten metal to reciprocate continuously
or intermittently between a metal feeding duct and an
auxiliary vessel which is prefilled with an inert gas
and into which the molten metal is fed after the casting
is withdrawn from a mould In the course of the
withdrawal operation the mould is replenished with the
molten metal from the auxiliary vessel.
To improve the structure of the casting being
formed, by way of increasing the number of solidifica-
tion centres and the rate of the casting throughout
solidification, prior to feeding the molten metal into
the mould from the auxiliary vessel, a powdered material
from aluminium alloy or iron is introduced into the
metal inside the auxiliary vessel in an amount of up
to lO per cent of the amount of mol-ten metal contained
in the auxiliary vessel and then a suspension of the
7~
powdered material and molten metal is introduced into
the mould during the withclrawal cycle.
The invention will now be described by the
following illustrative Examples~
If castings are produced, for example, from
aluminium alloy.
xample 1
With the casting diameter of 100 mm, the
length of withdrawal - 500 mm, the withdrawal time -
3 sec, the interval - 27 sec, and the pulsating
pressure in the molten metal -- 2 ato, the number of
pulsations was 10, and the casting rate - 1 m/min.
Example 2
With the casting diameter of 200 mm, the
length of withdrawal - 1000 mm, the withdrawal time -
5 sec, the interval - 25 sec, and the pulsating
pressure in the molten metal - up to 2.5 ato, the
number of pulsations was 10 to 15, and the casting
rate - 2.0 m/min.
If castings are made from the same aluminium
alloy, but with addition of a powdered material.
The percentage of the solid preground material
to be added into any metal being cast depends on the
following factors:
1/ the absence of overheating of the metal
being cast;
2/ the occurrence of overheating of the
metal being cast;
3/ the addition of a powdered material or
granules.
In the absence of overheatins, a powdered
material is added in an amount ranging from OoO01 to
10 percent of the amount of metal, and granules are
added in an amount ranging from 10 to 25 per cent of
the amount of metal.
7~
,.
In additi~n, the auxiliary vessel is prefer-
ably furnished wi~h a device for induction stirring
of the molten metal and powdered material, said device
being mounted externally of the auxiliary vessel on
the side surface thereof.
With the continuous casting process and
apparatus of the invention it becomes possible to
improve the quality of the cast product, to step up
the metal casting time and to enhance operating
reliability of the apparatus.
~ The invention will be further described, by
way of example only, with reference to the acCQmpanying
drawing in which a single Figure shows a general view
of an apparatus for horizontal continuous casting of
metal.
The process according to the invention for
continuous casting of metal is carried out as follows.
Continuous casting of metal is effected by
causing the molten metal to reciprocate continuously
or intermittently between a metal feeding duct and an
auxiliary vessel which is prefilled with an inert gas
and into which the molten metal is fed after the casting
is withdrawn from a mould. In the course of the
withdrawal operation the mould is replenished with the
molten metal from the auxiliary vessel.
To improve the structure of the casting being-
formed, by way of increasing the number of solidifica-
tion centres and the rate of the casting throughout
solidification, prior to feeding the molten metal into
the mould from the auxiliary vessel, a powdered material
from aluminium alloy or iron is introduced into the
metal inside the auxiliary vessel in an amount of up
to 10 per cent of the amount of molten metal contained
in the auxiliary vessel and then a suspension of the
f
~ .
1 accommodates a metal feeding duct 8 having its one
end immersed in the molten metal 2 and the other end
pressed against the cover 3 by the refractory adapter
5 through a flange 9 and refractory cement. The cover
3 has a tightly closed opening (not shown) through
which the molten metal is fed into the tundish 1 and
an opening 10 adapted to admit a compressed gas into
the tundish 1.
There is provided a cooled mould 14 which is
connected to the horizontal channel 7 through a refrac-
tory sleeve 11 and a packing 12 by means of a clamping
ring 13. Positioned after the mould 14 is a mechanism
15 for the stepwise withdrawal of a casting 16 from
the mould 140
The refractory adapter 5 is formed with an
additional channel 17 which is arranged therein co-
axially with the vertical channel 6 and which communi-
cates with the horizontal channel 7 and with an auxi-
liary vessel 18 mounted on the metal casing 4 of the
refractory adapter 5 in alignment with the vertical
channels 17 and 6. The interior surface of the
auxiliary vessel 18 is lined with a refractory 19.
