Melting of reactive metallic materials

Method and apparatus for melting reactive metallic materials, such as for example titanium base alloys and other reactive alloys, by selective and sequential induction heating of a plurality of solid alloy charge components segregated in a refractory melting vessel in a manner to effect rapid top-to-bottom melting that avoids harmful reaction of the melt with refractory melting vessel material and contamination of the melt.

FIELD OF THE INVENTION 
The present invention relates to method and apparatus for melting reactive 
alloys in high volumes at reduced cost without harmful contamination 
resulting from reactions between the reactive melt and melt containment 
materials. 
BACKGROUND OF THE INVENTION 
Many alloys with high weight percentages of a reactive metal, such as 
titanium, react with air and most common crucible refractories to the 
degree that the alloy is contaminated to an unacceptable extent. As a 
result, it common to melt such alloys in water cooled, metal (e.g. copper) 
crucibles using electric arc or induction to generate heat in the alloy 
charge for melting. U.S. Pat. Nos. 4,738,713 and 5,033,948 are 
representative of such melting techniques. 
Alloys of titanium and aluminum forming intermetallic compounds, such as 
TiAl, have received considerable attention in recent years for use in the 
aerospace and automobile industries in service applications where their 
high strength at elevated temperature and relatively light weight are 
highly desireable. However, the intermetallic alloys contain a majority of 
titanium (e.g. so-called gamma TiAl includes 66 weight % Ti with the 
balance essentially Al) which makes melting and casting without 
contamination difficult and costly. 
The Chandley and Flemings U.S. Pat. No. 5,299,619 describes an improved 
melting and casting technique for reactive metals and alloys, including 
those forming intermetallic compounds, wherein heating and melting of a 
charge of solid titanium in a ceramic crucible is accelerated by a robust 
exothermic reaction with a molten aluminum charge component that is 
separately melted and then introduced to the crucible to contact the 
titanium charge component. Reduced residence time of the melted charge 
components reduces potential contamination of the melt by reaction with 
the crucible materials. 
Unfortunately, titanium based alloys, such Ti-6Al-4V, have insufficent 
aluminum present in the alloy composition to effect the robust exothermic 
reaction with titanium in the melting vessel for practicing the rapid 
melting, reduced contamination technique of U.S. Pat. No. 5,299,619. Since 
such "aluminum poor" titanium based alloys are in widespread use, there is 
a need for a melting method that can provide low cost, rapid melting of 
such "aluminum poor" reactive alloys with reduced contamination of the 
melt. 
It is an object of the present invention to provide method and apparatus 
that satisfy the aforementioned need for a melting method and apparatus 
that can provide low cost, rapid melting, reduced contamination of 
"aluminum poor" titanium base alloys as well as other reactive alloys 
having compositions incapable of a robust exothermic reaction in a melting 
vessel. 
It is another object of the present invention to provide method and 
apparatus for melting reactive metallic materials in a refractory melting 
vessel using selective and sequential induction heating of various solid 
metallic charge components segregated in a refractory crucible in a manner 
to effect top-to-bottom melting of the components that avoids harmful 
contamination of the melt. 
It is another object of the present invention to provide method and 
apparatus useful for melting reactive metallic materials in a refractory 
melting vessel in top-to-bottom manner that eliminates the need for a 
separate melting step of one charge component that heretofore was melted 
first and then added to the vessel. 
SUMMARY OF THE INVENTION 
The present invention provides method and apparatus useful for melting 
reactive metallic materials by selective and sequential induction heating 
of a plurality of solid alloy charge components segregated in a refractory 
melting vessel in a manner to effect rapid top-to-bottom melting that 
avoids harmful reaction of the melt with refractory melting vessel 
material and contamination of the melt. The present invention can be 
practiced to melt reactive metallic materials such as "aluminum poor" 
titanium base alloys as well as other reactive alloys, such as zirconium 
base and iron base alloys, having compositions incapable of robust 
exothermic reaction in a melting vessel. In addition, the present 
invention can be practiced to melt reactive metallic materials, such as 
TiAl and other intermetallic compound-forming alloys, that have 
compositions capable of robust exothermic reaction without the need for a 
separate melting step of one charge component. 
