U.S. patent number RE32,932 [Application Number 07/217,610] was granted by the patent office on 1989-05-30 for cold hearth refining.
This patent grant is currently assigned to A Johnson Metals Corporation. Invention is credited to Charles H. Entrekin, Howard R. Harker.
United States Patent |
RE32,932 |
Harker , et al. |
May 30, 1989 |
Cold hearth refining
Abstract
In the particular embodiment of an electron beam cold hearth
refining arrangement described in the specification, two separate
hearth segments are disposed at right angles to each other and raw
material is supplied to a melt area at the end of the first hearth
segment remote from the second hearth segment. Molten material is
poured from the opposite end of the first hearth segment into the
adjacent end of the second hearth segment and refined molten
material is poured into a mold from the opposite end of the second
hearth segment. To prevent spattering of unrefined material into
the mold or the adjacent refining area of the second hearth segment
a baffle is positioned in the angle between the two mold segments.
0013
Inventors: |
Harker; Howard R. (Malvern,
PA), Entrekin; Charles H. (Coatesville, PA) |
Assignee: |
A Johnson Metals Corporation
(Lionville, PA)
|
Family
ID: |
26695917 |
Appl.
No.: |
07/217,610 |
Filed: |
July 1, 1988 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
22430 |
Mar 6, 1987 |
|
|
|
Reissue of: |
102276 |
Sep 28, 1987 |
04750542 |
Jun 14, 1988 |
|
|
Current U.S.
Class: |
164/506;
164/512 |
Current CPC
Class: |
C22B
9/228 (20130101); F27B 3/08 (20130101); F27B
3/18 (20130101); F27B 3/20 (20130101); F27D
99/0006 (20130101); B22D 27/00 (20130101); F27D
2099/003 (20130101) |
Current International
Class: |
C22B
9/22 (20060101); C22B 9/16 (20060101); B22D
027/02 () |
Field of
Search: |
;164/469,494,495,506,508,512,514 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lin; Kuang Y.
Attorney, Agent or Firm: Brumbaugh, Graves, Donohue &
Raymond
Parent Case Text
This application is a continuation of application Ser. No. 022,430,
filed on Mar. 6, 1987, now abandoned.
Claims
We claim:
1. An electron beam refining furnace comprising hearth means
including first and second elongated hearth segments disposed at an
angle with respect to each other, a mold to receive molten material
after passage through the first and second hearth segments, supply
means for introducing material to be refined to a melting area
adjacent to one end of the first hearth segment and horizontally
spaced from the mold, connecting means providing for flow of molten
material between the opposite end of the first hearth segment and
one end of the second hearth segment, means for transferring
refined material from the opposite end of the second hearth segment
into the mold, and shield means disposed between the melting area
of the first hearth segment and the mold so that a vertical plane
extending between the melting area of the first hearth segment and
the mold intersects the shield means at a location laterally spaced
from a vertical plane containing the melting area and the path of
molten material between the hearth segments, the shield means being
oriented at an angle to the horizontal to intercept molten material
spattered in a generally horizontal direction from the melting area
toward the mold.
2. An electron beam refining furnace according to claim 1 wherein
the first hearth segment is at a higher level than the second
hearth segment and the connecting means comprises a pouring lip at
the end of the first hearth segment adjacent to the second hearth
segment.
3. An electron beam refining furnace according to claim 1 wherein
the second hearth segment includes a refining area and wherein the
shield means is disposed so that a straight line extending between
the melt area of the first hearth segment and the refining area of
the second hearth segment intersects the shield means at a location
laterally spaced from the first and second hearth segments.
4. An electron beam refining furnace according to claim 1 wherein
the first and second elongated hearth segments are disposed
substantially at right angles to each other, the melt area of the
first hearth segment is at the end of the segment remote from the
second hearth segment, the mold is disposed adjacent to the end of
the second hearth segment remote from the first hearth segment and
the shield means is disposed in the corner formed between the first
and second hearth segments.
