U.S. patent application number 14/751855 was filed with the patent office on 2016-05-05 for dual vacuum induction melting & casting.
This patent application is currently assigned to RETECH SYSTEMS LLC. The applicant listed for this patent is RETECH SYSTEMS LLC. Invention is credited to ROBERT COOK, JOHN MCKELLAR, MIKE MULALLEY, THOMAS WOOLEY.
Application Number | 20160121394 14/751855 |
Document ID | / |
Family ID | 55851599 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160121394 |
Kind Code |
A1 |
COOK; ROBERT ; et
al. |
May 5, 2016 |
DUAL VACUUM INDUCTION MELTING & CASTING
Abstract
A furnace system for melting and casting metals, alloys, and
superalloys and a related method. A melt chamber of the furnace
system is configured and arranged to include at least two melt
boxes, thereby increasing the volume of alloy charge that can be
rendered molten during a single furnace heating cycle. Accordingly,
a number of ceramic casting molds equal to the number of melt boxes
can be used to form castings following a single furnace heating
cycle. The ceramic casting molds can be pre-heated in an external
oven before being introduced to the mold or loading chamber of the
furnace system. The throughput of the furnace system is increased
by the ability to pour more than one casting per alloy charge
melting cycle.
Inventors: |
COOK; ROBERT; (UKIAH,
CA) ; WOOLEY; THOMAS; (UKIAH, CA) ; MCKELLAR;
JOHN; (UKIAH, CA) ; MULALLEY; MIKE; (UKIAH,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RETECH SYSTEMS LLC |
UKIAH |
CA |
US |
|
|
Assignee: |
RETECH SYSTEMS LLC
UKIAH
CA
|
Family ID: |
55851599 |
Appl. No.: |
14/751855 |
Filed: |
June 26, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62072635 |
Oct 30, 2014 |
|
|
|
Current U.S.
Class: |
164/493 ;
164/151.4; 164/513 |
Current CPC
Class: |
B22D 2/006 20130101;
B22D 47/00 20130101; B22D 21/025 20130101; B22D 27/15 20130101 |
International
Class: |
B22D 47/00 20060101
B22D047/00; B22D 21/02 20060101 B22D021/02; B22D 33/00 20060101
B22D033/00; B22D 41/00 20060101 B22D041/00; B22D 2/00 20060101
B22D002/00; B22D 27/15 20060101 B22D027/15 |
Claims
1. A vacuum induction casting apparatus, comprising: a loading
chamber, configured to receive a casting mold; a melt chamber,
configured to concurrently house a first melt box and a second melt
box; an interlock mechanically coupled to both the loading chamber
and the melt chamber; a loading mechanism, configured to move the
casting mold into and out of the melt chamber through the interlock
to a casting position; and a vacuum system coupled to both the melt
chamber and to the loading chamber.
2. The vacuum induction casting apparatus according to claim 1,
wherein the loading mechanism is a loading elevator configured to
reciprocally move the casting mold vertically through the
interlock.
3. The vacuum induction casting apparatus according to claim 1,
wherein the loading mechanism is a platen configured to
reciprocally move the casting mold horizontally through the
interlock.
4. The vacuum induction casting apparatus according to claim 1,
further comprising a charge temperature sensor system coupled with
the melt chamber and configured to measure temperatures of one or
more molten charges in either or both of the first melt box and the
second melt box.
5. The vacuum induction casting apparatus according to claim 1,
further comprising a mold temperature sensor system coupled with
the melt chamber and configured to measure a temperature of a mold
within the casting mold.
6. The vacuum induction casting apparatus according to claim 1,
wherein the vacuum system separately controls pressure within the
melt chamber and the loading chamber.
7. The vacuum induction casting apparatus according to claim 1,
wherein the vacuum system further comprises a first vacuum system
and a second vacuum system atmospherically separate from each
other, wherein the first vacuum system is coupled to the melt
chamber and wherein the second vacuum system is coupled to the
loading chamber.
8. The vacuum induction casting apparatus according to claim 1,
wherein the apparatus is further configured to allow for the melt
chamber to load an alloy charge into either or both of the first
melt box and the second melt box concurrent with the loading
mechanism in a position outside of the melt chamber.
9. The vacuum induction casting apparatus according to claim 1,
further comprising a third melt box.
10. The vacuum induction casting apparatus according to claim 9,
further comprising a fourth melt box.