In an illustrative embodiment of the present invention, the higher melting 
point alloying element(s) of a reactive alloy is/are positioned as solid 
charge component(s) in an underlying position, such as in a lower region, 
of a refractory melting vessel and the relatively lower melting point 
alloying element(s) is/are positioned as solid charge component(s) in an 
overlying position such as above the higher melting point charge 
component(s) in the vessel. For example only, to form a Ti-6Al-4V reactive 
melt, relatively high melting point solid titanium and vanadium charge 
components are dispersed together proximate the bottom of the melting 
vessel underneath a lower melting point solid charge component comprising 
at least partially aluminum along with optional lower and/or higher metal 
point metals. Then, the upper portion of the charge is selectively 
induction heated in the melting vessel to increase its temperature above 
that of the lower portion of the charge. Thereafter, both the upper and 
lower portions of the charge are induction heated at higher power input to 
rapidly melt the upper portion of the charge followed by melting of the 
lower portion charge to form a molten alloy in very short melting time, 
such as for example only 1 to 3 minutes, to reduce residence time of the 
melt in the refractory melting vessel. In particular, the upper portion of 
the charge exhibits a higher resisitivty as a result of being preheated to 
a higher temperature and thus generates more heat upon induction heating 
at the higher power input. The lower melting point charge component melts 
first, alloys with the upper portion of the charge, and flows toward the 
bottom of the melting vessel as a result. 
As top-to-bottom melting of the charge components occurs, the molten alloy 
is substantially held away from the side walls of the melting vessel by 
the high induction coil power input so as to reduce adverse reaction 
between the molten alloy and the vessel refractory material. Moreover, the 
bottom center of the higher melting point charge component(s) is the last 
region of the charge to melt and reduces adverse reaction of the molten 
alloy with the refractory material at the bottom of the melting vessel. 
The molten alloy can be cast from the melting vessel using conventional 
countergravity or gravity casting techniques as soon as the melt is at an 
appropriate casting temperature to also reduce residence time and melt 
contamination. 
The present invention is advantgeous in that a wide variety of reactive 
alloys can be rapidly melted with reduced contamination, including myriad 
reactive alloys having compositions incapable of robust exothermic 
reaction in a melting vessel. Morever, there is no need for a separate 
melting step to separately melt one charge component that then must be 
added to the melting vessel, thereby simplifying and reducing the cost of 
melting and casting reactive alloys. In addition, use of selective and 
sequential induction heating of a plurality of solid alloy charge 
components segregated in a refractory melting vessel in a manner to effect 
rapid top-to-bottom melting permits use of conventional crucible 
refractory materials in the melting of reactive alloys, while still 
reducing harmful contamination of the reactive alloy melt. 
These and other advantages and objects of the present invention will be 
better understood from the following detailed description of the invention 
taken with the following drawings.

DESCRIPTION OF THE INVENTION 
The present invention provides method and apparatus for rapidly melting a 
wide variety of reactive metallic materials, such as for example only 
titanium base alloys, zirconium base alloys, and iron base alloys, having 
compositions unsuitable for practicing the rapid melting, reduced 
contamination technique of U.S. Pat. No. 5,299,619 as well as reactive 
alloys, such as TiAl and other intermetallic compound-forming alloys, that 
do have compositions suitable for practicing the patented rapid melting 
technique. Importantly, the latter reactive alloys can be melted pursuant 
to the present invention without the need for the separate melting step. 
Binary, ternary, quaternary, and other higher reactive alloys can be melted 
by practice of the present invention. An exemplary binary alloy comprises 
a titanium and aluminum alloy that includes 66 weight % Ti and balance 
essentially Al and that forms the well known predominantly gamma TiAl 
intermetallic compound. This reactive alloy can be melted pursuant to the 
invention without the need for separately melting of the aluminum alloy 
component. An exemplary ternary alloy can include an alloy of titanium, 
aluminum and another metal, such as the well known Ti-6Al-4V alloy where 
the numbers represent weight %'s of the alloying elements. The Ti-6Al-4V 
alloy has insufficient aluminum to effect the robust exothermic reaction 
with titanium as described in U.S. Pat. No. 5,299,619. Representative 
reactive alloys that can be melted pursuant to the present invention are 
described in the Examples set forth below for purposes of illustration 
only and not limitation. 
