U.S. patent application number 11/333430 was filed with the patent office on 2007-07-19 for method and apparatus for preheating and feeding material.
This patent application is currently assigned to RMI TITANIUM COMPANY. Invention is credited to Michael P. Jacques, Frank P. Spadafora, Kuang-O Yu.
Application Number | 20070163387 11/333430 |
Document ID | / |
Family ID | 38261890 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163387 |
Kind Code |
A1 |
Spadafora; Frank P. ; et
al. |
July 19, 2007 |
Method and apparatus for preheating and feeding material
Abstract
A casting furnace for preheating and melting solid feed material
includes a melting chamber with a melting hearth therein and a feed
chamber in fluid communication with the melting chamber for
conveying the solid material into the melting chamber. A heat
source melts the feed material within the melting hearth and
produces surplus heat used to preheat the solid feed material.
Preferably, gas is heated by the heat source and moved into the
feed chamber to preheat the feed material while it is conveyed
toward the melting hearth. The heated gas is recycled back into the
melting chamber to be re-heated therein and reused to preheat
additional feed material in the feed chamber. Where the heat source
in the melting chamber includes a plasma torch, the gas is recycled
via the plasma torch, which ionizes the gas to create a plasma
plume for melting the solid material.
Inventors: |
Spadafora; Frank P.; (Niles,
OH) ; Jacques; Michael P.; (Canton, OH) ; Yu;
Kuang-O; (Highland Heights, OH) |
Correspondence
Address: |
SAND & SEBOLT
AEGIS TOWER, SUITE 1100
4940 MUNSON STREET, NW
CANTON
OH
44718-3615
US
|
Assignee: |
RMI TITANIUM COMPANY
Niles
OH
44446
|
Family ID: |
38261890 |
Appl. No.: |
11/333430 |
Filed: |
January 17, 2006 |
Current U.S.
Class: |
75/585 |
Current CPC
Class: |
F27B 9/10 20130101; F27B
3/085 20130101; F27B 3/20 20130101; F27B 19/02 20130101; C22B
34/1295 20130101; F27B 3/045 20130101; F27B 9/243 20130101; F27B
9/38 20130101; C22B 9/226 20130101; F27D 17/004 20130101 |
Class at
Publication: |
075/585 |
International
Class: |
C22B 9/00 20060101
C22B009/00 |
Claims
1. A method comprising the steps of: preheating solid feed material
by moving the solid feed material within a melting chamber in a
first direction and moving heated gas within the melting chamber
along the feed material in a second direction generally opposite
the first direction; moving the heated solid feed material into a
melting cavity of a melting hearth disposed within the melting
chamber; and melting the solid material in the melting cavity of
the melting hearth.
2-20. (canceled)
21. The method of claim 1 further comprising the step of feeding
solid feed material into the melting chamber through a feed entry
port formed in a sidewall bounding the melting chamber; and wherein
the step of preheating comprises the step of preheating solid feed
material by moving the solid feed material in the first direction
from the feed entry port toward the melting hearth and moving the
heated gas in the second direction from adjacent the melting hearth
to adjacent the feed entry port.
22. The method of claim 21 wherein the step of preheating comprises
the step of preheating solid feed material by moving the solid feed
material in the first direction from the feed entry port to the
melting hearth atop a conveyor assembly disposed in the melting
chamber and having a first end adjacent the feed entry port and a
second opposed end adjacent the melting hearth.
23. The method of claim 22 wherein the step of preheating comprises
the step of preheating solid feed material by moving the solid feed
material atop an upper surface of the conveyor assembly onto an
upper surface of the melting hearth adjacent the melting cavity and
the upper surface of the conveyor assembly.
24. The method of claim 23 wherein the step of moving the heated
solid feed material comprises the step of sliding the heated solid
feed material along the upper surface of the melting hearth to move
it into the melting hearth.
25. The method of claim 22 wherein the step of moving the solid
feed material in the first direction comprises the step of moving
the solid feed material in the first direction from the feed entry
port to the melting hearth atop one of a conveyor belt assembly and
a walking table disposed in the melting chamber.
26. The method of claim 22 further comprising the step of pushing
solid feed material through the feed entry port onto the first end
of the conveyor assembly.
27. The method of claim 26 wherein the step of pushing comprises
the step of pushing solid feed material through the feed entry port
on a platform extending from outside the chamber into the entry
port and adjacent the first end of the conveyor assembly.
28. The method of claim 21 wherein the step of moving the heated
gas comprises the step of moving the heated gas in the second
direction from adjacent the melting hearth to a gas exit port
formed in the sidewall adjacent the feed entry port; and further
comprising the step of moving the gas out of the melting chamber
through the gas exit port.
29. The method of claim 28 further comprising the step of recycling
the gas which exited through the gas exit port back into the
melting chamber adjacent the melting hearth and distal the feed
entry port.