11. A method of forming castings, comprising: loading a first alloy
charge into a first melt box and a second alloy charge into a
second melt box within a melt chamber of a furnace system; melting
the first and second alloy charges within the first melt box and
the second melt box to be molten; pre-heating an initial casting
mold and pre-heating a subsequent casting mold; loading the initial
casting mold into a loading chamber of the furnace system; moving
the initial casting mold to a casting position within the melt
chamber; pouring the molten first alloy charge from the first melt
box into the initial casting mold; moving the initial casting mold
out of the melt chamber and removing the initial casting mold from
the furnace system; loading the subsequent casting mold into the
loading chamber of the furnace system; moving the subsequent
casting mold to the casting position within the melt chamber;
pouring the molten second alloy charge from the second melt box
into the subsequent casting mold; and moving the subsequent casting
mold out of the melt chamber and removing the subsequent casting
mold from the furnace system.
12. The method according to claim 11, further comprising: reducing
the pressure in the melt chamber; and reducing the pressure in the
loading chamber.
13. The method according to claim 12, further comprising: reducing
the pressure in the melt chamber to about 5 mTorr; and reducing the
pressure in the loading chamber to about 100 mTorr.
14. The method according to claim 11, wherein the initial casting
mold and the subsequent casting mold are each pre-heated to a
temperature of about 800.degree. C. to about 1,000.degree. C.
15. The method according to claim 11, wherein the melt chamber is
raised to a temperature of about 1,300.degree. C. to melt either or
both of the first and second alloy charges within the first melt
box and the second melt box.
16. The method according to claim 11, wherein a casting mold
removed from the furnace system is allowed to cool such that a
casting in the casting mold has an equiaxed structure.
17. The method according to claim 11, further comprising reloading
an alloy charge into either or both of the first melt box and the
second melt box after either the initial casting mold or the
subsequent casting mold is moved out of the melt chamber.
18. The method according to claim 11, further comprising: loading a
third alloy charge into a third melt box within the melt chamber of
the furnace system; melting the third alloy charge with the first
and second alloy charges to be molten; pre-heating a third casting
mold; following removal of the subsequent casting mold, loading the
third casting mold into the loading chamber of the furnace system;
moving the third casting mold to a casting position within the melt
chamber; pouring the molten third alloy charge from the third melt
box into the third casting mold; moving the third casting mold out
of the melt chamber and removing the third casting mold from the
furnace system.
19. The method according to claim 18, further comprising: loading a
fourth alloy charge into a fourth melt box within the melt chamber
of the furnace system; melting the fourth alloy charge with the
first and second alloy charges to be molten; pre-heating a fourth
casting mold; following removal of the third casting mold, loading
the fourth casting mold into the loading chamber of the furnace
system; moving the fourth casting mold to a casting position within
the melt chamber; pouring the molten third alloy charge from the
fourth melt box into the fourth casting mold; moving the fourth
casting mold out of the melt chamber and removing the fourth
casting mold from the furnace system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S.
Provisional Application No. 62/072,635 entitled "DUAL VACUUM
INDUCTION MELTING & CASTING", filed on Oct. 30, 2014, the
disclosure of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a system, apparatus, and
method of melting and casting metals in a controlled atmospheric
environment, such as those that use vacuum induction melting. The
system, apparatus, and method is particularly useful for high
temperature metals, alloys, and superalloys, including alloys used
in the aerospace industry such as nickel-chromium alloys.
BACKGROUND OF THE INVENTION
[0003] The casting of metal, alloy, and superalloy parts often
requires a process with specific, controllable temperature and
pressure requirements. Superalloys generally refer to group of
alloys used in turbosuperchargers, aircraft turbine engines, gas
turbines, rocket engines, chemical, and petroleum plants that
require high performance retaining their structural strength at
elevated temperatures (e.g. 650.degree. C. and greater) over long
exposure times. The versatility of superalloys stems from a
combination of high strength with good low-temperature ductility
and excellent surface stability. Apparatus for melting and casing
metals, alloys, and superalloys into molds to thereby make
corresponding parts can be complicated and therefore requires a
minimum amount of time to accomplish the casting.
[0004] Typically in the industry, in order to increase throughput,
doubling or further increasing casting throughput and capacity
requires installation of a second complete furnace, which further
requires its own support equipment including, but not limited to:
decking, a melt chamber, a mold chamber, a vacuum system, a water
cooling system, a control system, and the like. Further, and
additional external mold handling pathway would be required for the
second furnace. Accordingly, apparatus and processes for melting
and casing metals, alloys, and superalloys as known in the industry
can be limited in throughput and production volume, or can incur a
greater cost and complexity related to the use of additional
complete furnaces.