Referring to FIGS. 1-2, apparatus for practicing an embodiment of the 
present invention is illustrated as including a mold section 10 and a 
melting section 12 with the mold section 10 disposed above the melting 
section 12 for countergravity casting of the reactive melt upwardly into 
the mold section. A mold container 20 is movable relative to the melting 
section 12 by a hydraulic actuated arm (not shown) as illustrated in U.S. 
Pat. No. 5,042,561, the teachings of which are incorporated herein to this 
end. 
The mold section 10 includes a steel container 20 having a cylindrical 
chamber 20a in which an investment mold 22 having a plurality of mold 
cavities 24 is disposed in a mass 26 of low reactivity particulates. The 
mold 22 rests on an elongated, refractory (e.g. carbon) fill pipe 23 
depending therefrom outside the container 20. The fill pipe 23 is joined 
to the bottom of the mold 22 and extends sealingly through a bottom 
opening in the container 20 as shown, for example, in aforementioned U.S. 
Pat. No. 5,042,561. A mold sprue 28 is communicated to the fill pipe 23 
and to the mold cavities 24 via lateral ingates 31. The investment mold 22 
is formed by the well known lost wax process described in U.S Pat. No. 
5,299,619, the teachings of which are incorporated herein to this end. 
The mold container 20 includes an openable/closeable lid 25 connected to 
the container via a hinge 25a. The lid carries a sheet rubber gasket 29 
communicated to ambient atmosphere by vent opening 21. 
The mold is embedded in particulate mass 26 selected to exhibit low 
reactivity to the particular reactive alloy being melted and cast into the 
mold 22 so that in the event of any melt leakage from the mold 22, the 
melt will be confined in a manner without harmful reaction in the mass 26. 
Suitable particulates for a representative TiAl melt comprise mullite or 
zircona grain from -20 to +50 mesh size. The particulates can be selected 
from other materials as desired in dependence on the reactive alloy to be 
melted. 
The rubber gasket 29 compacts the particulate mass 26 about the mold 22 
when a relative vacuum is drawn in the container 20 so that the mold 22 is 
exteriorly supported during casting as it is filled with molten alloy. 
The mold container 20 includes a peripherally extending chamber 36 
communicated via a conventional on/off valve 38 to a source 40 of vacuum, 
such as a vacuum pump. The chamber 36 is screened by a perforated screen 
41 selected to be impermeable to the particulates of mass 26 so as to 
confine them within the container 20. The mold container 20 also includes 
an inlet conduit 37 for admitting argon or other inert gas from a suitably 
screened distribution conduit 43 to the container from a suitable inert 
gas source 47. The mold section 10 can be of the type described and shown 
in detail in aforementioned U.S. Pat. No. 5,299,619. 
The melting section 12 includes a metal (e.g. steel) melting enclosure 50 
forming a melting chamber 52 about a refractory melting vessel or crucible 
54. The melting enclosure 50 includes a side wall 56 and a removable top 
58 sealed to the side wall via a sealing gasket 60. A sliding cover 61 of 
the type set forth in aforementioned U.S. Pat. No. 5,042,561 is disposed 
on a fixed cover 59 of the top 58 and is slidable to receive fill pipe 23 
for the purposes set forth in the patent. The fixed cover 59 includes an 
opening 59a for the mold fill pipe 23. The sliding cover 61 includes a 
opening 61a for receiving fill pipe 23 when openings 59a, 61a are aligned 
to countergravity cast the melt from the vessel 54 into the mold 22. 
