U.S. patent application number 10/146461 was filed with the patent office on 2003-11-20 for melting crucible and method.
Invention is credited to Andruchowitz, Jason S., Astrab, John M., Bayles, Robert H., Bornemann, Edward W., Maslen, James D., Miller, Evan R., Normann, George J., Osagie-Erese, Albert, Tarby, Mark K., Todaro, Thomas J..
Application Number | 20030213575 10/146461 |
Document ID | / |
Family ID | 29400470 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030213575 |
Kind Code |
A1 |
Todaro, Thomas J. ; et
al. |
November 20, 2003 |
Melting crucible and method
Abstract
A melting method and a melting crucible assembly involve
positioning a disposable (non-reusable), self-supporting refractory
liner body in a refractory host crucible and melting a metallic
charge in the liner residing in the host crucible. The melted
metallic charge is poured from the refractory liner body, and the
used refractory liner body is removed from the host crucible for
discarding and replaced with a clean, new (unused) refractory liner
body in the host crucible for melting the next metallic charge
therein.
Inventors: |
Todaro, Thomas J.; (Wharton,
NJ) ; Tarby, Mark K.; (Colonia, NJ) ;
Andruchowitz, Jason S.; (Old Bridge, NJ) ; Astrab,
John M.; (Belvidere, NJ) ; Bayles, Robert H.;
(Hackettstown, NJ) ; Bornemann, Edward W.;
(Rockaway, NJ) ; Maslen, James D.; (Landing,
NJ) ; Miller, Evan R.; (Sparta, NJ) ; Normann,
George J.; (East Stroudsburg, PA) ; Osagie-Erese,
Albert; (East Orange, NJ) |
Correspondence
Address: |
Mr. Edward J. Timmer
Walnut Woods Centre
5955 W. Main Street
Kalamazoo
MI
49009
US
|
Family ID: |
29400470 |
Appl. No.: |
10/146461 |
Filed: |
May 14, 2002 |
Current U.S.
Class: |
164/135 ;
164/335 |
Current CPC
Class: |
C21C 5/5241 20130101;
F27B 14/061 20130101; H05B 6/26 20130101; F27D 3/15 20130101; F27D
3/14 20130101; F27D 1/0006 20130101; Y02P 10/253 20151101; F27B
14/04 20130101; Y02P 10/25 20151101; F27B 14/10 20130101; C22B
9/003 20130101 |
Class at
Publication: |
164/135 ;
164/335 |
International
Class: |
B22D 041/02; B22D
041/05 |
Claims
We claim
1. A method of melting and pouring successive metallic charges,
comprising positioning a metallic charge in a disposable,
self-supporting refractory vessel, melting the metallic charge in
said vessel under vacuum or a protective atmosphere, pouring the
melted metallic charge from said vessel, discarding said vessel,
and melting a next metallic charge in a clean, new refractory
vessel under a vacuum or protective atmosphere.
2. The method of claim 1 wherein the metallic charge comprising a
nickel base superalloy or a cobalt base superalloy is melted in a
melting chamber section in said liner body.
3. The method of claim 2 wherein the melted metallic charge is
poured from a pouring chamber section communicated to said melting
chamber section in said liner body at a location below a melt level
of the melted metallic charge in said liner body.
4. The method of claim 1 wherein said metallic charge is melted by
energizing an induction coil disposed about said vessel.
5. The method of claim 1 wherein the melted metallic charge is
melted under a protective atmosphere selected from inert gas or
nitrogen.
7. A method of melting and pouring a metallic charge, comprising
positioning a metallic charge in a disposable refractory liner body
residing in a refractory host crucible, melting the metallic charge
in said liner body, pouring the melted metallic charge from said
liner body, removing said liner body from said host crucible, and
placing a clean, new refractory liner body to melt the next
metallic charge.
7. The method of claim 6 wherein the metallic charge comprising a
nickel base superalloy or cobalt base superalloy is melted in a
melting chamber section in said liner body.
8. The method of claim 7 wherein the melted metallic charge is
poured from a pouring chamber section communicated to said melting
chamber section in said liner body at a location below a level of
the melted metallic charge in said liner body.
9. The method of claim 6 wherein said metallic charge is melted by
energizing an induction coil disposed about the host crucible.
10. The method of claim 6 wherein the melted metallic charge is
poured into a mold.
