METHODE ET DISPOSITIF DE COULEE EN MOULE SOUS PRESSION

METHOD AND APPARATUS FOR PRESSURE DIECASTING

Abrégé anglais

ABSTRACT OF THE DISCLOSURE:
A pressure die-casting method and apparatus in
which the melt from a molten metal reservoir is delivered
and fills the casting die under the action of a difference
in pressures created in the molten metal reservoir and
the casting die and when the melt fills the die it is
under the action of vacuum, ambient or increased gas
pressure. The method is characterized by that after
filling the casting die with melt up to a preset level in
the unfilled cavity of the casting die or in one or several
unfilled independent cavities of the die an additional
gas pressure considerably higher than that acting already
in the casting die is created and simultaneously this
additional gas pressure is equalized by the counter acting
pressure created on the other side of the casting die.

Revendications

The embodiments of the invention in which
an exclusive property or privilege is claimed are defined
as follows:
1. A pressure die-casting method in which the
melt from a molten metal reservoir is delivered and fills
the casting die under the action of a difference in pres-
sures created in the molten metal reservoir and the casting
die and when the melt fills the die it is under the action
of vacuum, ambient or increased gas pressure, characterized
by that after filling the casting die with melt up to
a preset level in the unfilled cavity of the casting die
or in one or several unfilled independent cavities of the
die an additional gas pressure considerably higher than that
acting already in the casting die is created and simul-
taneously this additional gas pressure is equalized by the
counter acting pressure created on the other side of the
casting die.
2. A method according to claim 1 characterized
by that the additional gas pressure is maintained constant
until the complete crystallization of melt in the casting
die.
3. A method according to claim 1 characterized
by that the additional gas pressure rises continuously
from the moment of its creation until the completion of
melt crystallization in the casting die.
4. Apparatus for pressure die-casting,
comprising:
- a reservoir,
- a casting die made of two-parts and comprising
a cavity, said reservoir being connected to said casting-

die, and said casting-die having an additional cavity,
- a first source of pressure to which said
reservoir is connected,
- a second source of pressure, to which said reser-
voir is connected,
- a multiplying cylinder connected to said casting
die, said multiplying cylinder being also connected to said
additional cavity and to said second source of pressure.
5. Apparatus according to claim 4, wherein:
- said reservoir which contains molten metal
is connected to said casting die by means of a material feed
conduit,
- said casting die comprises a lower part and an
uppper part forming said cavity, said additional cavity
being formed in the upper part of said casting die,
- said first source of pressure is a delivery
pressure P1, and
- said second source of pressure is a high pres-
sure P3.
6. Apparatus according to claim 4, wherein:
- said reservoir is connected to said casting die
by means of a riser duct,
- said casting die comprises a right part and a
left part forming said cavity and said additional cavity,
- said first source of pressure P1 is connected
to said reservoir by means of a valve, a conduit and a
power cylinder having a pressure indicator,
- said second source of pressure is a high pressure
P3, said power cylinder is connected to said multiplying
cylinder one part of which communicates with said cavity
and by means of a valve with said second source of high
pressure,
- said pressure indicator being connected to a

transducer which is connected by means of a valve to
said additional cavity and to said multiplying cylinder,
- a control gate being provided between said
transducer and said additional cavity.
7. Apparatus according to claim 5, wherein:
- said reservoir is connected to said first
pressure source by means of a first valve, and to said
casting die by means of a pressure indicator provided
with a transducer, said transducer communicating with
said high pressure source by means of a second valve,
- said source of high pressure being connected to
said multiplying cylinder by means of said second valve,
said multiplying cylinder communicating with the lower
part of said casting die,
- said multiplying cylinder having a space in
front of a piston inside said cylinder, said space com-
municating with said additional cavity by means of a
control gate,
- said casting die being connected with a vacuum
tank by means of a tube and a valve.
8. Apparatus according to claim 4, wherein:
- said reservoir which contains molten metal is
connected to said casting die by means of a material feed
conduit,
- said casting die comprises a left part and a
right part, said cavity being formed in-between, and said
additional cavity being formed in said left part,
- said reservoir being connected to said first
pressure source by means of a valve, said first pressure
source communicating with said casting die by means of
a valve,
- a pressure indicator provided with a trans-
ducer being fitted to said reservoir, said transducer
11

being connected by means of a valve to said high pressure
source
- said high pressure source is connected with
said multiplying cylinder and said a multiplying cylinder
is connected to said right part of said casting die,
- said multiplying cylinder having a space in
front of a piston thereinside, said space communicating
with said additional cavity by means of a control gate.
12