Pursuant to an apparatus embodiment of the invention, a hollow water-cooled 
induction coil 68 is provided about the melting vessel 54. The induction 
coil 68 includes a selectively energizable segment 68a encompassing the 
upper region of the melting vessel 54 and a lower segment 68b integral 
with the first upper segment 68a and encompassing a lower region of the 
melting vessel. Preferably, the upper segment 68a encompasses about 1/3 of 
melting vessel 54; i.e. the uppermost 1/3 region of the melting vessel. 
The segment 68b encompasses much of the remaining 2/3 region of melting 
vessel. 
Alternately, the invention can be practiced using a separate upper 
induction coil corresponding to hollow water cooled coil segment 68a and a 
separate hollow water cooled induction coil corresponding to lower coil 
segment 68b. Each of the upper coil and separate lower coil would have two 
electrical leads corresponding to leads L to the power source S so that 
the upper coil could be energized selectively for preheating charge 
component C2 and both the upper and lower coils could be energized to melt 
the charge components C1, C2 as described below. 
The side wall 56 includes a sealed entry port 66 for passage of electrical 
power supply lead wires L connecting couplings 69a, 69b, 69c to electrical 
power source S via switch SW. The power source can comprise a conventional 
solid state frequency converter, although the invention is not limited to 
any particular power source. Electrical couplings 69a, 69c are connected 
to opposite ends of the upper coil segment 68a to provide means for 
electrically energizing the upper segment 68a, while couplings 69a, 69b 
are connected to opposite ends of the upper and lower segments 68a, 68b to 
provide means for electrically energizing the entire coil 68; i.e. both 
upper and lower segments 68a, 68b. A switch SW associated with the power 
source S is connected as shown in FIGS. 1 and 2 so that the electrical 
couplings 69a and 69c can be energized by the power source S to 
selectively energize the upper coil segment 68a and also so that 
electrical couplings 69a and 69b can be energized by the power source S to 
energize the entire coil 68. Electrical coupling 69b is connected to the 
coil 68 above its bottom turns so that the bottom turns can provide 
structural support of the crucible and keep power leads from metal support 
flanges 84, 84b. 
The side wall 56 also includes a port 70 communicated via a conduit 72 and 
valve 74 to a source 76 of argon or other inert gas and, alternately, to a 
vacuum source (e.g. vacuum pump) 78. 
The side wall 56 further includes an annular shoulder or flange 84 on which 
multiple coil supports 86 are circumferentially spaced and sit to support 
the induction coil 68. The flange includes an outer annular shoulder or 
flange 84a fastened to inner annular shoulder or flange 84b on which coil 
supports are disposed to support the induction coil 68. A mass 119 of low 
reactivity particulates, such as 100 mesh zirconia powder, extends 
upwardly between the coil 68 and the melting vessel 54 so as to confine 
any melt that might leak or otherwise escape from the vessel 54 within the 
low reactivity particulates. 
The melting vessel or crucible 54 comprises a cylindrical tubular ceramic 
shell 90 having bottom 90a, which may be integral with the tubular 
crucible section or a separate component bonded to the tubular crucible 
section. For casting titanium based melts, the crucible 54 comprises 
zirconia faced mullite ceramic. 
For casting titanium based melts, the mold 22 comprises an inner zirconia 
or yttria facecoat and zirconia or alumina outer backup layers forming the 
body of the mold (e.g. see U.S. Pat. No. 4,740,246). The total mold wall 
thickness can be from 0.1 to 0.3 inch. The inner facecoat is selected to 
exhibit at most, only minor reaction with the titanium based melt cast 
therein so as to minimize contamination of the melt. A preferred mold 
facecoat for casting titanium based melts is applied to a fugitive mold 
pattern as a slurry comprising zirconium acetate liquid and zirconia 
flour, dried, and stuccoed with fused alumina (mesh size 80). One facecoat 
layer typically is applied. Preferably, backup layers for use with this 
facecoat are applied as a slurry comprising ethyl silicate liquid and 
tabular alumina, dried, and stuccoed with fused alumina (mesh size 36). 
