U.S. patent application number 15/660578 was filed with the patent office on 2018-02-01 for two stage melting and casting system and method.
The applicant listed for this patent is ARCONIC INC.. Invention is credited to Men Glenn Chu, Mark T. Kruzynski, Vivek M. Sample, Shawn P. Sullivan.
Application Number | 20180029110 15/660578 |
Document ID | / |
Family ID | 61011949 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180029110 |
Kind Code |
A1 |
Sample; Vivek M. ; et
al. |
February 1, 2018 |
TWO STAGE MELTING AND CASTING SYSTEM AND METHOD
Abstract
A system for two stage casting of a metal alloy is disclosed
that dispenses multiple feedstock metals into an arc melting
crucible via a pressurized inert gas or metal vapor chamber to
lower the volatilization rate of metals in an arc melting crucible
at a rate proportional to the composition of the final desired
alloy. The melt from the melting crucible enters a second stage
cold wall crucible through a passage, where the melt cools and
solidifies. A casting piston is used to slowly and progressively
withdraw the solidified alloy from the cold wall crucible as it
cools.
Inventors: |
Sample; Vivek M.;
(Murrysville, PA) ; Chu; Men Glenn; (Export,
PA) ; Kruzynski; Mark T.; (Export, PA) ;
Sullivan; Shawn P.; (Oakmont, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARCONIC INC. |
Pittsburgh |
PA |
US |
|
|
Family ID: |
61011949 |
Appl. No.: |
15/660578 |
Filed: |
July 26, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62368113 |
Jul 28, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 1/02 20130101; B22D
27/003 20130101; C22C 14/00 20130101; B22D 11/055 20130101; B22D
11/007 20130101; B22D 11/00 20130101 |
International
Class: |
B22D 11/00 20060101
B22D011/00; B22D 11/055 20060101 B22D011/055 |
Claims
1. A system for two stage casting of a metal alloy, comprising: a
first stage comprising a first crucible, a pressurized inert gas or
metal vapor chamber connected to the first crucible to adjust a
volatilization rate of feedstock metals in the first crucible such
that all metals introduced into the first crucible are retained in
a liquid state in the first crucible, and a feedstock control
system to dispense feedstock metals into the chamber and into the
first crucible, wherein the feedstock metals are dispensed at a
rate sufficient to achieve a target composition of a final metal
alloy; wherein at least one of the feedstock metals is in the form
of an electrode, wherein the system is operable to supply
electrical current to the electrode; and a second stage comprising
a second cooling crucible connected to the first crucible via a
passageway.
2. The system according to claim 1 further comprising a layer of
metal salt/slag on the first crucible, the layer of metal salt/slag
having an upper surface.
3. The system according to claim 2 wherein the electrode has a tip
submerged below the upper surface of the layer of metal
salt/slag.
4. The system according to claim 3 further comprising one or more
secondary feedstock elements fed into the metal salt/slag via a
feedstock control system.
5. A two stage method of producing a metal alloy comprising;
placing a metal salt layer in a first crucible, wherein the first
crucible is connected to a second crucible via a passageway;
introducing a first electrode into the metal salt layer; passing an
electrical current through the first electrode to produce a slag
layer in the first crucible from the metal salt layer via
resistance heating; pushing the electrode into the slag layer so
that a tip of the electrode begins to melt into a molten
composition below the slag layer in the first crucible; introducing
secondary feedstock elements into the slag layer to melt the
secondary feedstock elements into the molten composition in the
first crucible; continuing to melt the electrode and the secondary
feedstock elements into the composition until a desired volume of
composition is reached; once the desired volume of molten
composition is achieved, opening the passageway to the second
crucible such that the molten composition flows into the second
crucible; and cooling the composition in the second crucible to a
solid state.
6. The method of claim 5 wherein cooling the composition comprises
progressively lowering a piston attached to a bottom of the second
crucible as the molten composition solidifies bottom up in the
second crucible.
7. The method of claim 5 wherein the electrode is a metal having a
highest melting point of any of the elements to be introduced into
the first crucible.
8. The method of claim 5 wherein the electrode is a hollow
tube.