30. The method of claim 29 wherein the step of melting comprises
the step of melting the feed material in the melting hearth with a
first plasma torch positioned above the melting hearth distal the
feed entry port; and wherein the step of recycling comprises the
step of recycling the gas back into the melting chamber through the
plasma torch.
31. The method of claim 28 further comprising the steps of pouring
molten material from the melting hearth into a mold disposed in the
melting chamber distal the feed entry port; and recycling the gas
which exited through the gas exit port back into the melting
chamber adjacent the mold.
32. The method of claim 31 further comprising the step of heating
material in the mold with a plasma torch positioned above the mold
distal the feed entry port; and wherein the step of recycling
comprises the step of recycling the gas back into the melting
chamber through the plasma torch.
33. The method of claim 1 wherein the step of moving the heated
solid feed material comprises the step of sliding the heated solid
feed material along an upper surface of the melting hearth adjacent
the melting cavity to move it into the melting hearth.
34. The method of claim 33 wherein the step of preheating comprises
the step of preheating solid feed material by moving the solid feed
material with a conveyor assembly disposed in the melting chamber
on an upper surface of the conveyor assembly which is adjacent the
upper surface of the melting hearth; and further comprising the
step of transferring the preheated solid feed material from the
upper surface of the conveyor assembly onto the upper surface of
the melting hearth.
35. The method of claim 34 wherein the step of transferring
comprises the step of contacting both upper surfaces simultaneously
with a piece of the preheated solid feed material.
36. The method of claim 1 further comprising the step of pouring
molten material from the melting hearth into a mold disposed in the
melting chamber.
37. The method of claim 36 further comprising the step of pouring
molten material from the melting hearth into a continuous casting
mold disposed in the melting chamber.
38. The method of claim 36 further comprising the steps of forming
a molded body with the mold; and removing the molded body from the
melting chamber.
39. The method of claim 38 wherein the step of removing comprises
the step of lowering the molded body from the melting chamber on a
lift.
40. The method of claim 36 further comprising the steps of heating
material in the mold with a plasma torch positioned above the mold;
heating gas within the melting chamber with the plasma torch to
produce heated gas used in the step of preheating.
41. The method of claim 40 further comprising the steps of
recycling the gas back into the melting chamber via the plasma
torch; and generating a plasma plume with the gas.
42. The method of claim 1 wherein the step of melting comprises the
step of melting the feed material in the melting cavity with a
first plasma torch positioned above the melting hearth; and further
comprising the steps of pouring molten material from the melting
hearth into a mold disposed in the melting chamber; heating
material in the mold with a second plasma torch positioned above
the mold; heating gas within the melting chamber with the first and
second plasma torches to produce heated gas used in the step of
preheating.
43. The method of claim 42 further comprising the steps of
recycling the gas back into the melting chamber via the first and
second plasma torches; and generating a plasma plume in each torch
with the gas.
44. A method comprising the steps of: preheating solid feed
material by moving the solid feed material within a melting chamber
from a feed entry port formed in a sidewall bounding the melting
chamber toward a melting hearth disposed in the melting chamber and
moving heated gas from adjacent the melting hearth out of the
melting chamber through a gas exit port formed in the sidewall
adjacent the feed entry port; moving the preheated solid feed
material into the melting hearth; and melting the preheated solid
feed material in the melting hearth.
45. The method of claim 44 wherein the step of preheating comprises
the step of preheating by moving the solid feed material on a
conveyor assembly in the melting chamber having a first end
adjacent the feed entry port and a second opposed end adjacent the
melting hearth and moving heated gas from the second end to the
first end.
46. The method of claim 44 further comprising the step of pouring
molten material from the melting hearth into a mold disposed in the
melting chamber; and wherein the step of moving heated gas
comprises the step of moving heated gas from adjacent the mold out
of the melting chamber through the gas exit port.
47. A method comprising the steps of: preheating solid feed
material within a melting chamber in which a melting hearth is
disposed; sliding the preheated solid feed material along an upper
surface of the melting hearth adjacent a melting cavity thereof to
move it into the melting cavity; and melting the preheated solid
feed material in the melting cavity.
48. The method of claim 47 wherein the step of preheating comprises
the step of preheating solid feed material by moving the solid feed
material with a conveyor assembly disposed in the melting chamber
on an upper surface of the conveyor assembly which is adjacent the
upper surface of the melting hearth; and further comprising the
step of transferring the preheated solid feed material from the
upper surface of the conveyor assembly onto the upper surface of
the melting hearth.