Description

-- 1
The invention relates to a pressure die-casting method
and finds application in Eoundries for the production of
castings in different materials with high physico-mechanical
characteristics.
The invention also relates to an apparatus to carry out
the method.
In the known pressure die-casting method the melt from a
molten metal reservoir passes via a closed material conduit
and fills the casting mould under the action of a difference
in pressures existing in the melt reservoir and the casting
mould. Filling of the casting mould starts under an ambient
pressure and when the mould is filled up to a preset level
appropriate vacuum is created in the still unfilled space
of the mould over the melt to control the rate of final
mould filling. Upon completion of mould filling the melt
inside crystallizes and the ready casting is removed there-
from.
A drawback of the method is that the melt crystallizes
under the effect of the already created vacuum or low
pressure and therefore it is impossible to have control
over the crystallization process in all sections of the
casting and in particular when components oE an intricate
design are involved. It results in worsening the physico-
mechanical properties of the cast part.
The object of this invention is to create a pressure die-
casting method and apparatus (machine) which allows for
the control of the die-filling and crystallization processes
in any part of the casting die at minimum energy losses
and producing cast components with high physico-mechanical
properties.
,',i~

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According to the present invention there is provided a
pressure die-casting method in which the melt from a
molten metal reservoir is delivered and fills the casting
die under the action oE a difference in pressures created
in the molten metal reservoir and the casting die and when
the melt fills the die it is under the action of vacuum,
ambient or increased gas pressure, characterized by that
after filling the casting die with melt up to a preset
level in the unfilled cavity of the casting die or in one
or several unfilled independent cavities of the die an
additional gas pressure considerably higher than that
acting already in the casting die is created and simul~
taneously this additional gas pressure is equalized by the
counter acting pressure created on the other side of the
casting die.
The abovesaid additional pressure can be maintained at a
constant level until the complete crystallization of melt
in the casting die or continuously increased for the time
from its creation until the completion of crystallization.
The advantages of the method lie in the fact that the
additional gas pressure starts acting on the melt at a
preset time selected in dependence on the configuration
of the concrete casting part and its constructive material
and is created in the casting die. Thus the die-filling
with melt and crystallization of the latter are influenced
at the same time effecting the control over the said two
processes at minimum energy consumptions. All this makes
possible the production of casting components possessing
desired and at same time high physico-mechanical features
independent of their configuration.
According to the present invention, there is also provided

''~J~
- 2a -
an apparatus for pressure die-casting comprising:
- a reservoir
- a casting die made of two-parts and comprising
a cavity, said reservoir being connected to said casting-
die, and said casting-die having an additional cavity,
- a first source of pressure to which said
reservoir is connected,
- a second source of pressure to which said
reservoir is connected,
- a rnultiplying cylinder connected to said cast-
ind die, said multiplying cylinder being also connected
to said additional cavity and to said second source of
pressure.
Preferred embodiments will now be described as examples
without any limitative manner having reference to the
attached drawings, wherein
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Figure 1
A schematic diagram of the machine for the im-
plementation of the method when casting with melt supplied
by means of a difference in gas pressures created in the
casting die and the molten metal reservoir;
Figure 2
An examplary indicator diagram of the delivery
pressure during castin~ as per the diagram on Fig. l;
Figure 3
A schematic diagram of the machine for the im-
plementation of the method in casting under an ambient pressure
in a casting die and with a delivery pressure produced by a
piston;
Figure 4
An indicator diagram of the delivery pressure in
casting as per the diagram on Fig.3;
Figure 5
A flow diagram of casting in the presence of
vacuum in the casting die and the creation of a delivery
pressure in result of a difference in pressures of gaseous
phase;
Figure 6
An indicator diagram of delivery pressure in
casting as per the diagram shown on Fig. 7;
Figure 7
A schematic diagram of the machine for the im-
plementation of the casting method with an increased pressure
in the casting die and a delivery pressure created by the
difference in pressures of gaseous phase;
Figure 8
An indicator diagram of the delivery pressure in
casting as per the diagram on Fig.5.
The machine for the implementation of the method
as per Fig. 1 consists of a molten metal (melt) reservoir 1
- ~r