9. The method of claim 5 wherein the electrode is titanium or a
titanium alloy.
10. The method of claim 5 wherein the resistive heating of the
metal salt by the first electrode heats the slag layer to a
temperature above a secondary element melting point.
11. The method of claim 5 wherein as a bottom portion of the
composition in the secondary crucible solidifies the secondary
crucible is withdrawn such that the bottom portion is progressively
lowered relative to a top of the secondary crucible.
12. A system for two stage casting of a metal alloy, comprising: a
first stage comprising a first crucible, a pressurized inert gas or
metal vapor chamber connected to the first crucible to adjust a
volatilization rate of feedstock metals in the first crucible such
that all metals introduced into the first crucible are retained in
a liquid state in the first crucible, and a feedstock control
system to dispense feedstock metals through the chamber and into
the first crucible, wherein the feedstock metals are dispensed at a
rate sufficient to achieve a molten composition of a final metal
alloy; wherein at least one of the feedstock metals is in the form
of an electrode, wherein the system is operable to supply
electrical current to the electrode; an electromagnetic stirring
mechanism operable to stir the molten composition in the first
crucible; and a second stage comprising a second cooling crucible
connected to the first crucible via a passageway.
13. The system according to claim 12 further comprising a layer of
metal salt/slag on the first crucible, the layer of metal salt/slag
having an upper surface.
14. The system according to claim 13 wherein the electrode has a
tip submerged below the upper surface of the layer of metal
salt/slag.
15. The system according to claim 14 further comprising one or more
secondary feedstock elements fed into the metal salt/slag via a
feedstock control system.
16. The system according to claim 15 wherein the secondary
feedstock elements are high density materials that sit below the
upper surface of the slag layer.
17. The system according to claim 15 wherein one of the electrode
and the secondary elements include one or more hollow elements
extending below the upper surface of the slag layer.
18. The system according to claim 13 wherein the slag layer is a
metal salt/slag layer having an increasing temperature gradient
from the upper surface to a bottom of the layer.
19. The system according to claim 15 wherein the secondary elements
extend below the upper surface of the slag layer.
20. The system according to claim 15 wherein the layer has a
thickness sufficient to achieve a first temperature associated with
its upper surface, and a second temperature associated with its
lower surface, wherein the first temperature is lower than the
melting point of the electrode and wherein the second temperature
is higher than the melting point of the electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of priority of U.S.
Provisional Patent Application No. 62/368,113, filed Jul. 28, 2016,
entitled "TWO STAGE MELTING AND CASTING SYSTEM AND METHOD", which
is incorporated herein by reference in its entirety.
SUMMARY OF THE DISCLOSURE
[0002] A "metal alloy" as used herein is defined as an alloy based
on a metal. One species is a multi-component alloy wherein the
multi-component alloy realizes an entropy of mixing of at least
1.25. Species within the genus of "metal alloy" includes aluminum
alloys, nickel alloys, titanium alloys, steels, cobalt alloys, and
chromium alloys.
[0003] As used herein, "multi-component alloy product" and the like
means a product with a metal matrix, where a plurality of elements,
typically four or more different elements make up the matrix, and
where the multi-component product comprises 5-35 at. % of the four
or more elements. In one embodiment, at least five different
elements make up the matrix, and the multi-component product
comprises 5-35 at. % of the at least five elements. In one
embodiment, at least six different elements make up the matrix, and
the multi-component product comprises 5-35 at. % of the at least
six elements. In one embodiment, at least seven different elements
make up the matrix, and the multi-component product comprises 5-35
at. % of the at least seven elements. In one embodiment, at least
eight different elements make up the matrix, and the
multi-component product comprises 5-35 at. % of the at least eight
elements. As described below, additives may also be used relative
to the matrix of the multi-component alloy product to achieve an
alloy generated by the system.
[0004] This disclosure presents a system for two stage casting of
any metal alloy product such as a multi-component alloy. The first
stage involves melting multiple feedstock of elements or known
alloys and generating a desired composition of matter by varying
the speed of the feedstock advancement into a molten form in a high
pressure inert gas or metal vapor environment such that all metals
introduced into the first crucible are retained in a liquid state
in the first crucible. The second stage involves casting the
desired composition by pulling the liquid phase crucible contents
from the first stage into a second cooling crucible through a
passageway using a casting piston attached to the cooling crucible
and permitting the composition to cool into a solid state as the
piston slowly withdraws the cooling crucible.