11. A melting crucible assembly comprising a refractory host
crucible, and a disposable, self-supporting refractory liner body
disposed in the host crucible and in which a metallic charge is
melted, said liner body including a partition wall that forms a
melting chamber section and a pouring chamber section communicated
to one another at a location disposed below a melt level of a
melted metallic charge in said liner body such that melted metallic
charge below said level flows from the melting chamber section to
the pouring chamber section when said crucible assembly is
tilted.
7. The assembly of claim 6 including an induction coil about the
host crucible.
8. The assembly of claim 6 wherein said host crucible resides in a
bed of refractory grog particulates.
9. The assembly of claim 6 wherein said liner body is received in
said host crucible with clearance that allows said liner body to be
removed from said host crucible after said metallic charge has been
melted and poured.
10. The assembly of claim 6 wherein said liner body has a
cylindrical tubular shape.
11. The assembly of claim 10 wherein said liner body has an outer
diameter that is less than an inner diameter of a cylindrical side
wall of said host crucible.
12. The assembly of claim 6 wherein said partition wall extends
downwardly in said liner body when it is oriented in an upstanding
position.
13. The assembly of claim 12 wherein said partition wall terminates
at its lowermost end a distance above a bottom wall of said liner
body such that a passage is formed between said melting chamber
section and said pouring chamber section for flow of clean melted
metallic material from said melting chamber section to said pouring
chamber section.
14. The assembly of claim 6 wherein said partition wall is
configured to form a recess along a side thereof facing said
melting chamber section.
15. The assembly of claim 14 wherein said recess is adapted to
receive and position a cylindrical ingot or billet of said metallic
charge material.
16. The assembly of claim 6 wherein said liner body includes a
cover that is connected to the uppermost end of said partition
wall, said cover including an opening through which melted metallic
charge in said pouring chamber section is poured when said crucible
assembly is tilted.
17. The combination of a melting vessel in a chamber having a
vacuum or a protective atmosphere therein, comprising a disposable,
self-supporting refractory vessel in which a metallic charge
comprising a nickel base superalloy or cobalt base superalloy is
melted, said vessel including a partition wall that forms a melting
chamber section and a pouring chamber section communicated to one
another at a location disposed below a melt level of melted
metallic charge in said vessel such that melted metallic charge
below said level flows from the melting chamber section to the
pouring chamber section when said vessel is tilted.
18. The combination of claim 17 wherein said vessel is received in
said host crucible with clearance that allows said vessel to be
removed from said host crucible after said metallic charge has been
melted and poured.
19. The combination of claim 17 wherein said partition wall extends
downwardly in said liner body when it is oriented in an upstanding
position.
20. The combination of claim 19 wherein said partition wall
terminates at its lowermost end a distance above a bottom wall of
said liner body such that a passage is formed between said melting
chamber section and said pouring chamber section for flow of clean
melted metallic material from said melting chamber section to said
pouring chamber section.
21. The combination of claim 17 wherein said partition wall is
configured to form a recess along a side thereof facing said
melting chamber section, said recess being adapted to receive and
position a cylindrical ingot or billet of said metallic charge
material.
22. The combination of claim 17 wherein said vessel includes a
cover that is connected to the uppermost end of said partition
wall, said cover including an opening through which melted metallic
charge in said pouring chamber section is poured when said crucible
assembly is tilted.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to melting of a metal or alloy
in a crucible and to a crucible assembly for such melting.
BACKGROUND OF THE INVENTION
[0002] Induction melting crucibles are known in the metal casting
art for melting a charge of metal or alloy. An induction melting
crucible typically includes a ceramic crucible around which an
induction coil is disposed to heat and melt a solid metal or alloy
charge. A refractory material is packed on the inside of the
induction coil to form a recess for receiving the crucible. The
crucible may be mounted on trunnions and tilted about the trunnion
axis to pour a molten metal charge over a lip of the crucible into
an underlying mold or other molten metal receiving vessel.
Alternatively, the crucible may include a discharge opening in the
bottom wall thereof and a stopper rod, plug or other closure
mechanism to prevent release of the molten metal from the crucible
through the discharge opening to an underlying mold or other molten
metal receiving vessel until the molten metal or alloy is at a
proper casting temperature.
