Note: Descriptions are shown in the official language in which they were submitted.
i~22i52
P-356
TITLE
A method and assembly for hot consolidating
materials.
TECHNICAL FIELD
The subject invention is used for consolidating
material of metallic and nonmetallic powder compositions
and combinations thereof to form a predetermined densified
compact. Consolidation is usually accomplished by evacu-
10 ating a container and filling the container with a powder
to be consolidated and thereafter hermetically sealing the
container. Pressure is then applied to the filled and
sealed container to subject the powder to pressure.
Typically, heat is also applied to heat the powder to a
15 compaction temperature. The combination of heat and
pressure facilitates consolidation of the powder.
;
BACKGROUND ART
It is well-known to place a hermetically sealed
20 container with the powder therein in an autoclave or hot
isostatic press where it is subjected to heat and gas
pressure.
Because of the expense and limitations of an
autoclave or hot isostatic press, there have been
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significant developments made wherein the powder to be
compacted is encapsulated in a substantially fully dense
and incompressible container providing a pressure-
transmitting medium which maintains its configurational
5 integrity while being handled both at ambient temperatures
and at the elevated compaction temperatures, yet becomes
fluidic and capable of plastic flow when pressure is
applied to the entire exterior surface thereof to hydro-
statically compact the powder. Typically, the powder is
10 hermetically encapsulated within the pressure-transmitting
medium which is thereafter heated to a temperature suf-
ficient for compaction and densification of the powder.
After being sufficiently heated, the pressure-transmitting
medium with the powder therein may be placed between two
15 dies of a press which are rapidly closed to apply pressure
to the entire exterior of the pressure-transmitting
medium. The pressure-transmitting medium, at least im-
mediately prior to a selected predetermined densification,
must be fully dense and incompressible and capable of flow
20 so that the pressure transmitted to the powder is hydro-
static and, therefore, from all directions, i.e~, omni-
directional. After the material is densified to the
desired degree, the pressure-transmitting medium defining
the container must be removed from the compacted material
25 and in so doing the integrity of the pressure-transmitting
medium is lost whereby either the pressure-transmitting
medium is no longer usable or must be completely recycled
to fabricate a new container.
SUMMARY OF THE INVENTION AND ADVANTAGES
The subject invention is for consolidating material
of metallic and nonmetallic compositions and combinations
thereof to form a densified compact of a predetermined
density wherein a quantity of such material which is less
35 dense than the predetermined density is heated and dis-
posed in a cavity in a pressure-transmitting medium to
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which external pressure is applied to the entire exterior
of the medium to cause a predetermined densification of
the material by hydrostatic pressure applied by the medium
in response to the medium being substantially ~ully dense
and incompressible and capable of elastic flow at least
just prior to the predetermined densification. The
invention is characterized by utilizing an elastomeric for
the pressure-transmitting medium and applying pressure
through the elastomeric medium defined by a first
component of elastomeric medium disposed within a pot die
cavity and a second component of the elastomeric medium
acted upon by a ram movable into and out of the pot die
cavity in close sliding engagement therewith and
positioning the first and second elastomeric components so
that the ram enters the cavity of the pot die prior to the
first and second elastomeric components being compressed
between said ram and pot die, heating the material prior
to placement in the compaction cavity defined by the first
and second components of the elastomeric medium
encapsulating the material in at least a portion of a
formed and self-sustaining thermal insulating barrier
means before placing the heated material into the
compaction cavity, placing the thermal barrier means with
the heated material encapsulated therein into the
compaction cavity of the elastomeric medium, and applying
pressure to the medium and crumbling the barrier means
into particulate surrounding the material to limit heat
transfer between the material and the elastomeric medium,
successively opening and closing the first and second
components of elastomeric medium upon opening and closing
of the ram and pot die in a press to successively form a
plurality of densified compacts with a plurality of formed
barrier means.