The open upper end of the melting vessel 54 may be partially closed by a 
closure plate 100 made of fibrous alumnia. The plate 100 includes central 
opening 102 through which the fill pipe 23 can be extended as shown in 
FIG. 2. 
The lower closed end of the melting vessel 54 may include an outer shoulder 
or flange 110 that sealingly engages a similar shoulder or flange 120, 
which supports access port cover or closure 122. 
For purposes of further illustrating a method embodiment of the invention 
to melt a Ti-6Al-4V alloy, a lower (underlying) solid charge component C1 
of elemental titanium solid pieces (shown as slivers) and elemental 
vanadium solid pieces (shown as solid black chunks) interspersed together 
are positioned as the solid charge component (comprising about 2/3 of the 
total charge height in the melting vessel) in the lower region of the 
melting vessel 54 as illustrated, for example, in FIG. 1. The lower charge 
component C1 itself can be stratified or layered to include elemental 
titanium pieces proximate the bottom of the melting vessel 54 to comprise 
about one-half of the charge component C1 and a mixture of elemental 
titanium solid pieces and dispersed elemental vanadium solid pieces 
positioned to overlie the lower titanium pieces to comprise the remaining 
one-half of the charge component C1. The titanium pieces and vanadium 
pieces can be mixed together prior to introduction to the melting vessel 
54 or can be mixed as or after they are introduced to the melting vessel. 
Alternately, prealloyed titanium-vanadium alloy pieces can be introduced 
to the 2/3 of the melting vessel where charge C1 resides. The titanium and 
vanadium pieces have respective melting points of 3035 degrees F. and 3450 
degrees F., thereby constituting the higher melting point components of 
the total charge to be melted as compared, for example, to the remaining 
aluminum charge component having a melting point of 1220 degrees F. 
In addition to or in lieu of vanadium, the titanium pieces may be 
interspersed with pieces of other metals such as molybdenum, chromium, 
niobium, silicon and others, which are present in some titanium alloys. 
Niobium typically is present in the form of a master alloy of, for 
example, niobium and aluminum as a result of difficulty in melting niobium 
due to its very high melting point. These other metals (e.g. molybdenum, 
chromium, niobium, silicon and others) typically would be dispersed with 
titanium pieces in a stratified or layered charge component C1 where 
elemental titanium pieces are placed proximate the bottom of the melting 
vessel to comprise about one-half of the charge component C1 and a mixture 
of elemental titanium solid pieces and pieces of these other metals are 
positioned over the lower titanium pieces to comprise the remaining 
one-half of the charge component C1. Although a predominant amount of the 
other metal pieces are dispersed with the titanium pieces in the 
stratified charge component C1 as described, some minor amount of the 
other metal pieces may be dispersed in the upper charge component C2 as 
the melting vessel 54 is charged. 
After the aforementioned lower solid charge component C1 comprising 
titanium interspersed with some vanadium or other metals as described 
above is introduced into the melting vessel, the lower melting point upper 
charge component C2 comprising solid aluminum pieces (shown as round shot 
or particles) and titanium pieces are introduced into the top 1/3 of 
melting vessel 54 in upper region of the melting vessel so as to overlie 
the higher melting point solid charge component C1 (e.g. titanium and 
vanadium pieces). The aluminum pieces of charge component C2 may be 
charged with titanium pieces to disperse the aluminum pieces for 
preheating and improve reactivity of melted aluminum with the titanium 
pieces present. 
The charge component C1 may include aluminum interpersed with a lower 
melting point metal (e.g. tin) used in some titanium alloys (e.g. 
Ti-5Al-2.5 Sn alloy). 
The solid titanium pieces can comprise titanium scrap sheet, briquettes, 
niblets or other shapes. The titanium scrap sheets are typically 1 inch by 
1 inch by 1/16 inch in size and obtained from Chemalloy Co. The briquettes 
are made of titanium sponge to sizes approximately 1 inch by 1 inch by 3 
inches. The titanium charge component is added in an amount to provide the 
desired Ti weight % in the alloy melt. 