BRIEF SUMMARY OF THE INVENTION
[0005] The following presents a simplified summary of some
embodiments of the invention in order to provide a basic
understanding of the invention. This summary is not an extensive
overview of the invention. It is not intended to identify key or
critical elements of the invention or to delineate the scope of the
invention. Its sole purpose is to present some embodiments of the
invention in a simplified form as a prelude to the more detailed
description that is presented later.
[0006] For at least the reasons given above, it is desirable to
design a melting and casing apparatus for metals, alloys, and
superalloys having a throughput or production volume that is
increased relative to known apparatus and processes. Further, it is
desirable to control the heating of molten metal or alloys, as well
as the heating of a mold, to make the overall melting and casing
apparatus design more effective, feats which have heretofore not
been accomplished with known hearths in the industry.
[0007] In embodiments, the present disclosure provides for a vacuum
induction casting apparatus that can include a loading chamber
configured to receive a casting mold; a melt chamber, configured to
concurrently house a first melt box and a second melt box; an
interlock mechanically coupled to both the loading chamber and the
melt chamber; a loading mechanism, configured to move the casting
mold into and out of the melt chamber through the interlock to a
casting position; and a vacuum system coupled to both the melt
chamber and to the loading chamber.
[0008] In some aspects, the loading mechanism can be a loading
elevator configured to reciprocally move the casting mold
vertically through the interlock. In other aspects, the loading
mechanism can be a platen configured to reciprocally move the
casting mold horizontally through the interlock. In further
aspects, the vacuum induction casting apparatus further can include
a charge temperature sensor system coupled with the melt chamber
and configured to measure temperatures of one or more molten
charges in either or both of the first melt box and the second melt
box. In some implementations, the vacuum induction casting
apparatus can further include a mold temperature sensor system
coupled with the melt chamber and configured to measure a
temperature of a mold within the casting mold. In some aspects, the
vacuum system separately controls pressure within the melt chamber
and the loading chamber. In other aspects, the vacuum system can
further include a first vacuum system and a second vacuum system
atmospherically separate from each other, where the first vacuum
system is coupled to the melt chamber and where the second vacuum
system is coupled to the loading chamber. In further aspects, the
vacuum induction casting apparatus is further configured to allow
for the melt chamber to load an alloy charge into either or both of
the first melt box and the second melt box concurrent with the
loading mechanism in a position outside of the melt chamber. In
further embodiments, the vacuum induction casting apparatus can
include a third melt box and/or a fourth melt box.
[0009] In embodiments, the present disclosure provides for a method
of forming castings that includes: loading a first alloy charge
into a first melt box and a second alloy charge into a second melt
box within a melt chamber of a furnace system; melting the first
and second alloy charges within the first melt box and the second
melt box to be molten; pre-heating an initial casting mold and
pre-heating a subsequent casting mold; loading the initial casting
mold into a loading chamber of the furnace system; moving the
initial casting mold to a casting position within the melt chamber,
pouring the molten first alloy charge from the first melt box into
the initial casting mold; moving the initial casting mold out of
the melt chamber and removing the initial casting mold from the
furnace system; loading the subsequent casting mold into the
loading chamber of the furnace system; moving the subsequent
casting mold to the casting position within the melt chamber;
pouring the molten second alloy charge from the second melt box
into the subsequent casting mold; and moving the subsequent casting
mold out of the melt chamber and removing the subsequent casting
mold from the furnace system.
[0010] In some implementations, the method further includes,
reducing the pressure in the melt chamber and reducing the pressure
in the loading chamber. In some specific aspects, the method can
include reducing the pressure in the melt chamber to about 5 mTorr
and reducing the pressure in the loading chamber to about 100
mTorr. In other implementations, the initial casting mold and the
subsequent casting mold can each be pre-heated to a temperature of
about 800.degree. C. to about 1,000.degree. C. In further
implementations, the melt chamber can be raised to a temperature of
about 1,300.degree. C. to melt either or both of the first and
second alloy charges within the first melt box and the second melt
box. In some aspects, the casting mold can be removed from the
furnace system and allowed to cool such that a casting in the
casting mold has an equiaxed structure. In other aspects, the
method can include reloading an alloy charge into either or both of
the first melt box and the second melt box after either the initial
casting mold or the subsequent casting mold is moved out of the
melt chamber. In further embodiments, the method can include used
of a third melt box and/or a fourth melt box in order to allow for
casting of a third and/or fourth casting mold as part of a
processing cycle.
[0011] For a more complete understanding of the nature and
advantages of the present invention, reference should be made to
the ensuing detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Illustrative aspects and embodiments are described in detail
below with reference to the following drawing figures.
[0013] FIG. 1 is a flowchart illustrating a process for casting a
metal or alloy mold in combination with a dual melt box melt
chamber, in accordance with some embodiments of the present
disclosure.