Connected at the top to the auxiliary vessel
18 through a change-over valve is a gas supply system
21 and a container 22 for a powdered material, incor-
porated in a system for feeding a precrushed soli.d
material.
The auxiliary vessel is provided with an
induction stirrer 23 for stirring the molten metal and
powdered material. If necessary, the auxiliary vessel
18 is equipped with an electric heater 24. To initiate
the casting process a dummy bar is required.
The continuous casting process as performed
by the apparatus of the invention is carried out as
follows.
~t~ ~7
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1. Feeding the molten metal 2 into the tundish
1 through the tightly closed opening in the cover 3
until it reaches a preset level in the tundish 1,
whereupon the latter is sealed.
2~ Heating, if necessary, the auxiliary vessel
18 by means of the electric heater 2a several seconds
prior to feeding the molten metal 2.
3. Introducing a dummy bar into the mould 14
by means of the casting withdrawal mechanism 15 and
]0 pressing it against the refractory sleeve 11.
4. Feeding a gas, preferably inert, from the
gas supply system 21 into the tundish 1 through the
opening 10 in the cover 3 and then building up an
initial superpressure P sufficient to permit the molten
metal 2 to pass along the metal feeding duct 8,
vertical duct 6 and additional channel 17 and fill the
horizontal channel 7 until the molten metal 2 comes in
contact with the dummy bar and then fills the auxiliary
vessel lB until it reaches a preset level, for instance,
at half the height of the auxiliary vessel 18.
The casting withdrawal mechanism is then
operated to move the dummy bar for a given distancel
preferably equal to a measured length of the severed
casting 16. The distance of withdrawal should not
exceed the length of the mould 14.
As the dummy bar is pulled out from the mould
14, the latter is filled with metal, which may be fed
either from -the tundish 1 or from the auxiliary vessel 18.
For the skin of casting to be formed at a new
section of the casting 16~ an interval between with-
drawing cycles is necessary. The duration of this
intervalis calculated in accordance with the cross-
sectional dimension of the casting 16, the distance of
withdrawal and the length of the secondary~cooling
c, i,
....
ot~
zone (it has been calculated to be in the range of 10
to 60 sec).
At the initial stage of this interval, the
pressure of gas in t~e tundish 1 is raised to a preset
value Pl, it being up to 2 - 3 ato for aluminium alloys
and up to 3 - 5 ato for steel. This creates favourable
conditions for the initial formation of the skin of the
casting 16, with the skin being in intimate contact with
the cooled walls of the mould 14. As a result, it
becomes possible to produce castings with a high-
quality surface.
With the increase of gas pressure in the
tundish ]. to a preset value Pl, the gas pressure above
the metal meniscus in the auxiliary vessel 18 is raised
to a value
2 Pl h ~, where
h is the distance between the metal meniscus
in the tundish land in the additional vessel 18, cm;
~ is the specific weight of the molten metal 2,
g/cm .
During the next period of the interval, the
gas pressure is repeatedly varied either in the tundish
1, for instance, by a value of + 1 ato of the preset
value (equalling 2 to 3 ato), or in the additional
vessel 18 by a value
+ P3 hl~ t where
hl is the preset distance between the upper and
lower levels duriny rise and fall of the molten metal
2 in the additional vessel 18, cm;
~ is the specific weight of the molten metal,
g/cm .
Although the change of the gas pressure in
the additional vessel 18 by the indicate value of
+ 1 ato is followed by relatively insignificant rises
d 6
- 12 -
and falls of the molten metal 2 in the additional
vessel 18 and by relatively insignificant movements
of the molten metal 2 in the vertical channels 6 and
17l pulsations in the pressure acting on the solidify-
ing skin of casting are substantial and a certain move-
ment of the molten metal 2 occurs in the casting 16
due to bulging and shrinking of the skin under the
action of pulsating pressure. The above factors are
conductive to the formation of castings in cross
section and, especially, to the formation of the core
portion thereof.