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BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the present invention will be
readily appreciated as the same becomes better understood
by reference to the following detailed description when
considered in connection with the accompanying drawings
wherein:
FIGURE 1 is a cross-sectional view of an assembly
utilized in accordance with the subject invention disposed
in the open position;
FIGURE 2 is a cross-sectional view similar to FIGURE
1 showing the assembly in a closed position;
FIGURE 3 is a fragmentary cross-sectional view taken
along line 3-3 of FIGURE 2; and
FIGURE 4 is a fragmentary view of a portion of the
exterior surface of a seal utilized in the assembly of the
subject invention.
DESCRIPTION OF THE INVENTION
The subject invention may be utilized for
consolidating various metallic powders and nonmetallic
powders, as well as combinations thereof, to form a
densified compact. In accordance with the invention, the
degree of density of the powder is increased to a
predetermined or desired density which may be full density
or densification or less than full density or
densification.
The invention relates to a method for consolidating
material of metallic and nonmetallic compositions and
combinations thereof to form a densified compact of a
predetermined density wherein a quantity of such material
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which is less dense than the predetermined final density
is encapsulated in a pressure-transmitting medium to which
external pressure is applied to the entire exterior of the
medium to cause a predetermined densification of the en-
5 capsulated material by hydrostatic pressure applied by themedium in response to the medium being sustantially fully
dense and incompressible and capable of elastic flow,
i.e., fluidic, at least just prior to the predetermined
densification. In other words, the medium transmits
10 pressure hydrostatically like a liquid omnidirectionally
about the material for compaction thereof.
As the invention is illustrated, a quantity of less
than fully dense powder 10 ~ills and is encapsulated
within a container 12. The container 12 is evacuated as
15 by a vacuum through a tube (not shown) and then is filled
with the powder 10 under vacuum through the tube. After
filling, the tube is sealed to hermetically seal the con-
tainer 12 with the powder 10 under a vacuum therein. The
container 10 is a thin-walled and preferably of a sheet
20 metal material. The container 12 may be filled and sealed
in accordance with the teachings of United States Patent
4,229,872 granted October 28, 1980 and assigned to the
assignee of the subject invention.
The container 12 is circular in cross section to
25 define a cylinder and has a fill tube (not shown) extend-
ing from one end thereof. It will be understood, however,
that the configuration of the container 12 will depend
upon the desired configuration of the end part or compact.
As illustrated, an assembly for implementing the
30 subject invention includes a pot die 14 and a ram 16 which
include attachment points 18 for attaching alignment keys
for aligning the pot die 14 and ram 16. The pot die 14
and the ram 16 also include bores 20 for receiving
attaching bolts or pins to attach the pot die 14 and ram
35 16 to a press which may be one of any of a number of
well-known types. The ram 16 and pit die 14 are aligned
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during the opening and closing of the press between the
open position shown in Figure 1 and the closed position
shown in FIGURE 2.
A pressure-transmitting medium, comprising first and
5 second elastomeric components 22 and 24, defines a cavity
for encapsulating the material to be consolidated. The
pot die 14 is made of an incompressible material such as
steel and includes a pot die cavity 26. In a similar
fashion, the ram 16 iS made of an incompressible material
10 such as steel and includes a ram-cavity 28 therein. The
ram 16 includes a raised flange or ridge 30 surrounding
the ram-cavity 28. The pot-die cavity 26 has peripheral
surfaces for receiving and sliding engagement with the
exterior surfaces of the raised flange 30 of the ram 16.
15 In other words, the interior surfaces of the cavity 26 in
the pot die 14 are aligned with the exterior surfaces of
the flange 30 of the ram 16 so that they are in close
sliding engagement with one another as the pot die 14 and
ram 16 are closed. The first component 22 of the
20 elastomeric medium is retained in the pot-die cavity 26 as
by being wedged therein or having small amounts of
adhesive securing the elastomeric component to the cavity
26. In a similar fashion, the second elastomeric
component 24 is retained in the ram-cavity 28. The first
25 and second elastomeric components 22 and 24 define a
cylindrical cavity for surrounding the material 10 for
compaction thereof. The elastomeric components 22 and 24
may, in addition to natural rubber, consist of elastomers
such as neoprene, polysiloxane elastomers, polyurethane,
30 polysulfide rubber, polybutadiene, buna-S, etc. The
elastomeric medium making up the components 22 and 24 is
elastic in that it may be compressed and yet returns to
its original configuration. However, after the
elastomeric medium defining the components 22 and 24 is
35 compressed to a certain degree, it becomes substantially
incompressible, yet fluidic, i.e., capable of elastic
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flow, so that at the point of compaction and the desired
densification of the powder 10, it hydrostatically applies
pressure omnidirectionally about the container 12 to
compact the powder 10 therein. The container 12 is of a
5 material which is thin-walled and reduces in volume to
compact the powder lO.