[0014] FIG. 2 is a schematic diagram of a connected mold chamber
and melt chamber coupled with an atmospheric and vacuum control
system, in accordance with some embodiments of the present
disclosure.
[0015] FIG. 3 is a schematic diagram of a furnace system having a
connected mold chamber and melt chamber, in accordance with some
embodiments of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Throughout this description for the purposes of explanation,
numerous specific details are set forth in order to provide a
thorough understanding of the many embodiments disclosed herein. It
will be apparent, however, to one skilled in the art that the many
embodiments may be practiced without some of these specific
details. In other instances, well-known structures and devices are
shown in diagram or schematic form to avoid obscuring the
underlying principles of the described embodiments.
[0017] Embodiments of the present disclosure provide for a vacuum
induction melting and casting system and related method for
efficiently and effectively casting metal, alloy, and superalloy
parts. Vacuum induction casting (alternatively referred to as
vacuum pressure casting) can be considered a subset of investment
casting or lost-wax casting, where a ceramic mold (alternatively
referred to as the investment, shell, or casting mold) produced by
investment casting is placed within a melt chamber, the pressure in
the chamber is reduced to vacuum (or a sufficiently low pressure),
and metal or alloy is poured into the ceramic mold. By casting the
metal or alloy at vacuum (or a sufficiently low pressure), the
porosity of the casting can be reduced and the overall strength of
the casting is improved. Once the casting of metal or alloy has
cooled, the ceramic mold is released from the casting by direct
physical force (e.g. hammering), media blasting, vibration,
waterjet cutting, or chemical solvents. Any excess portions of the
casting or sprue can be cut or otherwise removed from the
casting.
[0018] Investment casting involves producing a master pattern,
forming a master die (alternatively referred to as a mold or mould)
based on the master pattern, producing a secondary pattern (which
can be made of wax, polymers, frozen mercury, or other materials
known in the industry) based on the master die. The secondary
pattern, which can be combined with other secondary patterns, is
then used as the base for an investment which is formed by coating,
stuccoing, and hardening a ceramic around the secondary mold,
thereby forming a ceramic mold. The coating, stuccoing, and
hardening cycle is repeated as necessary until the ceramic mold is
of desired dimensions. The ceramic mold can then be dried and/or
heated to remove traces of the secondary pattern material remaining
on the ceramic mold and to sinter the ceramic mold. The ceramic
mold can then be used for casting according to the vacuum process
disclosed herein.
[0019] Embodiments of the present disclosure can improve the
throughput, production, and yield for casting metals, alloys, or
superalloys in ceramic molds through a vacuum induction process. In
particular, a vacuum induction process can use a furnace having a
melt chamber with two (2) melt boxes. Furnace melt chambers as
known in the industry typically have a single melt box per melt
chamber, due to restrictions of size, melt box shape, and apparatus
for tilting or moving the melt box within the melt chamber. In
aspects, a furnace of the present disclosure utilizes two
independent melt box and crucible tilt assemblies within a single
melt chamber, where both melt boxes cast into molds received from a
single mold loading chamber. This design can provide advantages
including, but not limited to: providing flexibility and
improvements of time cycle scheduling for mold castings; providing
flexibility and improvements of time cycle scheduling for the
furnace; reducing the overall facility footprint (i.e. reducing the
number of furnaces needed to achieve a comparable throughput);
providing flexibility for utilization of operators running the
furnace; and decreasing the idle time of the furnace and any
related subassemblies.
[0020] The configuration of a furnace having two melt boxes within
a single melt chamber of the furnace increases the output of the
furnace while retaining essentially the same footprint of space of
the furnace. The melt chamber of the furnace is mechanically
coupled to the loading chamber, with an isolation valve connecting
the two chambers. In some embodiments, the melt chamber and loading
chamber can be arranged vertically relative to each other, where an
elevator within the loading chamber can lift or otherwise move a
mold into a casting position below the melt boxes of the melt
chamber. In other embodiments, the melt chamber and loading chamber
can be arranged horizontally relative to each other, where a platen
can shift, slide, or otherwise move a mold into a casting position
below the melt boxes of the melt chamber. The throughput of the
furnace is increased in part because the duration of time required
to melt a charge of alloy is longer than the time required to load
an investment in a loading chamber of the furnace, and longer than
the time required to pour molten alloy into an investment.
Accordingly, the amount of molten alloy available to pour for a
given heating cycle is increased for any given casting, or in some
aspects, for multiple castings.