[0005] Briefly, a metal alloy with a specific composition is
selected to be casted. The elemental components for this metal
alloy are prepared as feedstock for the two stage casting system
and loaded via a high pressure vacuum chamber into a melting
crucible that has a surface layer several inches thick of a metal
salt. This metal salt typically comprises CaF.sub.2 along with
minor additives and is heated via resistive heating current
supplied by an electrical circuit. The first melting crucible is
electrically connected to an electrical current power supply. The
primary element feedstock acts as an electrode in the electrical
circuit. Electrical current through the primary electrode, through
the slag to the surface of the first crucible causes the metal salt
layer to heat up, generating a high temperature slag layer, which
in turn causes the primary feedstock electrode and secondary
feedstock elements immersed in the slag to melt and puddle in the
first melting crucible.
[0006] Preferably the primary element feedstock electrode and
secondary feedstocks are dispensed through a vacuum pressure
chamber on top of the metal salt/slag layer on the melting
crucible. This chamber is pressurized with inert gas or metal vapor
and maintained at a temperature and pressure suitable to stop
element evaporation during the melting process, since various
metals melt at different pressures and temperatures. Once all of
the feedstock elements have reached liquid phase in the crucible,
the melted feedstock is stirred, preferably by inductive or
electromagnetic stirring, to ensure consistent uniform distribution
of each element or constituent of the melt. After being stirred to
a homogenous state, the mixture is withdrawn through an extraction
valve, passage or port into a second stage cooling crucible beneath
the first or melting crucible using negative pressure from a
casting piston. In the second stage crucible, preferably a cold
wall crucible, the mixture is cooled and forms a quiescent metal
head on the casting piston. The casting piston is then slowly
withdrawn as the melt solidifies and the cooled and solidified
metal alloy can then be removed for further treatment or
modification.
[0007] A system for two stage casting of a metal alloy in
accordance with the present disclosure preferably has in a first
stage a first melting crucible, a pressurized inert gas or metal
vapor chamber connected to the first crucible to adjust a
volatilization rate of metals in the melting crucible such that all
metals introduced into the first crucible are retained in a liquid
state in the first crucible, and a feedstock control system to
dispense multiple feedstock metals into the chamber and into the
melting crucible. The feedstock metals are dispensed at a rate
sufficient to achieve a target composition of a final metal alloy.
At least one of the multiple metal feedstock metals is in the form
of an electrode, part of an electrical power supply supplying
electrical current to the electrode.
[0008] The second stage includes a second cooling crucible
connected to the first melting crucible via a passageway. The
system preferably includes a layer of metal salt/slag disposed on
an upper surface of the melting crucible. A distal tip of the
electrode is submerged below the upper surface of the metal
salt/slag layer. Electrical current through the electrode passes
through the upper surface layer of the metal salt/slag and
resistively heats the slag layer to a temperature above the melting
point of the electrode. Secondary feedstock elements are also
positioned in the high pressure vacuum chamber so as to extend into
the metal salt/slag layer. Some of the secondary feedstock elements
may be high density materials. Other of the secondary feedstock
elements may be hollow so as to carry low density materials into
the slag layer and into the first melting crucible.
[0009] The slag layer preferably has an increasing temperature
gradient from the upper surface of the layer to a bottom of the
layer, and is preferably controlled such that the upper surface has
a temperature below the melting point of the primary or secondary
elements. The bottom surface of the slag layer preferably has a
temperature greater than the melting temperature of the element
having the highest melting temperature. Preferably the slag layer
has a thickness sufficient to achieve a first temperature
associated with its upper surface, and a second temperature
associated with its lower surface, wherein the first temperature is
lower than the melting point of the electrode and wherein the
second temperature is higher than the melting point of the
electrode.