The powder 10 is heated to an elevated temperature
for facilitating densification and compaction of the
powder 10. In order to protect the elastomeric medium
10 defining the components 22 and 24, a thermal insulating
barrier means establishes a thermal barrier between the
powder material 10 and the elastomeric medium 22 and 24
prior to applying pressure to the medium 22 and 24 by the
closure of the pot die 14 and ram 1~ to limit the heat
15 transfer between the material 10 and the elastomeric
medium 22 and 24. The thermal insulating barrier means
includes a first thermal insulating jacket 32 completely
surrounding the container 12 for limiting the heat loss
from the material 10 and a second thermal insulating
20 jacket 34 surrounding the first jacket 32 for protecting
the elastomeric components 24 and 22 from heat emanating
from the first jacket 32.
In accordance with the subject invention, the jackets
32 and 34 are made of a ceramic material having a very low
25 thermal conductivity. In addition, the material of which
the jackets 32 and 34 are made is fluidic or capable of
flow at least just prior to the desired compaction of the
powder 10 as pressure is applied thereabout hydro-
statically through the elastomeric components 22 and 24.
30 By analogy, the material of the jackets 32 and 34 may flow
in the manner of quicksand just prior to compaction. In
the preferred mode, the container 12 has the first jacket
32 cast thereabout in a mold so that the jacket 32
completely encapsulates the container 12 and is a
35 homogeneous material. The first jacket 32 with the
container 12 and the material therein is heated to an
'
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elevated temperature sufficient for compaction. During
this heating, the jacket 32 becomes heated. Thereafter,
the jacket 32, with the container 12 and the material 10
therein, is placed within the second jacket 34 within the
5 cavity defined by the elastomeric components 22 and 24.
The second jacket 34 is made of two complementary sections
which mate together to completely encapsulate and surround
the first jacket 32. The second jacket 34 is also fluidic
or capable of flow just prior to the desired densification
10 of the powder 10. Once the heated material 10 within the
container 12 which is, in turn, encapsulated in the first
jacket 32 is placed within the second jacket 34 as
illustrated in FIGURE 1, the press closes to close the pot
die 14 and ram 16 whereby the flange 30 of the ram 16
15 enters the cavity 26 of the pot die 14. It is important
to note that the flange 30 enters the cavity 26 of the pot
die 14 before the elastomeric components 22 and 24 contact
one another and are compressed to create hydrostatic
pressure as they become incompressible and fluidic for
20 transmitting hydrostatic pressure omnidirectionally
against the second jacket 34 which, in turn, transmits the
hydrostatic pressure through the jacket 32 and the
container 12 to compact and densify the powdered metal 10.
To compensate for differences in coefficients of thermal
25 expansion, either or both of the jackets 32 and 34 may be
made of a ceramic having reinforcing fibers therein which
allow some contraction or expansion of the basic materials
making up the jackets 32 or 34. In other words, either
one of the jackets 32 and 34 may have fibers dispersed
30 therein for reinforcement. Further, the jackets 32 and 34
may be made of a crumbling material which may be crushed
to become incompressible, but yet fluidic enough to
transmit the pressure hydrostatically from the elastomeric
components 22 and 24 to the container 12 and, thus, to the
35 powdered metal 10.
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It is important that the flange 30 of the ram 16
enter the cavity 26 of the pot die 14 prior to the elasto-
meric components 22 and 24 engaging one another to control
the movement of the elastomeric components 22 and 24.