[0021] Superalloys are generally based on Group VIIIB elements and
usually consist of various combinations of iron (Fe), nickel (Ni),
cobalt (Co), and chromium (Cr), as well as lesser amounts of
tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb),
titanium (Ti), hafnium (Hf), or aluminum (Al). Additionally, other
elements can be used in superalloys as grain boundary components,
including boron (B), carbon (C), calcium (Ca), magnesium (Mg), and
zirconium (Zr). The three major classes of superalloys are nickel-,
iron-, and cobalt-based alloys. A furnace according to the present
disclosure can cast components made of metals, alloys, or
superalloys, where in some aspects the superalloys case can
include, but are not limited to: nickel-chromium alloys, iron-based
alloys, cobalt-based alloys, zirconium-doped alloys,
magnesium-doped alloys, and the like.
[0022] Molds used in conjunction with the vacuum induction melting
and casting system may have many different possible shapes
depending upon the articles desired to be cast. The mold may be
shaped for semi-continuous ingot production. In this case, the mold
may have an open top and bottom. Any number of molds may be moved
into and out of the casting position through a withdrawal port in a
sequential fashion. Alternatively, any suitable closed- or
open-bottom mold may be used. The mold may be shaped to create a
specific part or parts or any preformed shape which can be
converted into a part or parts. In such cases, the mold may have an
open top and closed bottom.
[0023] FIG. 1 is a flowchart illustrating a process for casting a
metal or alloy mold in combination with a dual melt box melt
chamber. The flowchart represents a portion of an investment
casting process, specifically a furnace casting cycle, during which
a ceramic mold is used to cast an alloy in a controlled atmospheric
environment, which in some aspects can be the casting of a
superalloy. A control system can be coupled with the furnace,
specifically in electronic communication with sensors (such as
temperature sensors) and actuating elements (such as chamber doors,
tilting assemblies, or elevators) located within the furnace. The
control system can include a non-transitory computer-readable
medium and microprocessors configured in part to receive and/or
process data from sensors located within the furnace. In some
aspects, the control system can further include a user interface to
allow for an operator to monitor and/or alter the function of the
furnace. In other aspects, the control systems can include
computer-executable instructions or algorithms to actuate
mechanical elements within the furnace to control a casting
process. The control unit can further be electronically coupled to
other, local or remote, non-transitory computer-readable mediums
(not shown) to transmit or receive data or operational
instructions.
[0024] In embodiments of the present disclosure, two ceramic
casting molds are used for each furnace casting cycle, and while
the two casting molds can be identical, for any given casting cycle
the casting molds are referred to as an initial casting mold and a
subsequent casting mold. At step 100, an initial casting mold is
pre-heated in a preheating oven external to a furnace loading
chamber. The initial casting mold can be formed by investment
casting or by other means known in the industry. The initial
casting mold can be pre-heated to a temperature of about
800.degree. C. to about 1,000.degree. C., preparing or heat-priming
the ceramic mold to receive molten alloy at temperatures at or
about 800.degree. C. to about 1,000.degree. C. or greater. In some
aspects, heat-priming a ceramic mold can increase the structural
quality of the casting ultimately formed from the molten alloy
poured into the mold, in part due to a reduction in any thermal
shock to the casting or formation effects potentially resulting
from a relatively steep temperature gradient at the interface
between the molten alloy and ceramic casting. At step 102, the
initial casting mold is transferred to and placed within a loading
chamber (also referred to as a mold chamber) of a furnace. At step
104, the pressure of the loading chamber is reduced from
atmospheric pressure, which can be accomplished by either or both
of a mechanical vacuum pump and a diffusion pump connected to the
loading chamber. In some aspects, the loading chamber can have its
internal pressure reduced to about one hundred millitorr (100
mTorr).
[0025] Concurrently, sequentially, or in parallel to loading a
pre-heated casting mold into the loading chamber of the furnace,
the melt chamber of the furnace can be prepared and an alloy can be
melted for casting. At step 106, charges of one or more alloys are
loaded into dual melt boxes of a melt chamber. The charges of
alloys can be of the same alloy, of similar alloys with different
ratios of component metals, or of different alloys. At step 108,
the pressure of the melt chamber is reduced from atmospheric
pressure, which can be accomplished by either or both of a
diffusion pump and a mechanical vacuum pump connected to the melt
chamber. In some aspects, the melt chamber can have its internal
pressure reduced to about five millitorr (5 mTorr). At steps 110
and 110', the temperature in the melt chamber is elevated such that
the charges of alloy in both the first melt box and the second melt
box within the melt chamber are rendered into molten alloy. The
melt chamber can be elevated to any given temperature necessary to
melt a given alloy. For example, to melt a charge of
nickel-chromium alloy such as Inconel 718, the melt chamber can be
elevated to a temperature of about 1,300.degree. C. or greater. For
many alloys, melting the charges of alloy in the melt chamber can
take from about five to ten minutes (5-10 min). The charges of
alloy are raised to a temperature above the melting temperature of
the alloy, but not above the boiling temperature of the alloy. (In
the industry, raising an alloy to such a temperature can be
referred to as "superheating"; this is not an accurate usage of
term according to the traditional physics definition of
superheating as related to boiling retardation or boiling
delay.)