A constant change of the gas pressure in the
additional vessel 18 by a value of + P3 leads to a
continuous appreciable movement of the molten metal 2
in the vertical channels 6 and 17, which eliminates
the danger of the metal freezing in the channels at
intervals between the withdrawal cycles, ensures good
stirring of the molten metal 2 in the tundish 1 with
the resultant improvement in its chemical composition
and structural uniformity, and produces, though in a
smaller amount as compared -to the previous example,
useful pulsating pressure acting on the skin of casting
at the side of the molten metal 2.
Towards the end of the interval between the
withdrawal cycles the level of the rnolten metal 2 in
the auxiliary vessel 18 is raised to a maximum height
while discharging gas from the auxiliary vessel 18
and closing the gas feeding valves 20 therein.
If the molten metal 2 is to be fed into the
mould 14 from the tundish 1, the initial gas pressure
P is set in the latter. When the mould 14 is fed
with the molten metal 2 from the auxiliary vessel 18,
the gas pressure in the tundish 1 will be equal to
the atmospheric.
jt7
- 13 -
Then, by means of the dummy bar and later
with the aid of the withdrawal mechanism 15, the
casting l6 being formed is pulled out from the mould
14 for a given length.
In order to effect appropriate treatment of
the molten metal 2 to be cast, it is fed from the
tundish 1 not into the mould 14 but into the auxiliary
vessel 18 prior to commencing the casting withdrawal
operation. As the casting 16 is withdrawn from the
mould 14, the latter is concurrently replenished with
the pretreated molten metal 2.
The metal treating procedure may include the
steps of controlling the metal temperature conditions
and adding a powdered material into the molten metal
before the casting 16 is withdrawn from the mould 14.
Once the molten metal 2 in the additional vessel 18
is raised to a maxi.mum level, the valve 20 is closed
to discontinue the supply of gas to the additional
vessel 18 and is opened to admit into the latter a
preset portion Gf powdered material fed from the
container 22.
To effect good intermixing of the powdered
material with the molten metal 2, the induction stirrer
23 is operated immediately after or simultaneously with
the introduction of the powdered material to cause
rotation of the resultant mixture.
The process and apparatus of the invention
make it possible to reduce, for example, power capacity
of the induction pump used in the supply system by
feeding the molten metal into the mould from the addi-
tional vessel and from the supply system. Since a
greater amount of molten metal is sometimes delivered
from the additional vessel, the process and apparatus
permit the use of a solid preground material.
.:,;
, ~
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The introduction of a powdered material into
the molten metal makes it possible to reduce the metal
solidification time in the casting with the resultant
improvement of its structure When the solid pre-
crushed material is introduced into the molten metal
in the form of granules, these are often heated to a
temperature close to the melting temperature and thus
are partially melted down. As a result, the metal
solidiication time in the casting is reduced and its
structure is improved.
By replenishing the mould with the molten
metal from the auxiliary vessel, into which the molten
metal is fed prior to the casting withdrawal opera-tion,
it becomes possible to carry out an appropriate treat-
ment of the molten metal before delivering the latter
into the mould.
Continuous stirring of the molten metal in
the region between the metal feeding duct and the
auxiliary vessel renders it possible to make the metal
being cast homogeneous in chemical composition.
In additionf the process of the invention
prevents the freezing of metal in the metal feeding
channels during a prolonged interval between the with-
drawal cycles and also permits a useful pulsating
pressure to be applied onto the solidifying skin of
casting at the side of molten metal. This being a
positive factor conducive to the increase in the
amount of sappy structure in the casting cross
section, resulting in an improved quality of the
cast product.
With the use of an electric heater in the
additional vessel it becomes possible to prevent the
freezing of metal on the inner walls of the additional
vessel, especially at a time when solid preground
- 15 -
materials are added into the molten metal during
casting of certain types of refractory metals.
The provision of a device for induction
stirring of the molten metal and powdered material
permits effective intermixing thereof to be carried
out with a view to improving quality of the cast
product.