5. An electron beam refining furnace according to claim 1 wherein
the first and second hearth segments are arranged to subject the
molten material passing through them to different refining
conditions. .Iadd.6. A cold hearth refining furnace comprising
hearth means including first and second elongated hearth segments
disposed at an angle with respect to each other, a mold to receive
molten material after passage through the first and second hearth
segments, supply means for introducing material to be refined to a
melting area adjacent to one end of the first hearth segment and
horizontally spaced from the mold, connecting means providing for
flow of molten material between the opposite end of the first
hearth segment and one end of the second hearth segment, means for
transferring refined material from the opposite end of the second
hearth segment into the mold, and shield means disposed between the
melting area of the first hearth segment and the mold so that a
vertical plane extending between the melting area of the first
hearth segment and the mold intersects the shield means at a
location laterally spaced from a vertical plane containing the
melting area and the path of molten material between the hearth
segments, the shield means being oriented at an angle to the
horizontal to intercept molten material spattered in a generally
horizontal direction from the melting area toward the mold.
.Iaddend.
.Iadd.7. A cold hearth refining furnace according to claim 6
wherein the first hearth segment is at a higher level than the
second hearth segment and the connecting means comprises a pouring
lip at the end of the first hearth segment adjacent to the second
hearth segment. .Iaddend. .Iadd.8. A cold hearth refining furnace
according to claim 6 wherein the second hearth segment includes a
refining area and wherein the shield means is disposed so that a
straight line extending between the melt area of the first hearth
segment and the refining area of the second hearth segment
intersects the shield means at a location laterally spaced from the
first and second hearth segments. .Iaddend. .Iadd.9. A cold hearth
refining furnace according to claim 6 wherein the first and second
elongated hearth segments are disposed substantially at right
angles to each other, the melt area of the first hearth segment is
at the end of the segment remote from the second hearth segment,
the mold is disposed adjacent to the end of the second hearth
segment remote from the first hearth segment and the shield means
is disposed in the corner formed between the first and second
hearth segments. .Iaddend. .Iadd.10. A cold hearth refining furnace
according to claim 6 wherein the first and second hearth segments
are arranged to subject the molten material passing through them to
different refining conditions. .Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to .[.electron beam.]. cold hearth refining
of metals such as titanium alloys which must be completely free of
unrefined, inclusions and, more particularly, to a new and improved
.[.electron beam.]. cold hearth refining furnace which is
especially adapted to prevent contamination of refined metal.
In certain applications wherein metals such as titanium alloys
which have been refined by .[.electron beam.]. cold hearth refining
are used in aircraft engine parts, the presence of even the tiniest
amounts of unrefined inclusions in the refined ingot is severly
detrimental. Since such inclusions may, for example, result in
fracture and disintegration of aircraft engine parts rotating at
very high speed they should be completely avoided.
In conventional .[.electron beam.]. cold hearth refining of metals
such as titanium alloys, a water cooled hearth is supplied with
lumps or pieces of titanium sponge or machine turnings of titanium
alloy consisting of scrap from the manufacture of titanium alloy
parts. This material is introduced by gravity feed at one end of a
cooled elongated hearth in .[.an electron beam.]. .Iadd.a
.Iaddend.furnace in which the material is melted and refined by
electron beam .Iadd.or plasma .Iaddend.impingement. The refined
molten material is poured from the opposite end of the hearth into
a cylindrical mold where it forms a vertically disposed cylindrical
ingot that is withdrawn downwardly within the mold as it
solidifies.
In conventional .[.electron beam.]. cold hearth furnaces used for
refining of titanium alloy or the like, the raw material often
includes vaporizable contaminants such as chlorine in titanium
sponge and oil or moisture in machine turnings. As such materials
are introduced into the melt area of the hearth and are heated by
the molten metal and by an electron beam, .Iadd.for example,
.Iaddend.the vaporizable contaminants frequently produce relatively
violent eruptions in the molten metal being refined. Such eruptions
have been found to cause both molten and unmelted material from the
melt area to be spattered toward other areas of the electron beam
furnace including the casting area where the refined ingot is being
molded. As a result, it is possible that unrefined metal containing
undesirable inclusions such as titanium nitrides or tungsten
carbides, for example, is introduced into the mold and thereby
incorporated into the cast ingot and into any final product
produced from the ingot, such as a jet engine compressor disc, for
example.