[0003] In the vacuum induction melting of oxygen-reactive nickel
base superalloys and cobalt base superalloys used to investment
cast gas turbine engine components, such as turbine blades, vanes
and other components, the melt of superalloy contained in the
crucible can include dross and other contaminants floating on the
melt surface. Dross typically comprises metal oxides that migrate
to and float on the melt surface. Other contaminants on or in the
melted charge can include non-metallic inclusions, such as metal
nitrides, sulfides and the like and unreacted crucible particulate
material. It is desirable to reduce the amount of dross and other
contaminants floating on the melt surface that are poured from the
crucible into the investment mold where they ultimately may
adversely affect the quality of the superalloy casting produced in
the investment mold.
SUMMARY OF THE INVENTION
[0004] The present invention provides in one embodiment a method of
melting and pouring successive metallic charges, such as for
example oxygen-reactive nickel base superalloys or cobalt base
superalloys, comprising positioning a metallic charge in a
disposable, self-supporting refractory vessel, melting the metallic
charge in the vessel under vacuum or a protective atmosphere such
as for example an inert gas, nitrogen, etc., pouring the melted
metallic charge from the vessel, discarding the vessel, and melting
the next metallic charge in a clean, new refractory vessel.
[0005] The present invention provides in another embodiment a
melting method and a melting crucible assembly that involve
positioning a disposable (non-reusable), self-supporting refractory
liner body in a refractory host crucible and melting a metallic
charge such as, for example, a solid nickel or cobalt base
superalloy charge in the liner residing in the host crucible. The
melted metallic charge is poured from the refractory liner body
into a mold, and the used (spent) refractory liner body is removed
from the host crucible for discarding and replaced with a clean,
new (unused) refractory liner body in the host crucible for melting
the next metallic charge therein.
[0006] In a particular embodiment of the invention, the disposable
refractory liner body comprises a tubular body having a closed
bottom wall to form an internal chamber. A partition wall is
present in the internal chamber of the liner body to provide a
melting chamber section and a pouring chamber section communicated
to one another at a location disposed below an existing level of
melted metallic charge (melt level) in the liner body. A pour
opening is disposed in a cover that partially overlies the pouring
chamber section and is connected to the uppermost end of the
partition wall. The partition wall is configured such that clean
melted metallic charge below the existing melt level flows to the
pouring chamber section when the crucible assembly is tilted, while
dross and other contaminants floating on the melt surface in the
melting chamber section remain confined in that chamber section.
Use of a clean, new refractory liner body for melting each
respective metallic charge and the flow of the melted metallic
charge from the melting chamber section to the pouring chamber
section reduces the amount of dross and other contaminants that
will be poured from the pouring chamber section into a mold.
[0007] The above and other objects and advantages of the present
invention will become more readily apparent from the following
drawings taken in conjunction with the following detailed
description.
DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional view of a melting crucible assembly,
with the liner body shown in elevation, taken along lines 1-1 of
FIG. 2 in accordance with an illustrative embodiment of the
invention.
[0009] FIG. 2 is a plan view of a melting crucible assembly in
accordance with an illustrative embodiment of the invention. The
support tray for the melting crucible assembly is omitted for
convenience.
[0010] FIG. 3 is a plan view of the refractory liner body.
[0011] FIG. 4 is a sectional view taken along lines 4-4 of FIG. 3
of the refractory liner body.
[0012] FIG. 5 is an isometric view of the refractory liner
body.
[0013] FIG. 6 is a sectional view of the crucible assembly with a
solid ingot shown in elevation received in a recess on the
partition wall of the refractory liner body tilted to a near
horizontal position.
[0014] FIG. 7 is a view showing melted metallic material being
poured from the liner body into a mold.
[0015] FIG. 8 is a longitudinal sectional view of a melting vessel
in accordance with another illustrative embodiment of the
invention.
DESCRIPTION OF THE INVENTION
[0016] FIGS. 1-7 illustrate schematically a melting crucible
assembly 10 for melting a solid metallic charge, such as a metal or
alloy. The solid metallic charge can be in the form an ingot,
billet, sponge, particulates, and other available material forms.
For purposes of illustration and not limitation, the melting
crucible assembly 10 is especially useful and beneficial to heat
and melt a solid metallic charge (e.g. an ingot or billet)
comprising an oxygen-reactive nickel base superalloy or cobalt base
superalloy in chamber C. Nickel base superalloys and cobalt base
superalloys are well known and widely used in making investment
cast gas turbine engine components having an equiaxed grain
microstructure or a directionally solidified microstructure that
includes a columnar grain microstructure or single crystal. Such
superalloys are described herein as oxygen-reactive in the sense
that the superalloys usually include alloying elements that are
prone to react with or have a high affinity for oxygen at melting
temperatures employed. For purposes of illustration and not
limitation, nickel base and cobalt base superalloys include, but
are not limited to, CMSX-3, CMSX-4, INCONEL 625, STELLITE 25, and
STELLITE 31 superalloys and others (see for example U.S. Pat. Nos.