[0010] A two stage method of producing a metal alloy in accordance
with the present disclosure comprises placing a metal salt layer in
a first crucible, wherein the first crucible is connected to a
second crucible via a passageway, introducing a first electrode
into the metal salt layer, passing an electrical current through
the first electrode to produce a slag layer in the first crucible
from the metal salt layer via resistance heating, pushing the
electrode into the slag layer so that a tip of the electrode begins
to melt into a molten composition below the slag layer in the first
crucible, introducing secondary feedstock elements into the heated
slag layer to melt the secondary feedstock elements into the molten
composition in the first crucible and continuing to melt the
electrode and the secondary feedstock elements into the composition
until a desired volume of composition is reached. Once the desired
volume of molten composition is achieved, the method comprises
opening the passageway to the second crucible such that the molten
composition flows into the second crucible; and cooling the
composition in the second crucible to a solid state.
[0011] The method may further include progressively lowering a
piston attached to a bottom of the second crucible as the molten
composition solidifies bottom up in the second crucible. Preferably
during the first stage the primary electrode is a metal having a
highest melting point of any of the elements to be introduced into
the first crucible. In one embodiment the electrode is a hollow
tube. The electrode may be titanium or a titanium alloy. In an
embodiment the resistive heating of the metal salt by the first
electrode heats the slag layer to a temperature above a secondary
element melting point. In one embodiment, as a bottom portion of
the composition in the secondary crucible solidifies the secondary
crucible is withdrawn via a piston such that the bottom portion is
progressively lowered relative to a top of the secondary crucible,
and this progressive lowering is preferably continued until a solid
ingot of the composition can be withdrawn for removal from the
secondary crucible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic cross-sectional diagram of an
exemplary embodiment of a two stage multi-component alloy casting
system in accordance with the present disclosure.
[0013] FIG. 2 is a schematic cross-sectional diagram of the upper
portion of the embodiment shown in FIG. 1 illustrating one
embodiment of an electrical power supply circuit.
[0014] FIG. 3 is a schematic cross-sectional diagram of an upper
portion of the embodiment shown in FIG. 1 illustrating an exemplary
electromagnetic stirring arrangement.
[0015] FIG. 4 is a schematic cross-sectional diagram of the
crucible passageway shown in FIG. 1 illustrating an exemplary
passageway closure.
DETAILED DESCRIPTION
[0016] In the description that follows, like numerals are utilized
to describe like components and subcomponents in the various
views.
[0017] As noted above, this disclosure presents a system/apparatus
for two stage casting of a metal alloy such as a multi-component
alloy. The system includes a first melting crucible 6 and a second
cooling crucible 8 connected to the first crucible 6 via a
selectively closable passageway 7. The upper surface of the first
crucible 6 is layered with a metal salt that when resistively
heated forms a relatively thick slag layer 20 on the upper surface
of the first crucible 6 and the melt 11 formed thereon.
[0018] This slag layer 20 may be 4 to 6 or more inches thick. It
must be thick enough to have a large temperature gradient from top
to bottom such that the upper slag layer surface temperature is
lower than the lowest melting point of the feedstock element. The
bottom surface of the slag layer 20 preferably has a temperature
higher than the melting point of any of the feedstock elements.
[0019] The feedstock elements 1, 2, 3 to produce the desired alloy
composition shown as melt 11 include at least one feedstock element
that acts as a first electrode 1 connected to a remote electrical
power supply 21 via a feedstock controller 4. Secondary solid
elements 2, 3 are also included, whose feed rate is also controlled
by the feedstock controller 4, that add secondary elements to
achieve the desired end composition of melt 11. These elements 1,
2, 3 may be solid, for high density materials. The distal ends of
these solid elements will sit below at least the surface of the
slag layer 20. Hollow elements that act as a tube to feed high
volatile/low density materials to below the surface of the slag
layer 20 may also be utilized.
