The design and some construction details of two laboratory vacuum furnaces for casting metals

MISSING IMAGE

Material Information

Title:
The design and some construction details of two laboratory vacuum furnaces for casting metals
Series Title:
United States. Atomic Energy Commission. MDDC ;
Physical Description:
13 p. : ill. ; 27 cm.
Language:
English
Creator:
Selmanoff, Eugene D
Los Alamos Scientific Laboratory
U.S. Atomic Energy Commission
Publisher:
Technical Information Division, Atomic Energy Commission
Place of Publication:
Oak Ridge, Tenn
Publication Date:

Subjects

Subjects / Keywords:
Metallurgy   ( lcsh )
Metal castings   ( lcsh )
Metallurgical furnaces   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 13).
Restriction:
"Date Declassified: February 20, 1947."
Statement of Responsibility:
by Eugene D. Selmanoff.
General Note:
Manhattan District Declassified Code.
General Note:
"Date of Manuscript: June 29, 1946."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 005023789
oclc - 277770487
System ID:
AA00009324:00001


This item is only available as the following downloads:


Full Text
r Y.' /a 6




MDDC 1126
(LADC 279)



UNITED STATES ATOMIC ENERGY COMMISSION








THE DESIGN AND SOME CONSTRUCTION DETAILS OF TWO
LABORATORY VACUUM FURNACES FOR CASTING METALS



by
Eugene D. Selmanoff





Los Alamos Scientific Laboratory


Aprg 4.'


Date of Manuscript:
Date Declassified:


June 29, 1946
February 20, 1947


Issuance of this document does not constitute
authority for declassification of classified
copies of the same or similar content and title
and by the same author.




Technical Information Branch, Oak Ridge, Tennessee
AEC, Oak Ridge, Tenn., 4-20-49--850-A1320


Printed in U.S.A.
PRICE 10 CENTS













































*r




































~i




ai
















THE DESIGN AND SOME CONSTRUCTION DETAILS OF TWO
LABORATORY VACUUM FURNACES FOR CASTING METALS


By Eugene D. Selmanoff


ABSTRACT

The designs of two laboratory furnaces for vacuum casting metals are described in detail. The
first furnace employs a tungsten or molybdenum resistance winding. The furnace is constructed in two
parts, an upper brass cylindrical "can" containing the heating coil, resting on a similar lower can in
which the mold is placed. Bottom pouring technique is employed in both furnaces. The second furnace
uses high frequency induction heating, but may be adapted for resistance heating. It consists of an
open-end silica tube resting on a brass cylindrical can. The induction coil fits around the silica tube
and the crucible stands inside the tube. The mold is accommodated by the brass can. In both furnaces
temperatures in the neighborhood of 1500 degrees C at pressures of 10-3 to 10-5 mm Hg have been
obtained. The design of a vacuum gate valve, compression gland are also given.






Techniques for vacuum casting metals, both in the laboratory and in industry, have been greatly
improved and developed during the war period. New furnace designs and methods of construction
should be of considerable interest to the metallurgist and others concerned with the problem of casting
metals in vacuum. This is especially true in view of the scarcity of metallurgical or other scientific
literature in this field.
Furnaces for melting or casting metals may be divided into two groups, (1) glass systems, and
(2) metal systems. The former similar in construction to the glass systems commonly used in
chemical and physical laboratories for carrying out reactions or experiments in vacuum. The ma-
jority of the parts and connections are usually made by the fusion of the glass or by the use of ground
glass joints of one type or another. Such a system, as far as melting of metals is concerned, is
usually limited to small melts, from less than 1 g to several hundred grams. A strict upper limit
cannot be set. For melts of greater size and especially where casting is required it is desirable to
go to metal systems primarily because of their greater mechanical strength and ease of construction
when dealing with large parts. In these systems the majority of the parts are metal, usually brass,
copper or steel, and the various components of the system are connected by soft or hard-soldering,
welding, or bolting. The furnaces discussed in this paper are parts of metal systems.