49. The method of claim 48 wherein the step of transferring
comprises the step of contacting both upper surfaces simultaneously
with a piece of the preheated solid feed material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The invention relates generally to a furnace for melting
metals and other materials in which a solid feed material is
preheated. More particularly, the invention relates to such a
furnace wherein the solid feed material is preheated by heated gas
from within the melting chamber. Specifically, the invention
relates to such a furnace in which a plasma torch used for melting
the material produces the heated gas and wherein the gas is cooled
and recycled for re-use by the plasma torch.
[0003] 2. Background Information
[0004] Furnaces for melting metal and other materials typically
have a melting chamber with a melting hearth disposed therein in
which the metal or other material is melted. Various types of heat
sources provide the heat in order to melt the material within the
melting hearth. It would be helpful to preheat the solid feed
material which is fed into the melting hearth in order to reduce
the total melting time, thereby increasing productivity. An
increased melt rate can also increase the depth and size of the
molten pool, the super heat of the molten material, liquid metal
mixing and the capability for chemistry control. The increased melt
rate would also increase the probability of removing defects such
as high density inclusions (HDIs) and improve the surface quality
in continuously casting ingots or slabs. The present invention
provides such preheating and the above-listed benefits.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention provides a method comprising the steps
of preheating solid feed material; moving the heated solid feed
material into a melting hearth disposed within a melting chamber;
and melting the solid material in the melting hearth.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0006] FIG. 1 is a sectional view taken from the side of the
furnace showing the preheating system of the present invention.
[0007] FIG. 2 is similar to FIG. 1 and shows an alternate feeding
mechanism.
[0008] Similar numbers refer to similar parts throughout the
specification.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The furnace and preheating system of the present invention
is indicated generally at 10 in FIG. 1; and a second embodiment is
indicated generally at 100 in FIG. 2. While furnace 10 is
configured as a plasma arc melting furnace, various concepts of the
invention are applicable to other types of furnaces as well.
Furnace 10 includes an insulated melting chamber 12 with a
withdrawal chamber 14 disposed therebelow and in fluid
communication therewith, and an insulated feed chamber 16 which is
disposed beside melting chamber 12 and in fluid communication
therewith. A melting hearth 18 which defines a melting cavity 20
and a continuous casting mold 22 are disposed within melting
chamber 12. A lift 24 is disposed below mold 22, is partially
within withdrawal chamber 14 and is movable up and down as shown by
Arrow A into and out of melting chamber 12. First and second heat
sources which are preferably in the form of first and second plasma
torches-26 and 28 extend from above melting chamber 12 through an
upper wall thereof and into chamber 12 for respectively providing
heat above mold 22 and melting hearth 18. More particularly, second
torch 28 provides heat to melt pieces 30 of solid feed material
which are moved into melting cavity 20 as indicated at Arrow B to
form molten material 32 within cavity 20 which is subsequently
poured or otherwise moved as indicated at Arrow C into mold 22 to
produce a molded body in the form of an ingot 33 as lift 24 is
lowered. First torch 26 provides heat to molten material 32 within
mold 22 in order to control the solidification rates and so forth.
While pieces 30 of feed material are typically metal, other
materials are contemplated as well. Furnace 10 is suitable for
melting titanium alloys or superalloys.
[0010] With continued reference to FIG. 1, feed chamber 16 has a
first end 34 adjacent which it is connected to melting chamber 12
and a second opposed end 36 distal melting chamber 12. Feed chamber
16 defines an entrance opening 38 adjacent second end 36 for
receiving pieces 30 of solid feed material from outside feed
chamber 16. Furnace 10 includes a feed assembly 40 comprising an
input mechanism in the form of an actuator 42 which is disposed
external to feed chamber 16 and includes a piston 44 which is
moveable back and forth as indicated by Arrow D. Feed assembly 40
also includes a conveyor assembly 46 disposed within feed chamber
16 and extending partially into melting chamber 12. Conveying
assembly 46 includes a conveyor belt 48 which is revolvingly
mounted on a pair of rotatable members 50A and 50B disposed at
respective opposed ends of conveying assembly 46. Input mechanism
42 includes a substantially horizontal platform 45 which is aligned
with a substantially horizontal upper portion 52 of conveyor belt
48. Feed chamber 16 includes a heating passage 54 through which
pieces 30 of solid feed material are moved as indicated by Arrows E
from entrance opening 38 to melting hearth 18. More particularly,
piston 44 of actuator 42 is operated to move pieces 30 of solid
feed material from a top platform 45 onto upper portion 52 of
conveyor belt 48 whereby operation of conveying assembly 46 moves
pieces 30 as indicated at Arrows E along upper portion 52 to feed
pieces 30 into melting cavity 20 of hearth 18.