[0020] FIG. 1 shows basic diagram of a two stage metal alloy
casting system 100 in accordance with one embodiment of the present
disclosure. The system 100 allows feedstocks 1, 2 and 3 to be fed
from a feedstock controller 4 into a melting first crucible 6. The
exemplary feedstock elements 1, 2, and 3 are each comprised of
elemental metals or pre-alloys which can be melted together to form
a desired molten multi-component alloy 11. The feedstocks 1, 2, and
3 and crucible 6 are disposed within a pressurized gas chamber 5
that may be under a vacuum or pressurized with an inert gas (He,
Ar, N) or metal vapor, in some embodiments, to lower the
volatilization rate of the various metal feedstocks. Many metal
elements utilized in alloying processes volatize or melt at
different temperatures and pressures. Preferably the chamber 5 is
maintained at a desired temperature and pressure to maintain all
constituent elements in a liquid state during processing as
described herein. Use of a pressure chamber 5 results in an as cast
microstructure of the melt as well as the end product solidified
alloy 9 that includes volatile ingredient elements such as Li, Mg,
and Zn in mixture with Titanium that would otherwise have been
vaporized if pressure chamber 5 were not utilized.
[0021] The feedstock motion and power controller 4 is electrically
powered via a DC power supply 21 shown in FIG. 2. DC power is
supplied to the system 100 via the power supply 21 such that
current is fed through a primary feedstock electrode element 1. The
feedstock controller 4 is given feed rate instructions based on the
specific amounts of each feedstock 1, 2, or 3 needed to produce the
desired multi-component alloy product. The primary feedstock
element electrode 1 is fed through the vacuum chamber 5 into the
melting first crucible 6 which has a surface layer typically
several inches thick of slag 20. This slag layer 20 typically
comprises CaF.sub.2 along with minor additives and is heated via
the arc melting electrical circuit shown in FIG. 2. The primary
element feedstock 1 acts as an electrode in the melting electrical
current circuit shown in FIG. 2. The melting first crucible 6 is
electrically connected to the power supply 21, as a return, thus
completing the electrical circuit. The slag 20 acts as a series
resistive element in this electrical circuit of the power supply
21. The current passing through the electrode 1 resistively heats
the slag 20 and melts the tip of the primary electrode 1 into the
first crucible 6 initially forming a melt 11. Electrical current
fed through the feedstock controller 4 via the primary electrode 1,
and through the slag 20 to the first crucible 6 via resistive
heating causes the slag 20 to heat up, which in turn causes the
primary feedstock electrode 1 and then the secondary feedstock
elements 2 and 3, also immersed in the heated slag 20, to melt and
puddle as a common melt 11 in the melting first crucible 6.
[0022] The feedstock controller 4 regulates the feed rate of each
of the feedstocks 1, 2 and 3 into the crucible 6 in proportion to
the desired composition melt 11 to be generated. Furthermore, the
feedstock controller 4 adjusts the position of the primary
electrode 1 tip in the slag 20 so as to promote melting at a
controlled rate.
[0023] The composition melt 11 is preferably stirred in the first
crucible 6. Stirring of the melt 11 may be accomplished by
induction or electromagnetic stirring, mechanical stirring, sonic
or ultrasonic agitation, or other mechanism. One exemplary
arrangement for electromagnetic stirring is illustrated in FIG. 3.
Multi-component alloy melts 11 may contain elements which have a
significant difference in density. Since the properties of a
multi-component alloy depend on the uniformity of the elemental
composition throughout the material, it is necessary to stir the
liquid phase metal components together to ensure uniformity before
they solidify. The composition 11 may be stirred
electromagnetically by providing AC power to at least one induction
coil 13 using a magnetic stirring control system 12.
[0024] FIG. 3 shows an electromagnetic stirring control 12. The
magnetic stirring control 12 allows the system 100 to dynamically
modify the parameters which control the magnetic stirring of liquid
phase metals 11 in the first crucible 6. The magnetic stirring
control 12 is a component capable of adjusting the power to a
magnetic stirring mechanism, such as a series of coils 13, in order
to vary the magnetic field allowing magnetic stirring of materials
with different densities. An AC power source 14 supplies the
magnetic stirring controller 12. The magnetic stirring controller
12 adjusts the power and phasing to the magnetic stirring induction
coils 13, in order to vary the magnetic field allowing magnetic
stirring of materials with different densities.