LITERATURE ON VACUUM CASTING

The writer could find no literature on furnaces designed for vacuum casting. However some litera-
ture is available on the design of vacuum melting furnaces. The Arsem' vacuum furnace is probably
the most widely known of this type. It employs a helical graphite coil as an electrical resistance unit
and the vacuum is produced within a cylindrical gun-metal casting. Temperatures of 3100 degrees C
were obtained in the original furnaces constructed by Arsem.


MDDC 1126








MDDC 1126


List of Parts for Figure 1.


Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34


Material
Brass or steel
Rubber
Brass
Brass
Brass
Glass
Rubber
Brass
Brass
Copper
Steel
Brass
Brass
Stainless steel
Stainless steel
Brass or copper
Copper
Suitable refactory
Steel
Brass
Rubber
Brass
Brass
Brass or copper
Brass
Brass
Copper
Suitable refractory
Suitable refractory
Steel
Alundum
Alundum-60 mesh
Alundum
Tungsten or
molybdenum
Suitable refractory
Sil-o-Cell
Suitable material
Steel
Copper


Part (nonimal dimensions in inches)

3/8-16 x 1-1/4 Hex head screw
1/8 x 1/8 Gasket
8 Diam x 1/2 Top plate
8-32 x 1/2 Filister head screw
Window cover plate
1 Diam x 1/8 Pyrex window
1/8 x 1/8 Gasket
1/4 Diam Pouring rod extension
1/4 Wilson seal
1/4 OD Cooling water coil
6-13/16 OD x 6-11/16 ID x 1/4 Split ring
8 OD x 6-3/4 ID x 1/2 Ring
3/8 x 3/8 x 1-3/4 Bar
Pouring rod extension, 1/4 Diam
Pouring rod coupling
6-3/4 OD x 6-1/2 ID x 10 Furnace can
1/4 OD Cooling water coil
3/8 Diam Pouring rod
6-1/2 OD Furnace support
8 OD x 6-3/4 ID x 1/2 Ring
1/4 x 1/4 Gasket
8 OD x 6-3/4 ID x 1/2 Ring
1/4 Compression gland
6-3/4 x 6-1/2 x 6 Mold can
8 Diam x 1/2 Bottom plate
Flange, See Figure 2-11
Water-cooled lead
1/4 Coverplate
1/4 Crucible cover
5 OD x 4-15/16 ID x 5-1/4 Coil can
Insulating tube
Insulation
3-3/4 OD x 3-1/4 ID x 4-1/4 Coil tube
30 mil wire

Crucible
Insulation
Mold
5 Diam x 1-1/4 Mold stool
1/4 OD Cooling water coil









MDDC 1126


CROSS-SECTION THROUGH CENTER


Figure 1. Resistance heated vacuum casting furnace.








MDDC 1126


W. F. Ehret and David Gurinskya have described a carbon tube resistance furnace which they
claim has the advantages of low cost, compactness, and rapid heating. The metal vacuum can is
roughly 7 inches in diameter by 7 inches in height and operates in the pressure range 10-3 to 10-5
mm Hg or with a special atmosphere. Twenty- five g melts have been made at 1550 degrees C in 6
minutes, and charges up to 100 g can be used.
Two vacuum distillation furnaces which are suitable for melting and employing high-frequency
induction heating have been described by J. B. Friauf.9 In these furnaces, the vacuum is produced
within a fused quartz tube around which the induction coil fits. In one furnace, the silica tube is 4
inches inside diameter and 2 feet long; and in the other, it is 6 inches inside diameter and 30 inches
long. The furnaces differ principally only in size. The upper end of the silica tube is sealed to a
brass ring which has a side tube leading to the vacuum pumps. The vacuum connection at the top of
the quartz tube has some advantage over one at the bottom of the furnace, because it allows the entire
furnace to be placed at a lower, more convenient location.
F. M. Walters12 has described a high-frequency induction furnace used for melting under a con-
trolled atmosphere (argon). It consists of a fused quartz tube 10 inches in diameter and 24 inches
long, closed at the bottom by a water cooled brass casting, and at the top by a brass ring and water
cooled cover. The high-frequency coil is placed inside the quartz tube, three leads passing through
one inch holes drilled in the quartz tube. Melts of 2-5 Ibs. were made in this furnace.
Methods and applications of melting and evaporating metals in vacuum have been discussed by
Kroll."o The paper mentions several more unusual methods of vacuum melting, such as an arc furnace,
and the Hultgren'oelectron-bombardment furnace.
This article will describe the design and some details of construction of two laboratory furnaces
designed for vacuum casting, one employing resistance heating and the other employing induction or
resistance heating. The reader desiring merely a melting furnace can easily simplify the designs
given to meet this single function. In addition some accessory metal vacuum system equipment will
be described.