4,582,548 and 4,643,782). The chamber C can have a vacuum
(subambient pressure) of about 100 microns and below, such as about
1 to about 10 microns, therein or a substantially oxygen-free
protective atmosphere, such as inert gas, nitrogen, and the like
that is non-reactive with the melted superalloy. The protective
atmosphere may be present in chamber C at a partial pressure less
than atmospheric pressure, at or near atmospheric pressure, or at a
positive pressure greater than atmospheric pressure for melting a
superalloy charge.
[0017] The melting crucible assembly 10 is shown including an
induction coil 12 disposed about a refractory host crucible 14 and
a refractory liner body 16 disposed in the host crucible and
functioning a melting vessel in which a solid charge CH of a
metallic material is heated and melted. The induction coil 12 is
supported on a metal or other support tray 13, which is rotatable
about axis A of a shaft 13a connected to the support tray to
position the crucible assembly in a near horizontal position to
receive a solid metallic charge (e.g. a solid ingot or billet) CH
to be melted and to an upstanding position where the solid metallic
charge is melted in the refractory liner body (melting vessel) 16
by energizing the induction coil 12. In lieu of using induction
coil 12 to heat and melt the metallic charge in the refractory
liner body, electrical resistance heating/melting, gas fired
heating/melting, electron beam heating/melting, or any other means
for heating and melting the metallic charge in the refractory liner
body 16 can be cooperatively positioned in chamber C relative to
the metallic charge in practice of the invention.
[0018] The host crucible 12 resides in a bed of packed refractory
grog particulates 18. The grog particulates 18 in turn are received
in refractory shell 20 applied to the interior of the induction
coil 12. The refractory shell 20 can be formed by manually applying
a refractory mud or grout to the interior of the induction coil 12
and hardening the refractory mud by curing a resin binder or other
type of binder therein in conventional manner. The refractory shell
20 is first formed on the interior of the induction coil 12. Then,
the bottom of grog particulates 18 is placed on the bottom of shell
20 followed by positioning of the host crucible 14 on the grog
particulates 18. Additional grog particulates then are introduced
and packed into the annular space between the upstanding wall of
the host crucible 14 and the upstanding wall of the refractory
shell 20 with the grog particulates topped off with a layer 22 of
thermal insulation, such as KAOWOOL insulation.
[0019] The disposable refractory liner body (melting vessel) 16 is
received in the host crucible 14 in a manner that the liner body 16
can be readily placed in the host crucible and subsequently removed
from the host crucible after a metallic charge has been melted and
poured from the crucible assembly. The refractory liner body 16
thus comprises a disposable (non-reusable or throw-away) liner body
that is used only one time to melt a metallic charge, then removed,
and replaced with a clean, new refractory liner body 16 in the host
crucible. The used (spent) refractory liner body 16 will contain a
small amount of the unpoured, melted metallic charge with dross and
other contaminants such that the used (spent) liner body is
discarded and not reused.
[0020] The refractory liner body (melting vessel) 16 can comprise
any suitable refractory material selected in dependence on the
metal or alloy to be melted therein. For example, for purposes of
illustration and not limitation, in melting a conventional nickel
base superalloy, the refractory body liner 16 can comprise alumina
silicate ceramic. The host crucible 14 can comprise zircon or
alumina silicate ceramic, while the grog particulates can comprise
zirconia particles of -10+35 mesh size meaning the grog particles
are less than 10 mesh and greater than 35 mesh size using U.S.
Standard Sieve system. The refractory shell 20 can comprise
castable alumina. The invention is not limited to any particular
refractory materials which, as mentioned, are selected in
dependence on the metal or alloy to be melted in the liner body
16.
[0021] The disposable (non-reusable), refractory liner body
(melting vessel) 16 is self-supporting in that it supports its own
weight as well as the weight the metallic charge melted therein at
the particular melting temperature employed without the need for
any mechanical support from the host crucible 14, which serves only
to receive and position the liner body 16.