[0011] With continued reference to FIG. 1 and in accordance with a
feature of the invention, melting chamber 12 and feed chamber 16
are part of a recirculation pathway 56 which includes various
conduits or ducts 58, a heat exchanger 60, a scrubber 62 for
removing impurities from gas and a pump 64, all of which are in
fluid communication with one another. Recirculation pathway 56 is
configured to recirculate a gas 66 therethrough so that gas 66 is
heated within melting chamber 12 and moved into feed chamber 16 in
order to heat pieces 30 of solid feed material prior to entering
melting cavity 20 to be melted by torch 28. Gas 66 is typically an
inert gas and when used with plasma torches such as torch 28 is
typically helium or argon or a mixture thereof.
[0012] With reference to FIG. 1, the operation of furnace 10 is
further detailed. Pump 64 is operated to pump gas 66 through a
segment of duct 58 as indicated at Arrows F into second torch 28.
Gas 66 is then moved as indicated at Arrows G through torch 28,
which heats and ionizes gas 66 to generate a plasma plume 68 for
heating and melting pieces 30 and maintaining molten material 32 in
melting hearth 18. Where other plasma torches such as torch 26 are
used, gas 66 may also be circulated through such other plasma
torches as indicated at Arrow G2. The core of plasma plume 68
typically has a temperature on the order of about 10,00.degree. C.
and gas 66 within chamber 12 has a temperature typically on the
order of about 1,000.degree. C. Thus, gas 66 becomes a heated gas
within chamber 12 which moves as indicated by Arrows H into and
through heating passage 54 of feed chamber 16 from first end 34
thereof to second end 36 thereof.
[0013] As the heated gas 66 is moved as indicated by Arrows H away
from melting chamber 12, pieces 30 of solid feed material are moved
toward melting chamber 12 in substantially the opposite direction.
Due to the elongated nature of chamber 16, the invention thus takes
advantage of a relatively lengthy heating passage 54 in order to
allow substantial time for the heat exchange between heated gas 66
and pieces 30. The heated gas 66 will of course be substantially
hotter adjacent first end 34 than adjacent second end 36 of feed
chamber 16. The insulated walls of melting chamber 12 and feed
chamber 16 help maintain heated gas 66 as hot as is feasible in
order to better take advantage of the heat exchange between gas 66
and pieces 30.
[0014] Heated gas 66 reaches second end 36 of feed chambers 16 and
exits through a vent or segment of duct 58 as indicated at Arrow J
into heat exchanger 60 and then through another segment of duct 58
as indicated at Arrow K into scrubber 62 and finally through
another segment of duct 58 as indicated at Arrow L back to pump 64
whereby gas 66 has been completely recirculated. Heat exchanger 60
cools gas 66 down to a temperature which is suitable for scrubbing
of gas 66 via scrubber 62, typically at about room temperature.
[0015] With reference to FIG. 2, furnace 100 is described. Furnace
100 is similar to furnace 10 except that furnace 100 includes a
feed assembly 102 which differs from feed assembly 40 of furnace 10
in that assembly 102 includes a conveying assembly 104 which is
different than that of furnace 10. More particularly, conveying
assembly 104 is a walking table suitable for receiving pieces 30
from platform 45 and delivering pieces 30 as shown by Arrows E into
melting cavity 20 of hearth 18. Otherwise, the operation of furnace
100 is the same as furnace 10.
[0016] Thus, furnaces 10 and 100 provide systems that are
configured to preheat solid feed material prior to placing the feed
material in the melting hearth where it is melted. While the
invention contemplates preheating solid feed material by any
mechanism, it also advantageously utilizes the surplus heat
produced by the primary heat sources which are used for melting the
feed material within the melting hearth and melting chamber. It is
contemplated that this surplus heat produced by the primary heat
source within the melting chamber may be transferred to preheat the
solid feed material by means of radiation, convection, conduction
or any combination of these. However, the movement of the heated
gas is a preferred mode of accomplishing this transfer of heat in a
more efficient manner. While the exemplary embodiment preferably
utilizes at least one plasma torch whereby the heated gas is
recirculated for reuse by the plasma torch, it is also contemplated
that gas which is heated by the surplus heat within a melting
chamber may be transferred in other manners in order to preheat
solid feed material. For example, in furnaces which are under a
vacuum to eliminate or substantially eliminate gasses within the
melting chamber, conduits may be configured to pass through a
portion of the melting chamber so that gas passing through such
conduits is heated within the melting chamber by the surplus heat
and then transferred to a separate feed chamber or the like in
order to preheat the solid feed material. Other variations which
are within the scope of the present invention will be evident to
one skilled in the art.
[0017] In the foregoing description, certain terms have been used
for brevity, clearness, and understanding. No unnecessary
limitations are to be implied therefrom beyond the requirement of
the prior art because such terms are used for descriptive purposes
and are intended to be broadly construed.
[0018] Moreover, the description and illustration of the invention
is an example and the invention is not limited to the exact details
shown or described.
* * * * *