A RESISTANCE-HEATED FURNACE

A furnace designed for resistance heating is shown in Figure 1. The furnace is composed of two
parts, the upper "can"* (16) which contains the heating coil, and the lower can .(24) which contains the
mold. The advantage of this type of construction is that the heating coil, which tends to become quite
fragile with use, is not disturbed (as would probably be the case if the entire furnace were in one part)
when the mold is placed in, or removed from the furnace.
The design and method of construction can be seen by an examination of Figure 1 and Figure 1-
List of Parts. In the List of Parts, some of the dimensions are given only nominally, and some were
omitted if they were of little importance.

Upper Can
The upper furnace can, which may be made of either brass or copper, is 6 3/4 inches in diameter
and 10 inches high. It is cooled by water flowing through several turns of 1,4 inch diameter copper
refrigerator tubing (17). The turns are spaced 1 inch or slightly more apart and are soft-soldered to
the can. The can is closed at its upper end by a brass plate (3) bolted to the can by six machine
screws (1) and a ring arrangement (11, 12).



The figures in parentheses in this section refer to parts shown in Figure 1, unless otherwise
indicated.









MDDC 1126


The plate has a Pyrex window (6), a sliding (or Wilson) seal (9) for introduction of translator
motion into the vacuum, ana is water cooled (10). The window shown is 1 inch in diameter, but in
general a larger window facilitates visual and pyrometric observations of the melts. Suitable Pyrex
windows of various dimensions may be obtained from the Corning Glass Works. A window shutter
(not shown) has been found effective in preventing or decreasing fogging of the window due to con-
densation of volatile constituents from the melts. Such a shutter may be fashioned from a 20 gauge
piece of sheet steel, roughly teardrop i shape and pivoted at the narrow end by a screw threaded to
the underside of the top plate. The shutter can be opened and closed by sliding an Alnico magnet in
the desired direction along the topside of the plate. The construction and dimension of the Wilson
seal have been thoroughly described by Wilson.17 It is probably desirable, where possible, to inter-
change the position of the Wilson seal and the window as shown in Figure 1, because an off-center
window usually provides a better view of the melt.
It is necessary to have some play in the pouring rod connections to compensate for the small
misalignments of the crucible or the whole heating coil assembly that usually occur. A sloppy fit
where extension (14) is threaded into coupling (15) has usually been sufficient. The pouring rod (18)
fits into a hole in the coupling and is secured by an Allen head screw. When the crucible is loaded
the pouring rod together with the coupling (15) and extension (14) is placed in position. After the
crucible is lowered into the furnace, extension (14) fits into a hole in arm (13) and is fastened with
a thumbscrew. This operation is performed as the top plate is held in a horizontal position several
inches above the can.
The rubber gaskets (2, 7, 21) can be obtained, in various cross sections, by the foot. Circular
cross section gaskets can also be used.
The heating coil consists of 30 mil tungsten or molybdenum wire inside wound on a 3 1/4 inch
inside diameter alundum tube. It was not possible to purchase inside-threaded tubes so the threads
were ground by an abrasive wheel; six threads per inch, approximately 1/3 inch deep. Tungsten wire
is easier to wind than molybdenum, due to the greater stiffness of the tungsten. The two ends of the
coil winding are fastened to 50-60 mil molybdenum wire which is run to the water-cooled leads (27).
Several methods of fastening two pieces of resistance wire together have been used successfully. The
two pieces may be placed alongside and running parallel to each other and be tied together with 1-2 mil
molybdenum wire. Another method is to run a single loop of 20-30 mil molybdenum wire around the
two pieces, placed in any position, and tightening the loop by twisting its ends together. The heating
coil unit rests on a steel ring (19) which in turn rests on three pins (not shown) fastened to the wall of
the can. Heat loss by radiation may be reduced by introducing one or more metal shields between the
heating coil assembly and the can.