5 Further to this end, a seal 36 of a harder material than
the elastomeric medium defining the components 22 and 24
is disposed within and below the upper extremity of the
cavity 26 of the pot die 14 so that after the flange 30 of
the ram 16 enters the pot die 14 and applies pressure to
10 the elastomeric components 22 and 24, the seal 36 is
forced into sealing engagement with the interior surfaces
of the cavity 26 in the pot die 14 at the juncture thereof
with the exterior surface of the flange 30 of the ram 16
to prevent leakage of the elastomeric components 22 and 24
15 between the ram 16 and the pot die 14. The seal 36 is of
a higher durometer than the elastomeric components 22 and
24 and, therefore, is less capable of plastic flow albeit
the seal material 36 is capable of plastic flow.
Once the flange 30 of the ram 16 enters the cavity 26
20 of the pot die 14, the elastomeric components 22 and 24
engage one another and begin to compress to a point at
which they become incompressible and convey pressure
hydrostatically in an omnidirectional fashion to compact
the powdered metal 10. During the initial compression of
25 the elastomeric components 22 and 24, they move or slide
: relative to the surfaces of the cavities in which they are
disposed in the pot die 14 and ram 16, respectively.
Accordingly, the components 22 and 24, as well as the seal
36, include a plurality of lubrication grooves 38 and 40,
30 respectively, in the exterior surfaces thereof to facili-
tate movement relative to the adjacent supporting surface
of the cavities in which they are disposed. Preferably, a
lubricant is disposed within the grooves 38 and 40 to
allow the material to compress and slide relative to the
~35 adjacent surfaces. As illustrated in FIGURE 2, upon full
:~compression of the components, the grooves are diminished
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in size so as to be imperceivable, yet the grooves exist
to trap incompressible lubricant therein during full
compression.
In accordance with the invention, the powdered metal
5 10 fills a thin-walled container 12 which is, in turn,
encapsulated within a first thermal insulating jacket 32
as by having the jacket 32 cast thereabout, after which
they are heated to an elevated temperature sufficient for
compaction of the powder 10. Thereafter, a lower section
10 of the second jacket 34 may be disposed within a cavity in
the elastomeric component 22 of the pot die 14 and the
first jacket 32 with the powder therein disposed within
the lower section 34 of the outer jacket. The upper half
or section of the second jacket 34 is then disposed over
lS the heated inner or first jacket 32 and the ram and pot
die are moved together to the position shown in FIGURE 2
to densify and compact the powder into a densified compact
10'. The elastomeric medium defining the components 22
and 24 may initially be compressible, but upon reaching a
20 certain point of applied pressure becomes imcompressible
so as to hydrostatically transmit pressure in an
omnidirectional fashion entirely about the jackets 32 and
34 to the powder 10 to compact and densify the powder into
the compact 10' of the desired densification. The pot die
25 14 and ram 16 may be opened to allow the elastomeric
components 22 and 24 to return to their precompressed
shape and to remove the compact 10' so that thereafter the
container 10 and the jackets 32 and 34 may be removed to
expose the compact 10'. Normally, the jackets 32 and 34
30 will be disposable and new jackets would be utilized on
successive opening and closing of the pot die 14 and ram
16 for successively forming compacts 10'.
It will be appreciated that in many circumstances
~` only one thermal insulating jacket may be utilized between
`35 the heated powdered material 10 and the elastomeric com-
ponents 22 and 24. Additionally, the thicknesses of the
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thermal insulating barrier means may vary depending on the
sizes, configurations, masses, etc. of the powder 10 to be
compacted and densified.
The invention has been descr bed in an illustrative
5 manner, and it is to be understood that the terminology
which has been used is intended to be in the nature of
words of description rather than of limitation.
Obviously, many modifications and variations of the
present invention are possible in light of the above
10 teachings. It is, therefore, to be understood that within
the scope of the appended claims wherein reference
numerals are merely for convenience and are not to be in
any way limiting, the invention may be practiced otherwise
than as specifically described.