Heretofore the provision of a vertical shield over the molten
material at the end of the hearth adjacent to the casting area has
been proposed in order to block such spattering of material into
the mold. With such arrangements, however, unmelted material
spattered by eruptions and prevented by the shield from entering
the casting area directly can be deflected downwardly from the
shield into the molten material at the point where it passes from
the hearth into the mold. Furthermore, vaporized material and
spattered molten material may accumulate and solidify on the shield
and occasionally portions of such solid material containing
contaminating inclusions may drop from the shield into the refined
molten material as it passes from the hearth into the mold.
Accordingly, it is an object of the present invention to provide a
new and improved .[.electron beam.]. cold hearth refining
arrangement which overcomes the abovementioned disadvantages of the
prior art.
Another object of the invention is to provide a new and improved
.[.electron beam.]. cold hearth refining furnace which provides
greater assurance that refined metal will be free of undesirable
inclusions.
SUMMARY OF THE INVENTION
These and other objects of the invention are attained by providing
an elongated hearth arrangement having hearth segments which extend
at an angle to each other, a supply device for introducing raw
material to a melt area at one end of one of the hearth segments, a
mold for receiving refined material from the opposite end of
another segment, and a shield disposed in the angle between the
hearth segments at a location such that a straight line extending
between the melt area and the mold intersects the shield at a
position laterally spaced from both of the hearth segments. In a
preferred arrangement, the two hearth segments are separate hearths
disposed at right angles to each other at different levels so that
refined molten metal from the first hearth is poured into the
adjacent end of the second hearth.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will be apparent
from a reading of the following description in conjunction with the
accompanying drawings in which:
FIG. 1 is a schematic view in longitudinal section illustrating a
representative conventional electron beam cold hearth refining
arrangement; and
FIG. 2 is a schematic plan view illustrating a typical electron
beam cold hearth refining arrangement in accordance with the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the conventional cold hearth electron beam refining arrangement
shown in FIG. 1, a hearth 10 comprises a hearth bed 11 containing
cooling pipes 12 through which water or another cooling liquid may
be circulated. At the inlet end of the hearth, a chute 13 directs
pieces 14 of the raw material to be refined, such as titanium
sponge or titanium alloy machine turnings, into the hearth and a
series of electron beam guns 15 disposed above the hearth produces
controllable beams of electrons 16 which can be directed to desired
areas of the hearth to heat the material to be refined in a desired
manner. One of the beams 16 is concentrated on the raw material 14
at the melt area 17 of the hearth so as to melt the raw material,
and other electron beams 16 are controlled so as to refine the
molten metal during its passage from the melt area 17 to a pouring
lip 18 at the other end of the hearth. .Iadd.Alternatively, other
energy sources, such as plasma torches, may be used in place of
electron beam guns. .Iaddend.
As a result, the raw material introduced into the hearth forms a
molten pool 19 which flows from the melt area 17 to the lip 18.
Because the hearth bed 11 is cooled by liquid flowing through the
pipes 12, a solid skull 20 of the molten material 19 in the pool
forms on the inner surface of the hearth bed, protecting it from
degradation by the molten material.
As the molten mater0155 ral 19 flows through the hearth, it is
completely melted and refined, producing a stream 21 of molten
refined material which pours from the pouring lip 18 into a
vertical mold 22 containing cooling pipes 23. The molten metal then
cools in the mold 22, forming an ingot 24 which is gradually moved
downwardly within the mold in a conventional manner as indicated by
the arrow. Another electron beam gun 25 directs a beam of electrons
26 in a controlled manner toward the surface of the molten material
27 within the mold so as to control the cooling and solidification
of that material into the ingot 21 in a desired manner. The entire
arrangement is, of course, contained within a sealed enclosure (not
shown) and maintained at a high vacuum in the conventional
manner.
As the raw material 14 is introduced into the melt area of the
hearth, it frequently carries with it certain contaminants which
are volatile at the temperature of the molten material 19 and which
are therefore removed during the refining process. For example,
chlorine may be contained within titanium sponge particles and
liquids such as oil and water may be carried by titanium alloy
turnings as they are poured from the chute 13 into the melt area
17. Frequently, the introduction of such volatile materials into
the molten material 19 causes rapid vaporization of the volatile
material at or below the surface of the molten material, producing
eruptions which spatter both molten and unmelted material in all
directions.
In conventional hearth arrangements such eruptions may spatter
unrefined material directly from the melt area 17 of the hearth
into the mold 22 as indicated by the dotted line paths 28 in FIG.