Water-Cooled Leads
The construction of the water cooled leads is shown in Figure 2. The brass flange* (11) is soft-
soldered to the back of the upper can (Figure 1-26). An insulating plate (7) is screwed to the flange and
the two leads protrude through and are secured to this plate. The drawing does not show the small hole
through the extreme right end of (8) through which the furnace lead passes and is held by an Allen
head screw. An electrical input wire is fastened to a hose clamp which is clamped on the excess
threaded portion of (8) next to nut (4). The water inlet and outlet t1, 2) are soft-soldered to disc (3)
which is soft-soldered to (8). Two or three 3 inch diameter sheet metal radiation shields are placed
in front of the insulating plate to protect it from direct radiation. Pyrex tubes are slipped over the ends
of the leads to prevent contact and subsequent electrical shorting by the shields.


SThe figures in parentheses in this section refer to parts shown in Figure 2, unless otherwise
indicated.









MDDC 1126


CROSS-SECTION THROUGH CENTER


Figure 2. Construction of water-cooled leids.
Figure 2-List of Parts
Material Part (nominal dimensions in inches)


Copper tubing
Copper tubing
Copper
Brass
Brass
Rubber
Micarta
Copper
Brass
Rubber
Brass
Brass or Copper


1/8 OD hard drawn, Water inlet
1/8 OD hard drawn, Water outlet
1/2 Diam x 3/16 End piece
3/4 16 Hex head nut
1 OD x 3/4 ID x 1/4 Washer
1 OD x 3/4 ID x 1/4 Gasket
4-3/4 Diam x 1/2 Insulating Plate
Lead Body
Filister head screw
1/8 x 1/8 Gasket
4-3/4 OD x 3 ID x 1/8 Wall x 3-1/4 Flange
Furnace can wall


CROSS SECTION THROUGH CENTER


Figure 3. 1/4 inch compression gland.
Figure 3-List of Parts
:erial Part (nominal dimensions in inches)

Lss Hex head screw
iss Body
Lss Washer
)ber Gasket


Number

1
2
3
4
5
6
7
8
9
10
11
12


Number
1
2
3
4


Mat
Bra
Bra
Bra
Rut









MDDC 1126


Lower Can
The upper can rests on the lower (mold) can. A vacuum tight seal is provided by the gasket (21).
It should be noted that this gasket is protected from direct radiation of heat by a slight projection of
the upper can (B). It is important that no rubber gaskets in the system be subjected to direct radia-
tion. The rings (20, 22) are hard-soldered to their respective cans (A).
Four 1/4 inch compression glands (23 and Figure 3) are soft-soldered roughly 45 degrees apart
around the back side of the can. They are used for the introduction of vacuum gages, thermocouple
wires, electrical connections to a mold heating coil, etc., into the system. A convenient method of
interchanging vacuum gage tubes in the system is to fuse the female part of a semiball joint to each
tube. By means of an L-shaped glass tubing having a stopcock, the male part of a semiball joint on
one end, and the other end in the compression gland, tubes may be changed during a run without
breaking the vacuum.
The bottom plate is secured to the lower can in the same way that the top plate is secured to the
upper can. The bottom plate has a 4 inch diameter vacuum outlet and a 1/2 inch diameter hole for
connection to a roughing system. It is also water cooled (39). The mold (37) which rests on a short
metal stool (38) can be raised if it is desired to shorten the distance through which the metal drops
from crucible to mold.