[0022] For purposes of illustration and not limitation, the
refractory liner body 16 is shown having a cylindrical tubular
shape with a closed end, although any suitable body shape can be
used. The liner body 16 is received with radial clearance G in the
host crucible 14 such that the liner body 16 can be readily placed
in the host crucible and subsequently removed from the host
crucible after a metallic charge has been melted and poured from
the crucible assembly. To this end, the outer diameter of the liner
body 16 is less than the inner diameter of the cylindrical side
wall 14a of the host crucible 14. The liner body 16 is not
connected to the host crucible 14 other than being received
therein.
[0023] The refractory liner body 16 includes annular, cylindrical
side wall 16a and an integral bottom wall 16b that closes off the
end the liner body to form an internal chamber 16c in the liner
body 16. The liner body includes an integral partition wall 16d
that extends downwardly in the internal chamber 16c to define or
provide a melting chamber section MS and a pouring chamber section
PS communicated to one another at a location disposed below the
existing level of melted metallic charge (melt level) in the liner
body. The liner body 16 includes integral walls 16w that intersect
with partition wall 16d to form pouring chamber section PS. For
purposes of illustration and not limitation, the partition wall 16d
is shown terminating at its lowermost end a distance above the
bottom wall 16b such that a through-passage 16p is formed between
the melting chamber section MS and a pouring chamber section PS for
flow of clean melted metallic material from the melting chamber
section MS to the pouring chamber section PS. Alternatively, the
partition wall may include openings (not shown) extending
therethrough to this same end.
[0024] The partition wall 16d is configured to form a scallop or
recess 16r along the side thereof facing the melting chamber
section MS. The recess 16r widens in the direction toward the
lowermost end of the partition wall as best shown in FIG. 4. This
recess 16r is adapted to receive and position a cylindrical ingot
or billet of solid metallic charge to be melted. In particular, the
melting crucible assembly 10 can be tilted to place the liner body
16 in a near horizontal position. The cylindrical ingot or billet
then can be placed in the recess 16r on partition wall 16d, FIG. 6.
The melting crucible assembly 10 then can be tilted to place the
liner body 16 in an upstanding vertical position for melting of the
ingot or billet.
[0025] The refractory liner 16 includes a cover 16e that overlies
the partition wall 16d and is connected to the uppermost end of the
partition wall 16d by ceramic cement for example. The cover 16e
includes a discharge or pouring opening 160 through which melted
metallic material in the pouring chamber section PS is poured when
the crucible assembly 10 is tilted to this end by rotation of
support tray 13 by any suitable rotary actuator (not shown)
connected to shaft 13a, FIG. 1.
[0026] The partition wall 16d is positioned and configured such
that clean melted metallic charge below the existing melt level in
melting chamber section MS flows to the pouring chamber section PS
when the melting crucible assembly 10 is tilted, while dross and
other contaminants floating on the melt surface in the melting
chamber section MP remain confined in that chamber section. Use of
a vacuum or protective atmosphere in chamber C together with a
clean, new refractory liner body 16 for melting each respective
metallic charge as well as the flow of the melted metallic charge
from the melting chamber section MS to the pouring chamber section
PS under the partition wall 16d reduces the amount of dross and
other contaminants that will be poured from the pouring chamber
section into a mold M, such as an investment mold, that will be
positioned beneath the melting crucible assembly 10 in chamber C to
receive the melted metallic charge as described, for example, in
U.S. Pat. No. 5,226,946, which is incorporated herein by
reference.
[0027] The cylindrical liner body comprising sidewall 16a and
bottom wall 16b can be made using conventional ceramic fabrication
techniques that include pressed powder and sintering. The walls
16d, 16w and cover 16e are similarly made and connected to the
cylindrical body by cementing.
[0028] Although the invention has been described in detail above
with respect to the refractory liner body 16 being disposed in host
crucible 14 that resides in refractory particulates 18 and
refractory shell 20, the invention is not so limited. The
refractory liner body 16 can be used alone as a melting vessel and
surrounded by induction coil 12 or otherwise cooperatively
positioned relative to any other heating means such as electrical
resistance heating elements, gas fired heating elements, electron
beam(s) and the like, that can heat and melt the metallic charge CH
residing therein as illustrated in FIG. 8. The refractory liner
body 16 used as a melting vessel is tilted by rotating tray 13 to
pour melted metallic charge therefrom such as, for example, into a
mold. Moreover, although the invention is described above with
respect to certain embodiments, those skilled in the art will
appreciate that modifications and changes can be made therein
without departing from the spirit and scope of the invention set
forth in the appended claims.
* * * * *