The vanadium source can comprise vanadium or vanadium-aluminum alloy shot, 
scrap sheet, or other shapes. For example, vanadium-aluminum alloy 
typically is provided in the form of -8 to +50 mesh grains. The vanadium 
charge component is added in an amount to provide the desired V weight % 
in the alloy melt. 
The solid aluminum pieces can comprise aluminum scrap sheet, shot, or other 
shapes. For example, aluminum typically is provided in the form of 1/4 
inch diameter shot. The aluminum charge component is added in an amount to 
provide the desired Al weight % in the alloy melt. 
For charging, the melting vessel 54 is assembled and supported on cover 
122. The melting vessel 54 with the plate 102 removed is charged manually 
with the solid charge components C1, C2 as described above. The charged 
melting vessel 54 is placed within the induction coil 68 as shown in FIG. 
2 with the cover or closure 122 sealed against enclosure 50 and with 
removable top 58 removed from the enclosure 50. The particulates 119 (e.g. 
zirconia grain) then are placed about the melting vessel 54 as shown in 
FIG. 2 through open enclosure 50. After the particulates 119 have been 
added and plate 102 repositioned on the melting vessel 54, the top 58 is 
sealed back on enclosure 50. 
At the beginning of the melting/casting cycle for Ti based melt, the 
melting chamber 52 is first evacuated to less than 0.2 torr (200 microns) 
and then is backfilled with argon to slightly above atmospheric pressure 
(controlled to as much as 1 torr pressure) via the port 70. 
Then, in accordance with an embodiment of the invention, the coil segment 
68a (or separate upper coil) is selectively energized via electrical leads 
L by coupling 69a, 69c and the power source S to selectively inductively 
preheat the upper charge component C2 (e.g. mostly aluminum and titanium 
pieces) in the melting vessel 54 to an increased temperature above the 
temperature of the first charge component C1. Typically, the upper charge 
component C2 is selectively induction preheated to an increased 
temperature determined by the alloy being melted and cast. If multiple 
charge components are present in the upper melting charge component C2, 
all components are heated and/or melted in accordance with their physical 
properties (e.g. melting points). The selective induction preheating of 
the upper charge component C2 increases the temperature thereof and 
thereby increases the resistivity of the charge component C2. The higher 
melting point charge component C1 at the lower region of the melting 
vessel 54 is only minimally heated by energization of coil segment 68a so 
that its temperature remains near ambient temperature in the bottom of the 
melting vessel 54. 
For purposes of illustration only, a charge component C2 comprising 1.7 
pounds of aluminum and 7.3 pounds of titanium can be selectively induction 
preheated at a power level of 180 to 200 kilowatts by energizing coil 
segment 68a for a time of 7 to 7.5 minutes. The temperature of the upper 
charge component C2 thereby is raised to about 1500 to about 1750 degrees 
F., which is above the melting point of aluminum of 1220 degrees F. and 
below the melting point of titanium of 3035 degrees F. 
After selective induction preheating of the second charge component C2, 
both the preheated second metal charge component C2 at the upper region of 
the melting vessel 54 and the first charge component C1 at the lower 
region of the melting vessel are induction heated and melted by energizing 
the entire induction coil 68 including segments 68a, 68b (or separate 
upper/lower coils) via electrical leads L by coupling 69a, 69b at a much 
higher power level. Since the upper charge component C2 exhibits a higher 
resistivity as a result of being selectively induction preheated to the 
increased (superambient) temperature and thus generates more heat upon 
induction heating at the higher power input, the upper charge component C2 
(including mostly the aluminum and titanium pieces) thus melts first and 
flows toward the bottom of the melting vessel 54. As top-to-bottom melting 
of the charge components C2, C1 occurs, the molten alloy thereby formed is 
substantially held away from the side walls of the vessel 54 by the high 
induction power level so as to reduce adverse reaction between the molten 
alloy and the vessel refractory material. Moreover, the bottom center of 
the higher melting point charge component C1 is the last region of the 
charge to melt and reduces adverse reaction of the molten alloy with the 
refractory material at the bottom of the vessel 54. 