[0026] Within the melt chamber, dual melt boxes can be arranged or
oriented on opposing sides of the location where a casing mold can
be positioned. In some aspects, each melt box can have an
independent tilt assembly, which can operate independently of each
other or in concert with each other. In other aspects, the melt
boxes can share a single tilt assembly that can incline each melt
box independently in an alternating or sequential order. The tilt
assembly or tilt assemblies for each of the melt boxes can be
positioned on the same side of the melt chamber, allowing for
access to the tilt assembly or tilt assemblies in melt chamber from
a single access point, and providing for efficient removal,
replacement, or maintenance of the tilt assembly or tilt
assemblies.
[0027] At step 112, an isolation valve (which in some aspects can
be a flapper valve) is opened thereby placing the loading chamber
and melt chamber in communication with each other. The pressure
between the loading chamber and melt chamber can balance to an
equilibrium. At step 114, the initial casting mold can be moved to
a casting position by a loading mechanism. In some aspects, the
melt chamber and loading chamber can be arranged vertically
relative to each other, where the movement of the initial casting
mold can be with an elevator mechanism, lifting the initial casting
mold up into the melt chamber to a casting position, from the
loading chamber. In other aspects, the melt chamber and loading
chamber can be arranged horizontally relative to each other, where
a platen mechanism can shift, slide, or otherwise move a mold into
a casting position below the melt boxes of the melt chamber. Both
the first melt box and the second melt box can be configured and
arranged to tilt and pour at the same casting position. At step
116, molten alloy from one of the first melt box or the second melt
box is poured into the initial casting mold. Each of the first melt
box and the second melt box has an individual tilting crucible to
accomplish the pouring action. In some aspects, the pouring of the
molten alloy at step 116 can take from about two to three seconds
(.about.2-3 sec). In further aspects, the amount of time required
to place a ceramic mold in the loading chamber (step 102), evacuate
the loading chamber atmosphere (step 104), open the isolation valve
(step 112), position the ceramic mold at the casting position (step
114), and pour the molten alloy into the ceramic mold (step 116)
can take about forty-five seconds (.about.45 sec).
[0028] At step 118, the initial casting mold, now holding the
casting of molten alloy, is withdrawn from the casting position and
withdrawn from the melt chamber. At step 120, the isolation valve
between the melt chamber and the loading chamber is closed. At step
122, the loading chamber is returned to atmospheric pressure, which
in some aspects can take about thirty seconds (30 sec). At step
124, the initial casting mold with the cast alloy is removed from
the loading chamber. The casting is allowed to cool and solidify at
atmospheric pressure. By allowing the casting to cool at
atmospheric pressure, the casting can have an equiaxed grain
structure, such that the grains of the metal can have an
approximately equal size and be randomly oriented in all directions
across and through the casting.
[0029] At decision step 126, a determination can be made if at
least one of the melt boxes in the melt chamber still holds a
charge of alloy, where the charge can be either in a molten or
solid state. In at least one of the melt boxes in the melt chamber
does still hold a charge of alloy, a second casting can be made
before reloading the melt boxes and proceeding though a further
melt chamber heating cycle. Accordingly, if at least one of the
melt boxes in the melt chamber still holds a charge of alloy, the
process returns to step 102, taking a subsequent pre-heated casting
mold for use in the process. (Alternatively, the process can return
to step 100 and pre-heat a new ceramic mold in the external
pre-heating oven.) The subsequent casting mold is placed in the
loading chamber at step 102, the loading chamber is again evacuated
with a vacuum system at step 104, and, if needed, the charge of
alloy remaining in the loading chamber is melted to a molten state.
The isolation valve between the loading chamber and the melt
chamber is again opened at step 112. The subsequent casting mold is
moved to a casting position at step 114. At step 116, the molten
alloy from whichever of the first melt box and the second melt box
still holds molten alloy is poured into the subsequent casting
mold.