[0025] Once the melt 11 is adequately stirred to form the desired
consistency of the multi-component alloy product, the melt 11 is
transported through an extraction valve, passageway, or port 7 into
a second chamber including a cold wall cooling crucible 8. The cold
wall crucible 8 is cooled so that a quiescent metal alloy
composition head 9 comprising a solid metal alloy composition may
form in the cold wall crucible 8 on the casting piston 10. The
casting piston 10 may then be lowered or withdrawn and the solid
metal head 9 removed from the top of the piston 10 for further use
or treatment as may be desired.
[0026] The feedstocks 1, 2, 3 described herein include at least two
separate sources of raw material for the multi-component alloy
product, and may include any form of elemental metals (e.g. Li, Ti,
Mn, Cr, Fe, Co, Ni, Cu, Ag, W, Mo, Nb, Al, Cd, Sn, Pb, Bi, Zn, Ge,
Si, Sb, and Mg) or pre-alloys, which can be in cylindrical wire
form, granulated pellets, or powdered, for example. Preferably the
primary element electrode 1 is the highest melting temperature
element or alloy, such as Titanium. This way, as current is fed
through the electrode 1 into the slag 20, it will be heated high
enough to progressively melt the Titanium. The heated slag 20 will
in turn heat and melt the secondary feedstocks 2 and 3 such that
they melt through the slag 20 into the first crucible 6 to coalesce
into the melt 11.
[0027] Optionally, the first crucible 6 may be constructed of a
consumable metal material itself such that a portion of the first
crucible 6 melts into and forms part of the melt 11 in the first
stage. Also, one of the feedstock elements may be a pre-alloy such
as an Aluminum and/or Titanium alloy or one or more of the
feedstock elements 1, 2, 3 may be a more complex multi-component
alloy such as one that comprises at least three or four or more
element metals pre-alloyed together in a prior two stage process as
above described.
[0028] In the embodiments described herein, the feedstock elements
and alloys may be in a cylindrical wire form, granulated pellets,
or powdered, etc. The electrode 1 may be a solid rod or may be
hollow, or a hollow tube filled with another component element or
alloy to become a part of the melt 11. Furthermore, the slag 20 may
also contain one or more feedstock elements or additives within it
that combine with the feedstock elements 1, 2, and 3 during
formation of the melt 11.
[0029] FIG. 4 shows one exemplary embodiment of the system 100 in
which a cooled valve pin 30 is utilized to controllably open a
conical entrance portion 29 of the passageway 7 out of the crucible
6 into the solidifying head 9 on top of the cold crucible 8. The
entrance 29 to the passageway 7 is closed during the melting and
formation of the melt 11 as above described. At least the entrance
29 of the passageway 7 is closed by a hollow trapezoidal tip shaped
valve disk pin 30 during those operations. The passageway 7 is
shown in FIG. 4 exaggerated in size for explanation purposes. The
passageway 7 may be essentially eliminated downstream of entrance
29 such that the entrance 29 is all that exists of passageway 7
into the second cooling crucible 8. When it is desired to transfer
the melt 11 into the crucible 8, the valve pin 30 is slowly
withdrawn while a cooling liquid 31 is circulated within the valve
pin 30. Raising the pin 30 opens a gap A which is carefully
controlled such that the melt 11 passing by the tip of the pin 30
and through the passageway 7 via gap A does not change to a solid
state prior to dropping onto the head 9. This may be controlled by
reducing or increasing the gap A and by regulating the temperature
of the cooling fluid 31 within the pin 30 during the transfer
operation. The first crucible 6, if made of a conductive metal such
as copper, may also be cooled or thermally regulated such that the
melt 11 formed via resistive heating of the slag layer 20 remains
liquid during the first stage formation of melt 11 described above
and during the transfer process through passageway 7.
[0030] While various embodiments of the new technology described
herein have been described in detail, it is apparent that
modifications and adaptations of those embodiments will occur to
those skilled in the art. For example, the two stage process and
apparatus may be utilized over and over again utilizing one or more
intermediate solid multi-component alloys produced in a previous
stage as a pre-alloy element 1, 2 or 3 in a subsequent use of the
system 100. It is to be expressly understood that such
modifications and adaptations are within the spirit and scope of
the presently disclosed technology.
* * * * *