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connected to the casting die 3 by means of a material feed
conduit 2. The castiny die is made in 2 parts - a lower par~
31 and an upper part 32 forming the casting cavity 4, while
the additional cavities 5 are formed in the upper part 32.
The melt reservoir is connected to a compressed gas source
6 via a valve 7. The qas pressure in the gas source 6 is
Pl which is also the delivery pressure. The melt reservoir 1
is provided with a pressure indicator 8 which is by means of
a transducer 9 and a valve 10 connected to a compressed gas
tank 13 being under a high pressure - P3. A multiplying
cylinder 11 is mounted on the lower part of the die 3 and by
means of a control butterfly valve 12 and a conduit is
connected to the additional cavities 5 on one side and by
means of a conduit via the valve 10 - to the compressed air
tank 13.
The casting process as per this examplary flow
diagram is performed in the following manner: when the melt
is ready for casting a difference between pressures in the
melt reservoir 1 and the casting die 3 (31,32) is created and
the melt starts filling the casting cavity 4 via the material
feed conduit, while in the melt reservoir l - casting die 3
system there could have existed vacuum, ambient or increased
pressure. In the filling process the delivery pressure rises
in result of overcoming the friction forces, the hydraulic
height of melt and the throttling effect of the gaseous
phase when coming out of the vents being gradually and unevenly
filled by melt. When a preset level of melt is reached as
shown with the A-A line and p. "a" of the indicator diagram
(Fig. 2), the delivery pressure Pl changes its character for
instance as a result of the abrupt change in the cross section
of the casting. By means of a signal given by the pressure
indicator 8 to the deliver~ pressure the transducer 9 is
actuated and opens the valve 10 so that the gaseous phase
from the high pressure source 13 is supplied to the unfilled
-- 4
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67~
additional cavities 5 of the casting die 3 and to the multiply-
ing cylinder 11 and the high pressure P3 is established in
the casting die 3. During the movement of the piston in the
multiplying cylinder 11 the molten metal flow from the melt
reservoir 1 is interrupted and the casting die 3 is finally
filled with melt. After the pressure has been taken off and
cooling performed, the ready casting part is removed and the
cycle repeated.
The machine for the implementation of the method
as per Fig. 3 consists of a material cylinder 1 connected via
a riser duct to the casting die 3 comprised of a right part
31 and a left part 32 which define the casting cavity ~ and
the additional cavity 5 (dead head). The material cylinder 1
is connected to a pressure source 6 having a pressure Pl
through a valve 7, a conduit and a power cylinder 18 with
a pressure indicator 8 fitted on it. The power cylinder 18
is connected to the multiplying cylinder 11 one part of which
communicates through a tube with the die cavity 4 and via a
valve 14 with the compressed air tank 13 being under a high
pressure P3. The~pressure indicator 8 is connected to a
tranducer 9 which, in its turn, is connected through a valve
10 to the additional cavity 5 and the multiplying cylinder llo
The communication between the transducer 9 and the additional
cavity 5 is provided with a control gate 12.
According to the diagram shown on Fig. 3 the
casting process runs as follows:
Characteristics of the casting part: A car piston
in aluminium-silicon alloy having a skirt with a 6 mm thick
wall; a reinforcing ring in the lower portion of the skirt;
bosses in the zones of piston bolt seats having a thickness
of 20 mm and a bottom wall thickness of 25 mm.
Casting is performed in a two-cavity metal casting
die 3 with a split wedge core for the central hole and cores
for the radial holes. The air vents, the riser duct and the
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672~:
dead heads 5 are formed in the die 3.
The gas passing from the compressed air tank 13
via an opened valve 14 into the multiplying cylinder ll creates
a gas pressure of 60 MPa. Then the valve 14 is closed and a
portion of melt is poured into the material cylinder 1. In
the power cylinder 18 and the multiplying cylinder ll a
hydraulic pressure is provided from the tank 6 at an opened
valve 7. The piston of the power cylinder 18 moves the melt
filling the cavity of the die 3. When filling the additional
cavities 5 of the die 3 the delivery pressure Pdel (Fig. 4)
read by the pressure indicator 8 changes and after having
filled a part of the dead heads 5, it changes its character
(p- "a", Fig. 4) and upon a signal by the pressure indicator
8 the transducer 9 is being actuated to open the valve 10
starting the piston of the multiplying cylinder 11 and a
pressure of 300 ~Pa is being exerted on the dead heads 5.
Such pressure is maintained until the completion of the
crystallization process in the casting part and thereafter it
is removed and the part is taken out of the die. The casting
part obtained after the appropriate heat treatment has the
following characteristics: ~B= 32 - 36.105 N/m2;
S= 27 - 30.105 N/m2; ~ > 3~; ~B = 120 - 140u
The machine for the implementation of the method