[0030] At step 118, the subsequent casting mold, now holding the
casting of molten alloy, is withdrawn from the casting position and
withdrawn from the melt chamber. At step 120, the isolation valve
between the melt chamber and the loading chamber is closed. At step
122, the loading chamber is returned to atmospheric pressure. At
step 124, the subsequent casting mold with the cast alloy is
removed from the loading chamber, and the casting is allowed to
cool and solidify at atmospheric pressure.
[0031] In some implementations, during a casting cycle, after step
118 where a casting mold is withdrawn from the melt chamber, either
or both of the melt boxes can be reloaded (or "recharged") with an
alloy charge. Allowing the system to recharge the melt boxes in the
melt chamber as the casting within the loading chamber is returned
to atmospheric pressure and/or removed from the loading chamber can
further increase the efficiency and throughput of the overall
system.
[0032] The selection of which melt box to use at step 116 for an
initial casting mold can be based on a programmable selection
process, operator control, or the sensed or calculated temperature
at a region of the melt chamber. In some aspects, the melt box used
for the initial casting mold can alternate between furnace casting
cycles. In other aspects the same melt box can be used for each
initial casting mold for each furnace casting cycle.
[0033] At decision step 126, if neither of the melt boxes in the
melt chamber still holds a molten charge of alloy, the process
proceeds to step 128, ending the furnace casting cycle. Continuing
the production of castings with further furnace casting cycles
requires reloading the melt boxes with alloy charges, and requires
another duration of time to melt the alloy charges into molten form
for pouring into further ceramic molds.
[0034] FIG. 2 is a schematic diagram of a connected mold chamber
and melt chamber coupled with an atmospheric and vacuum control
system. A melt chamber 202 is coupled to a mold chamber 204 (i.e.
the loading chamber) via an isolation valve 206. The melt chamber
has a door through which alloy charges can be loaded into one or
more melt boxes within the melt chamber 202. Similarly, the mold
chamber 204 has a door through which ceramic casting molds can be
loaded. The melt chamber 202 is coupled to a first vacuum system
which can include a poppet valve structure 208 and a diffusion pump
210, which when active operates to reduce the pressure in the melt
chamber 202 below atmospheric pressure. The mold chamber 204 is
coupled to a first vacuum system 212, which can include a dry pump
and a blower, and when active operates to reduce the pressure in
the mold chamber 204 below atmospheric pressure.
[0035] The melt chamber 202 can be further coupled to a first
venting system 214, which can open and return the melt chamber 202
to atmosphere. Similarly, mold chamber 204 can be further coupled
to a second venting system 216, which can open and return the mold
chamber 204 to atmosphere. A holding pump 218 and a melt chamber
pumping package 220 can be further coupled to the poppet valve
structure 208 and diffusion pump 210. Either or both of the holding
pump 218 and melt chamber pumping package 220 are arranged as
backing, or upstream in series with, the diffusion pump 210.
Accordingly, when the diffusion pump 210 is in operation, either or
both of the holding pump 218 and melt chamber pumping package 220
can back-up, support, and/or maintain a desired pressure in the
melt chamber 202 and overall system. In particular, during a melt
cycle, the diffusion pump 210 is backed-up and/or supported by the
melt chamber pumping package 220.
[0036] A horizontal bar feeder 222 can deliver alloy charges into
the melt chamber 202, and in some embodiments more than one
horizontal bar feeder 222 can be coupled to the melt chamber 202. A
charge temperature sensor system 224 is coupled with the melt
chamber 202 and configured to measure the temperatures of the
molten charge in each melt box. A mold temperature sensor system
226 is coupled with the melt chamber 202 and configured to measure
the temperature of the mold cast within the melt chamber. Both of
the charge temperature sensor system 224 and mold temperature
sensor system 226 can be electronically coupled with a control
system to relay temperature data to an operator or processing
device.
[0037] A control system 228 can be located proximate or remote to
the overall mold chamber, melt chamber, and vacuum system
apparatus. The control system 228 can be electronically and
operationally coupled to the controllable systems of the apparatus,
and further provide a user interface for control by an operator. As
noted above, the control system 228 can include a non-transitory
computer-readable medium and microprocessors configured in part to
receive and/or process data from sensors located within the
furnace.
[0038] FIG. 3 is a schematic diagram of a furnace system 300 having
a connected melt chamber 302 and mold chamber 304. As illustrated,
the melt chamber 302 is positioned above the mold chamber 304.
Horizontal bar feeders 306, 306' can couple and feed into the melt
chamber 302, providing alloy charges to be loaded into the two melt
boxes 308, 308' within the melt chamber 302. In some aspects,
isolation valves melt boxes 307, 307' can be provided between the
horizontal bar feeders 306, 306' and the melt boxes 308, 308',
respectively. In many aspects, each of the melt boxes 308, 308'
have a tilting crucible aligned to pour molten alloy at a casting
position 316.