1. Although the electron beam gun 25 directs a beam of electrons 26
at the surface of the molten material 27 in the mold, that material
is generally at a lower temperature than the material in the hearth
and the electron beam 26 will normally not be sufficient to refine
any unrefined material within the mold. As a result, the spattered
unrefined metal, containing inclusions such as titanium nitrides or
tungsten carbides, may be incorporated into the ingot 20224 4,
contaminating the final product made from that ingot with
detrimental results to that product.
In certain conventional .[.electron beam.]. cold hearth furnaces, a
shield may be placed above the outlet end of the hearth, as
indicated by the dotted outline 29 in FIG. 1, to block material
spattered from the melt area from passing directly into the mold
22. With such arrangements, however, unrefined material spattered
from the melt area 17 toward the mold which strikes the shield 29
is frequently deflected downwardly to the surface of the molten
material 19 as it is being poured into the mold so that it is
carried directly into the mold with the molten material. Moreover,
vaporized material and spattered molten material solidifies on the
surface of the shield and portions of such solidified material may
be dislodged so that they fall directly into the molten material
being poured with the same detrimental result.
In accordance with the present invention, the possibility of
introducing such unrefined material into a mold is eliminated by
providing a segmented hearth in the manner shown in FIG. 2. In this
arrangement, a first hearth segment 30 is in the form of an
elongated hearth having an inlet end at which raw material, such as
titanium sponge or titanium alloy turnings 14, is introduced from a
chute 13 into the melt area 17. Electron beam guns, similar to the
guns 15 shown in FIG. 1 but not shown in FIG. 2, are arranged above
the hearth segment 30 to melt the raw material in the melt area 17
and to refine the molten material 31 as it passes toward a pouring
lip 32 at the outlet end of the hearth segment 30. A second
elongated hearth segment 33, positioned at a lower level than the
hearth segment 30 and at right angles to the segment 30 receives
molten material 34 from the pouring lip 32. One or more additional
electron guns, similar to the guns 15 of FIG. 1 but not illustrated
in FIG. 2, direct electron beams toward the surface of the molten
material in a refining area 35 of this hearth segment to complete
the refining of the material as it flows through the hearth
segment. At its outlet end, the hearth segment 33 has a pouring lip
36 through which refined molten metal 37 is poured into a mold 38
to produce a refined ingot in the same manner described above with
respect to FIG. 1. The mold 38 as illustrated in FIG. 2 has a
circular cross section but it may, instead, have any other desired
cross-sectional configuration, such as rectangular, for
example.
To prevent introduction of unrefined material into the mold 38 in
accordance with the invention, a solid shield 39 is mounted in the
angle between the first and second hearth segments 30 and 33 in
such manner that a direct line between the melt area 17 at the
inlet to the hearth segment 30 and either the refining area 35 of
the second hearth segment or the mold 38 intersects the shield 39.
In addition, as shown in FIG. 2, the shield 39 is laterally
displaced from the hearth segments so that molten material
spattered against it or vaporized or spattered material which has
solidified on its surface will not fall into the molten material in
either the first hearth segment 30 or the second hearth segment 33.
Although only two hearth segments are shown in FIG. 2, any number
of hearth segments may, of course, be used as long as a shielding
arrangement is provided to prevent material spattered from the melt
area from reaching the mold.
With this arrangement, metals such as titanium alloy can be refined
in .[.an electron beam.]. .Iadd.a .Iaddend.cold hearth furnace
without concern over possible inclusions which might be spattered
into the mold at the end of the hearth by the introduction of
materials containing vaporizable contaminants at the melt area of
the hearth. Furthermore, when two or more hearth segments at
different levels are used, as in the embodiment shown in FIG. 2,
two separate hearth skulls are formed so that thermal expansion and
contraction of the skulls can occur in each hearth segment
independently of the conditions in the other hearth segment. As a
result, different refining conditions can be used in the hearth
segments and improved stirring of the material being refined is
provided by the cascading of molten material from one segment to
the other so that improved refining of the material can be
obtained.
Although the invention has been described herein with reference to
a specific embodiment, many modifications and variations therein
will readily occur to those skilled in the art. Accordingly, all
such variations and modifications are included within the intended
scope of the invention as defined by the following claims.
* * * * *