Furnace Support
A method of supporting the entire furnace has not been shown. Four 3/8 inch diameter steel rods
are threaded into the bottom of a steel ring similar in cross section to (19). The rods are then bolted to
a table top and the furnace is placed on the ring. Sufficient distance is allowed between the ring and the
table top for insertion of a gate valve (Figure 5) which is bolted on to the bottom plate (25).


AN INDUCTION OR RESISTANCE-HEATED FURNACE

A furnace that was originally designed for induction heating, but which may easily be adapted for
resistance heating, is shown in Figure 4. The lower can is very similar in design to the lower can
shown in Figure 2. The crucible is placed within a fused quartz tube* (13) which rests on the top plate
(17) and around which the induction coil (not shown) fits. The tube shown is 3 1/2 inches in outside di-
ameter by 3 inches in inside diameter by 15 inches in height. A tube of this length allows one to place
both the crucible and mold within the quartz tube, provided the diameter of the mold is small enough
to fit. The crucible may then rest directly on the mold, if desired, thereby eliminating the long metal
drop which is unavoidable when the crucible and mold are in the positions shown in Figure 4. It is
always desirable to have the outside diameter of the tubes as small as possible because increasingly
greater magnetic coupling as obtained as the diameter of the induction coil approaches the diameter of
the crucible. On the other hand, the tube should be large enough to permit the use of radiation shields,
and to allow free passageway for gases past the crucible to the vacuum outlet. The design shown in
Figure 4 is useful because it permits the use of a mold which has too large a diameter to fit inside of the
quartz tube.
Fused quartz tubes having either a sand cast surface or a mold surface (both have been used satis-
factorily) may be obtained from Thermal Syndicate Ltd., New York, or Amersil Co., Inc., Hillside, New
Jersey. Tubes supplied by the former have had less variation in the dimensions of the inner and outer
diameter. Vycor (Corning Glass Works) and Pyrex tubes have also been used satisfactorily, although
they have thinner walls and are more easily damaged by mechanical shock. It is desirable to have a
radiation shield (24, 26) around the crucible (27). Refractory or metal shields may be used. Metal shields
must be slotted to prevent heating by induction.

The figures in parentheses in this section refer to parts shown in Figure 4, unless otherwise
indicated.









MDDC 1126


List of Parts for Figure 4


Number

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35


Material

Brass
Brass
Brass
Glass
Rubber
Brass
Brass
Copper
Brass
Stainless Steel
Stainless Steel
Suitable refractory
Fused quartz
Suitable refractory
Rubber
Copper
Brass
Steel
Brass
Copper
Brass or Copper
Brass
Rubber
Suitable refractory
Suitable refractory
Suitable refractory
Suitable refractory
Suitable refractory
Suitable refractory
Brass
Rubber
Brass
Suitable material
Steel
Copper


Part (nominal dimensions in inches)