[0039] A withdrawal assembly 310 can be positioned below a casting
mold support 312, where the withdrawal assembly 310 is an elevator
that can move the casting mold support 312 up through an isolation
or flapper valve 314 into the melt chamber 302. The withdrawal
assembly 310 can position the casting mold support 312 at a casting
position 316 where both of the melt boxes 308, 308' can pour into
(at different times). Once a casting has been poured into a casting
mold located at the casting position 316, the withdrawal assembly
310 can retract from the melt chamber 302 and through the isolation
or flapper valve 314. The casting mold support 312 can be
positioned next to a mold cooling port 318 where a casting and
casting mold can be taken out of the mold chamber 304.
[0040] Additionally illustrated as offset in FIG. 3, the mold
chamber 304' is shown with the flapper valve 314' in positions at
and in between an open configuration and a closed configuration,
and further illustrates a maximum size of mold 313 that that the
mold chamber 304' and flapper valve 314' can accommodate. Further
illustrated as offset is a poppet valve and diffusion pump assembly
322 (otherwise located in a position occluded by the furnace system
300 in FIG. 3), which is coupled to and in communication with the
furnace system 300. As shown, the poppet valve and diffusion pump
assembly 322 is presented to show the relative size of the poppet
valve and diffusion pump assembly 322 as compared to the melt
chamber 302 and connected operational components.
[0041] In further embodiments, three melt boxes can be arranged
within a single melt chamber, further increasing the throughput of
casting of the furnace system. In yet further embodiments, four or
more melt boxes can be arranged within a single melt chamber,
further increasing the throughput of casting of the furnace
system.
[0042] As provided herein, the furnace system, including the
temperature and atmospheric controls for both the melt chamber and
the mold chamber can be electronically coupled with an
instrumentation interface with sensors and gauges to measure
sensory data in the furnace system. Such an instrumentation system
and interface can be electrically coupled to a microprocessor (or
other such non-transitory computer readable mediums) by wires or by
wireless means, and thereby send imaging data signals to the
microprocessor. The coupled microprocessor can collect sensory data
from the furnace and can further relay collected information to
other non-transitory computer readable mediums, and/or run
calculations on collected data and relay the calculated result to a
user-operable and/or user-readable display. The sensory data
captured by the furnace system can be evaluated according to
computer program instructions controlling the microprocessor
(either through hardware or software) to analyze or base
calculations on specific sensory data and in some aspects adjust
the temperature or pressure controls according to processing
parameters. In further aspects, an operator can monitor sensory
data and manually adjust temperature or pressure controls according
to processing parameters
[0043] The instrumentation which can include a microprocessor can
further be a component of a processing device that controls
operation of the instrumentation, in particular, the thermal or
pressure set points for melting and casting parameters of the
furnace. The processing device can be communicatively coupled to a
non-volatile memory device via a bus. The non-volatile memory
device may include any type of memory device that retains stored
information when powered off. Non-limiting examples of the memory
device include electrically erasable programmable read-only memory
("ROM"), flash memory, or any other type of non-volatile memory. In
some aspects, at least some of the memory device can include a
non-transitory medium or memory device from which the processing
device can read instructions. A non-transitory computer-readable
medium can include electronic, optical, magnetic, or other storage
devices capable of providing the processing device with
computer-readable instructions or other program code. Non-limiting
examples of a non-transitory computer-readable medium include (but
are not limited to) magnetic disk(s), memory chip(s), ROM,
random-access memory ("RAM"), an ASIC, a configured processor,
optical storage, and/or any other medium from which a computer
processor can read instructions. The instructions may include
processor-specific instructions generated by a compiler and/or an
interpreter from code written in any suitable computer-programming
language, including, for example, C, C++, C#, Java, Python, Perl,
JavaScript, etc.
[0044] The above description is illustrative and is not
restrictive, and as it will become apparent to those skilled in the
art upon review of the disclosure, that the present invention may
be embodied in other specific forms without departing from the
essential characteristics thereof. For example, any of the aspects
described above may be combined into one or several different
configurations, each having a subset of aspects. Further,
throughout the foregoing description, for the purposes of
explanation, numerous specific details were set forth in order to
provide a thorough understanding of the invention. It will be
apparent, however, to persons skilled in the art that these
embodiments may be practiced without some of these specific
details. These other embodiments are intended to be included within
the spirit and scope of the present invention. Accordingly, the
scope of the invention should, therefore, be determined not with
reference to the above description, but instead should be
determined with reference to the following and pending claims along
with their full scope of legal equivalents.
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