For purposes of illustration only, a lower charge component C1 comprising 
17.7 pounds of titanium and 1.7 pounds of vandium and upper charge 
component C2 comprising 1.7 pounds of aluminum and 7.3 pounds of titanium 
can be induction heated and melted at a power level of 220 to 300 
kilowatts by energizing both coil segments 68a, 68b via couplings 69a, 69b 
for a time of 130 to 220 seconds. The high induction power level is 
effective to substantially hold the molten TiAl alloy thereby formed away 
from the side walls of the melting vessel 54 as top-to-bottom melting of 
the charge components proceeds so as to reduce adverse reaction between 
the molten alloy and the vessel refractory material. 
As soon as the melt reaches the desired casting (superheat) temperature 
(e.g. about 3100 degrees F. after only about 3 minutes for a Ti-6Al-4V 
melt), the container 20 already filled with an inert gas, such as argon, 
through inlet 37 is lowered to insert the fill pipe 23 through the port 
59a and also port 102 into the melt M in the vessel 54, FIG. 2. The 
container 20 is moved by the aforementioned hydraulically actuated arm 
(not shown). Before or upon immersion of the fill pipe 23 in the melt, a 
vacuum is drawn in the container 20 via chamber 36. A vacuum thereby is 
applied to the mold 22 compared to atmospheric argon gas pressure in the 
melting chamber 52 so as to establish a negative pressure differential 
between the mold cavities 24 and the melt in the vessel 54 sufficient to 
draw the melt upwardly through the fill pipe 23 into the mold 22. 
The melt-filled mold 22 (just removed from the melting chamber 52) is left 
in its container 20 and argon flow is provided through inlet 37 so that 
the melt can solidify and/or cool under argon gas to a lower temperature 
of, for example only, 800 degrees F. before the mold 22 is removed from 
the container 20. The following Examples are offered for purposes of 
further illustrating, and not limiting, the invention. 
EXAMPLE 1 
melting of TiAl melt: 
A crucible refractory lining material comprising zirconia faced mullite was 
used. The charge was melted in an argon atmosphere. The lower charge 
component C1 comprised of 27 pounds of Ti in niblet form (nibled flake 
shaped pieces) and the upper charge component C2 comprised 15 pounds of Al 
in shot form mixed with some titanium niblets. The inital power input to 
an upper induction coil 68a to heat charge component C2 was 190 kilowatts 
applied for 7 minutes. Then, full power input to upper and lower induction 
coils 68a, 68b was applied at 200 kilowatts for 100 seconds to heat and 
melt charge components C1 and C2 to achieve melt temperature of about 2900 
degrees F. The total time to melt C1 and C2 was 520 seconds. The melt was 
countergravity cast at vacuum of 18 inches Hg in mold container into 28 
mold cavities in mold having zirconia facecoat with mold embedded in 
mullite particulates and using a steel fill tube. 
EXAMPLE 2 
melting of Ti-6Al-4V melt: 
A crucible refractory lining material of zirconia faced mullite was used. 
The charge was melted in an argon atmosphere. The lower charge component 
C1 comprised 25 pounds of Ti in niblet form and 1.1 pounds of vanadium in 
shot form. The upper charge component C2 comprised 1.7 pounds of Al in 
shot form mixed with some titanium niblets. The inital power input to an 
upper induction coil 68a to heat Al charge component was 190 kilowatts for 
7.5 minutes. Then, full power input to upper and lower induction coils 
68a, 68b was applied at 260 kilowatts for 172 seconds to heat and melt 
charges C1 and C2 to achieve melt temperature of about 3100 degrees F. The 
total time to melt charges C1 and C2 was 622 seconds. The melt was 
countergravity cast at vacuum of 29 inches Hg in mold container into 20 
mold cavities in mold having zirconia facecoat with mold embedded in 
mullite particulates and using a steel fill pipe. 
Although the invention has been shown and described with respect to certain 
embodiments thereof, it should be understood by those skilled in the art 
that other various changes, modifications, and omissions in the form and 
detail thereof may be made therein without departing from the spirit and 
scope of the invention as set forth in the appended claims.