as per Fig. 5 consists of a molten metal (melt) reservoir 1
communicating via a material feed conduit ~ with the casting
die 3 that comprises two parts - the lower part 31 and the upper
part 32 with the cavity 4 in-between. In the upper part 32
there are additional cavities 5 (dead heads) provided. The
melt reservoir 1 is connected with the gas pressure source
6 at a pressure Pl through a valve 7. The melt reservoir 1
and the space of the casting die 3 are connected by a pressure
indicator 8 provided with a transducer 9. The transducer 9
via a valve 10 communicates with the high pressure tank 13
at a pressure P3, the latter being connected via the said
-- 6
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valve 10 to the multiplying cylinder 11 comrnunicating with the
lower part 31 of the die. The space of the multiplying
cylinder 11 in front of the piston communicates with the
additional cavities 5 of the casting die 3 through a control
gate 12. The space of the casting die 3 is connected with
the vacuum tank 17 by means of a tube and a valve 16.
According to the diagram shown on Fig. 5 the
casting process is carried out in the following way:
Charateristics of the casting part: a car sus-
pension component in aluminium alloy with a complex combinationof thin and thick walls in the thickness range from 4 to
25 mm. The bosses are concentrated in three places at a
distance from the central hole ranging 300 - 400 mm. A
complex ribbed design with a rib relief up to 90 mm.
The casting is performed in a metal casting die
of two parts located in a sealed chamber.
The split line of the parts 31, 32 has a complex
configuration. The air vents are made in the casting die,
while the dead heads are over the bosses of the casting part.
The cavities of the casting part in the space between the ribs
are formed by inserts and between them there are also vents.
prior to commencement of casting in the chamber incorporating
the casting die 3 there is created vacuum of 0,1 - 0,2 MPa
from the source 17 at an opened valve 16. A difference between
pressures in the melt reservoir 1 and the casting die 3 is
produced to result in the initial filling of the cavity 4 for
the casting part. When the melt blocks the vents of the
split planes, the delivery pressure changes its character
and by means of a signal from the indicator 8 the transducer 9
which opens the valve 10 is actuated.
A high pressure equalized by the piston of the
multiplying cylinder 11 is established in the cavity of the
casting die 3. Such pressure is maintained until the com-
pletion of the crystallization process in the casting part
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and thence it is removed and the casting part is taken out of
the die. The vacuum is maintained only until the complete
filling of the casting die 3 with melt.
The machine for the implementation of the method
as per Fig. 7 consists of a molten metal (melt) reservoir 1
connected via a material feed conduit 2 with the casting die
3 comprising a left part 31 and a right 32 while the casting
cavity 4 is formed in-between. The additional cavities (dead
head) 5 are formed in the left part 31. The melt reservoir 1
is connected to the pressure source 6 with a pressure Pl by
means of a valve 7. The pressure source 6 communicates also
with the casting die 3 via a valve 15. To the melt reservoir
there is fitted a pressure indicator ~ provided with a transducer 9
9 which via a valve 10 is connected to the high pressure
tank 13 having a pressure P3. The high pressure tank 13 is
connected with a multiplying cylinder 11 connected to the
right part 32. The space in front of the piston of the
multiplying cylinder 11 communicates via a pipe conduit and
a control gate 12 with the additional cavities 5.
According to the diagram shown on Fig. 7 the
casting is performed as follows:
Characteristics of the casting part: A ribbed
component designed to operate under the effect of water
vapours at 150 and a pressure of 10 MPa at the requirements
for ~B= 30 - 32.105 N/m2 and ~S > 20%.
Casting is carried out in a two-cavity metal die with an
elastic seal. Between the seal ring and the working cavity
of the die there is a deep and wide channel made which
communicates with the working cavity of the die by means of
vents. The vents and the space for the dead head are formed
in the casting die.
The melt being a technically pure grade of Zn is
supplied to the melt reservoir 1 where the melt is agitated
by means of nitrogen under a pressure of lO.105 N/m and
thereafter in the melt reservoir 1 - casting die 3 system a
pressure of 10.105 N/m2 is
- 7a -

established. A pressure diferential is created and the
melt fills the casting die 3 up to the line A-A (p. "a"
on Fig.8) and the delivery pressure changes its nature.
Upon a signal from the pressure indicator 8 the trans-
ducer 9 is actuated to open the valve 10 and a pressure
of 96.105 N/m2 is established in the unfilled cavity 5
of the casting die 3. This pressure is equalized by the
pressure in the multiplying cylinder 11. In movement of
the piston of the multiplying cylinder 11 the incoming
flow of melt from the melt reservoir 1 is shut off and
final filling of the casting die 3 is performed at a high
pressure. The crystallization of the melt completed, the
pressure is removed from the casting die 3 and the latter
is cooled and taken out.