4-1/2 Diam x 1/2 Top plate
8-32 x 1/2 Filister head screw
Window cover plate
1 Diam x 1/8 Pyrex window
1,'8 x 1 8 Gasket
1,,4 Diam Pouring rod extension
1/4 Wilson seal
1 '4 Diam Cooling water coil
3/8 x 3/8x Bar
Pouring rod extension, 1/4 Diam
Pouring rod coupling
5 16 Diam Pouring rod
3-1,2 OD x 3 ID x 15 Tube
Crucible support
3-1 2 OD x 3 ID x 1/8 Gasket
1/4 Diam Cooling water coil
8 OD x 2-1/2 ID x 1/2 Top plate
6-13/16 OD x 6-11/16 ID x 1'4 Split ring
8 OD x 6-3/4 ID x 1/2 Ring
1.'4 OD Cooling water coil
6-3/4 OD x 6-1, 2 ID x 6 Mold can
8 OD x 4 ID x 1/2 Bottom plate
3-1 2 OD x 3ID x 1/8 Gasket
2-3/4 Diam x 3/16 Radiation shield
2 Diam x 3/16 Crucible cover
2-3/4 OD Radiation shield
2 OD Crucible
2-3/4 Diam Insulating plate
2-3/4 Diam Insulating plate
3/8-16 x 1-1/4 Hex head screw
1/8 x 1/8 Gasket
1/4 Compression gland
Mold
5 Diam Mold stool
1/4 Cooling water coil









MDDC 1126


CROSS-SECTION THROUGH CENTER

Figure 4. Induction or resistance heated vacuum casting furnace.









MDDC 1126


It will be noted that the quartz tube is not fastened to the plates at either end. Vacuum tight
seals are obtained by the use of atmospheric pressure. Top and bottom plates may be secured to the
quartz tube by means of a ring arrangement similar to that used on the brass lower can,* but this
arrangement has been found to be unnecessary.
The cooling coil (16) may be eliminated by turning a groove in plate (17) and soft soldering an
annular copper ring on top of the groove. This change will permit the induction coil to be lowered
slightly without arcing the top plate. Other design features of the lower can may be obtained from
the description of Figure 1. The entire furnace is supported in the same way as the resistance-
heated furnace.

Adaption for Resistance Heating.
The lower mold can in Figure 4 may be used "as is" to support an upper can containing a re-
sistance heating coil. The upper can is identical in design to that shown in Figure 1 with the excep-
tion of the bottom ring (Figure 1-20) which is modified to fit on to the top plate (Figure 4-17).


A VACUUM GATE VALVE

A relatively simple design of a vacuum gate valve is shown in Figure 5. The principal feature
of this design is that it allows an unobstructed and unrestricted flow of gas from furnace to pumps
when the valve is in the open position. The valve is shown in the closed position.
The principal parts of the valve are a guide plate (10) which slides in a horizontal direction in
the valve housing (3, 8, 9), the upper and lower gates (12), and a cam (11) actuated by the rod (4).
The guide plate slides in 1/8 inch deep grooves cut in the two side walls (not shown) of the
housing. When in the closed position, the guide plate is at the extreme right hand end of the housing.
Four guide pins (15) are fastened (force fit) in the guide plate to direct the vertical motion of the
upper and lower gates. The pressure exerted by the cam on the gates (the position shown in Figure 5)
is released when the handle (14) is turned 90 degrees. Both gates are then pulled toward the guide
plate by the action of coil springs (16) which fit over the guide pins and are fastened to the gates
and to the guide plate (the upper gate is assisted by the force of gravity). The handle is then pulled
to the right and the entire internal assembly is removed from the position shown leaving a straight
unobstructed passageway for the gas molecules.
The upper flange (1) is bolted to the furnace bottom plate and the lower flange is bolted to the
desired part of the vacuum system.
The parts of the valve housing are screwed together (using flat head screws) and all seams and
screw holes are soft soldered. It is usually advisable to paint over the soldered seams withcolorless
Glyptal (General Electric Co.).
If the valve is in the closed position for several hours, say 8 to 10, and the system above or
below is evacuated, some difficulty may be experienced in opening the valve. This difficulty is due to
leakage of air into the valve housing. The air has sufficient pressure to prevent the gate from un-
seating when the cam pressure is released. A roughing pump connection to the valve housing makes
it possible to evacuate that volume and overcome this difficulty.




The ring (18) can be cemented to the quartz tube with Saureisen or Insalute cement (Central
Scientific Co.)
The figures in parentheses in this section refer to parts shown in Figure 5, unless otherwise
indicated.


10].









MDDC 1126


SOME ACCESSORY EQUIPMENT

The adaptation of standard plumbing valves for vacuum systems has been described by DuMond"'
and Rose.'" Both methods employ a sylphon bellows to prevent leakage along the valve stem. A
simpler method which the writer has found to be satisfactory is substitution of a Wilson seal for the
valve stem packing. The Kerotest valve commonly used in refrigeration installations and the Hoke
valve are needle-type valves which are suitable "as is" for use in vacuum systems.
In the same articles mentioned above, DuMond has described a flexible, noncollapsible sylphon
coupling and Rose has described a method of bolting together metal tubing. Garner'4 has also de-
scribed other methods of performing this operation.


OPERATION

The furnaces described in this report were connected to identical pumping systems. The systems
consisted of the following parts, connected in the order given: a metal baffle, a metal diffusion pump,
MC-275,* a metal booster pump, MB-15,t and a Megovac forepump running at double the normal
speed.
About 1/2 hour before making a run, the pumping system is started, with the gate valve closed.
After loading and closing the furnace it is "roughed out" to about 200 microns by a Megovac roughing
pump. The gate valve is then opened and the furnace pumped out to the desired pressure before be-
ginning the melt. Pressures of 10-3 to 10-4 mm Hg have been obtained with about 1/2 hours of pump-
ing depending on the amount, nature, and condition of the materials in the furnace. When the systems
were first constructed and before any melts were made, pressures of between 10-5 and 10-6 mm Hg
were obtained. If it is desired to run the pumping system continuously, or when no operator is in
attendance, it is advisable to install a safety device that will cut off the heaters in the oil pumps in
case of cooling water failure. Detroit pressure switches are used for this purpose.
The power input for the resistance furnace is controlled by a 28 amp Variac which is connected
to a 110 volt line. A maximum power input of only 2 kw, was sufficient to reach temperatures of 1400-
1500 degrees C. The maximum temperature of operation would probably be determined by the initia-
tion of a reaction between the tungsten or molybdenum winding and the alundum core (Figure 1-33).
Although no determination was ever made of the maximum rate of heating, charges of 500 to 1000 g were
heated to around 1400 degrees C in less than 30 minutes. Due to the fact that both tungsten and molyb-
denum wire are easily oxidized at elevated temperatures the furnace must be cooled to about 200 de-
grees C before opening to the atmosphere. The cooling period is greatly shortened by admitting an
inert gas into the system.
The crucible shown in Figure 1 has a volume of about 275 cc. Although this volume will hold about
2400 g of molten copper, for example, the capacity of the crucible is determined by the amount of metal
that can be initially charged into the crucible.
The power supply for the induction furnace was provided by a 10 kw. Thermonic high-frequency
converter. Very rapid heating is possible with this unit. Melts of 200-400g can be heated to 1400-1500
degrees C in less than 10 minutes. The refractory properties of the crucible would determine the
maximum temperature of operation rather than any feature of the furnace design.







Distillation Products Industries, Rochester, N. Y.
t Central Scientific Co.









12 ]
ACKNOWLEDGMENT


MDDC 1126


The designs and methods of construction which have been presented in this report were origi-
nated or developed by members of an entire group, of which the writer was a part, engaged in vacuum
melting and casting. It would be difficult if not impossible to trace each idea back to its originator,
but the following list includes those who made the most significant contributions in this work: G. L.
Butler, Noble Hamilton, Leonard Levinson, Shadburn Marshall, J. G. McChesney, A. U. Seybolt, Leston
Stark, and J. H. Wernick.


0 A
L- x


CROSS-SECTION THROUGH CENTER


Figure 5. Vacuum gate valve.

List of Parts for Figure 5


Material

Brass
Rubber
Brass
Brass
Brass
Brass
Rubber
Brass
Brass
Brass
Brass
Brass
Brass
Brass
Steel
Steel


Part (nominal dimensions in inches)

5- 3/4 OD x 4 ID Upper flange
1/8 x 1/8 Gasket
1/4 x 5-1/2 x 12-1/2 Upper plate of housing
3/8 Diam x 11 Rod
Collar
10-32 x 5/8 Filister head screw
1/8 x 1/8 Gasket
1/4 x 3-3/8 x 6-3/8 End plate of housing
1/4 x 2-1/2 x 5-1/2 End plate of housing
3/8 x 5-1/4 x 7 Guide plate
3/8 Cam
1/4 x 5 x 6 Lower gate.
3/8 Wilson seal
1V4 x 1/2 x 3 Handle
1/4 Diam x 1-7/8 Guide pin
Spring


Number









MDDC 1126


BIBLIOGRAPHY

General

1. Diergarten, Hans, Vacuum melting on a large scale, Metal Progress (1934).
2. Dushman, Saul, Recent advances in the production and measurement of high vacua, J. Frank Inst.
211:6:689 (1931).
3. Kroll, W. J., Melting and evaporating metals in vacuum, Trans. Electrochem. Soc. Printed also in
Canadian Metals and Metallurgical Industries 8:26-30 (1945).
4. Morse, R. S., Modern vacuum practice in electronics, electronics 12:11:33-6 (1939).
5. Strong, John, et al. Procedures in experimental physics, Prentice-Hall, Inc. New York Chap. mI.
1938.
6. Vick, F. A., Vacuum practice, Science Progress 33:83-7 (1938).

Vacuum Furnace Design

7. Arsem, W. C., The electric vacuum furnace, Trans. Electrochem Soc. 9:153 (1906).
8. Ehret, W. F., and David Gurinsky, A laboratory high vacuum furnace, R. Sci. Inst. 12:151-3 (1941).
9. Friauf, J. B., The purification of manganese by distillation, Trans. ASM 18:213 (1930).
10. Hultgren, Ralph and M. H. Pakkala, Preparation of high melting alloys with aid of electron bom-
bardment, J. App. Phy. 11:643-46 (1940).
11. Lowry, E. F., A vacuum annealing furnace of novel design, R. Sci Instr. 4:606-9 (1933).
12. Walters, F. M., Jr. Alloys of iron, manganese, and carbon-part 1. Trans. ASM. 19:577 (1932).

Accessory Equipment

13. Du Mond, Jesse, Two applications of the sylphon bellows in high vacuum plumbing, R. Sci. Instr.
6:285-6 (1935).
14. Garner, L., Machined metal stuffing box seals adapted to high vacuum technique, R. Sci. Instr.
8:329-32 (1937).
15. Henderson, M. C., A simple protective device for vacuum systems, R. Sci. Instr. 10-43 (1939).
16. Rose, J. E., Two aids in high vacuum technique, (1) Leak Proof Valve. (2) Leak Proof Joint,
R. Sci. Instr. 8:130 (1937).
17. Wilson, R. S.,A vacuum tight sliding seal, R. Sci. Instr. 12:91-3 (1941).
18. Youtz, J. P., A device to protect large vacuum systems from accidental interruptions of mechanical
pump, R. Sci. Instr. 9:420-21 (1938).

Leak-Hunting
19. Kuper, J. B. H., A vacuum gauge for leak hunting, R. Sci. 8:131-2 (1937).
20. Manley, J. H., L. J. Haworth, E. A. Luebke, Vacuum leak testing, R. Sci. Instr. 10-389;340 (1939).
21. Webster, D. L., Vacuum leak hunting with CO2, R. Sci. Instr. 5:42-3 (1934).


END OF DOCUMENT




UNIVERSITY OF FLORIDA
IIllllllllIIIIlllMII IIlIIIII i ll
3 1262 08907 9510






























.1
9 U




Full Text
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID EFCA464D1_O89Y1I INGEST_TIME 2012-02-29T16:21:16Z PACKAGE AA00009324_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES