Induction heating of metallurgical specimens to high temperatures in coil furnac

Geringer, H. J.

English

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WASHINGTON, D.C. 20546 
REPLY TO 
ATTN OF: GP 
ssistant Gene 
SUB 
Ln accordance wi h the procedures contained in the Code GP 
m on this subject, dated June 8, 1970, 
ed U . S ,  patent is being forwarded for 
and announcement in NASA STAR, 
lowing information is provided: 
U , S ,  Patent No. %0,30 
ate Source S c 
Supplementary 
Corporate Source 
NASA Patent ease No,: 26 
https://ntrs.nasa.gov/search.jsp?R=19710013791 2020-03-17T03:01:48+00:00Z
pt. 30, 1969 H. J. GERINGER 
INDUCTION FURNACE WITH PERFORATED TUNGSTEN FOIL SHIELDING 
Fi led  Feb. 16. 1967 
66 
0 
F I G .  2 
F I G .  3 
**..-- 
HENRY J. GERINGER $e. 
BY 
I 
of component parts which do not require close dimen- 
Another object of the invention is to provide a high 
temperature induction furnace which may be used with 
various gases or atmospheres. 
Still another object of the invention is to provide an 
induction furnace which is readily adaptable to rapid 
heating and cooling cycles. 
These and other objects of the invention will be ap- 
6 C l a i n ~  10 parent from the specification which follows and from the 
drawings wherein like numerals are used throughout to 
identify like parts. 
Description of the drawings 
FIG. 1 is a vertical section view of an induction fur- 
nace constructed in accordance with the present invention; 
FIG- is a Plan view of the furnace taken the 
line 2-3 in FIG. 1 showing the novel arrangement of 
the specimen, susceptor cup, split sleeve, foil shielding and 
20 container cup in an induction heater constructed in ac- 
Origin of the invention cordance with the invention; 
FIG. 3 is a sectional view taken along the line 3-3 
The invention described herein was made by an em- in FIG. 1 showing the manner in which the specimen is 
ployee of the United States Government and may be shielded in the furnace; and 
manufactured and used by or for the Government for 25 FIG. 4 is a sectional view taken along the line 4- 
governmental purposes without the Payment Of any in FIG. 1 showing the relative positions of the SUpPOrtS 
royalties thereon or therefor. and heat shields. 
Background of the invention Description of the preferred embodiment 
Referring now to the drawing, there is &own in FIG. 1 
ing of metallurgical specimens to elevated temperatures a specimen 10 which is to be inductively heated by a coil 
in an induction coil furnace. The invention particularly 12 of an induction furnace in a manner well known in 
relates to heating such specimens to  5000 to  6000" F. the art. The specimen 10 is contained in a susceptor cup 
without reactions between refractory materials. 14 which, in turn, is positioned in the induction coil 12. 
Induction coil furnaces make use of insulating re- 35 me susceptor cup 4 is of tungsten and has a floor 16 
fractory materials in the form of ceramics as well as pre- upon which the rests. A disposed 
cision made parts which are very close fitting. It has been opening 18 in the floor 1 nables an inert gas to pass 
found that certain test specimens react with the insulat- through the susceptor cup when the induction furnace 
ing material a t  the elevated temperatures to  which these is operated in an environment containing such a gas. 
specimens are heated. Also, these conventional furnaces 40 ne susceptor cup 14 and specimen 18 must be properly 
are constructed in such a manner that Certain gases and shielded and insulated from the coil 12 and other furnace 
atmospheres cannot be added during heating because of parts at high operating temperatures between 5000" and 
the danger of reaction with the Ceramics at the Very high 6000" F. to prevent overheating and the resulting damage 
temperatures which would reduce or volatilize the ceramic to the various furnace components. This is accomplished 
materials. on by enclosing the specimen IO and 
Certain of the ceramic insulators having high tempera- the susceptor cu in a split container cup 20 which is 
ture capabilities are radioactive or toxic and are danger- also fabricated angsten sheet and then positioning 
ous to operating personnel. Also, this material breaks the cup 20 in the coil 12. Susception in the cup 
down even when used only in vacuum because of thermal 20 is minimized by a slot 22 extending along its entire 
cycling and the accompanying thermal expansion and 50 length. The CUP 20 has a generally cylindrical configura- 
contraction. The sensitivity of ceramic insulation to tion as shown in the drawing, and its outside diameter is 
damage from thermal gradients prevents use of rapid smaller than the inside diameter of the coil 12 to  facilitate 
heating and cooling cycles in the furnace. Shielding insertion. 
present-day induction furnaces is complicated and costly 
with delays and equipment downtimes being encountered. 55 25 forms the bottom of the container cup 
Also, the ceramic insulators utilized in conventional fur- 
nace designs sometimes melt or outgas making attain- 
ment of high vacuum impractical when operating at very 
high temperatures. 
Summary of the invention 
These problems and difficulties have been solved by an 
induction heater constructed in accordance with the pres- 
ent invention. A split cup containing loosely coiled 
tungsten foil is utilized in the present invention instead Of 65 
precision radiation shields and spacers used in prior art 
furnaces. This split Cup forms a holder for either a SUS- 
ceptor cup or a billet which is to be inductively heated. 
Objects of the invention 
It is, therefore, an object of the present invention to 
provide an induction furnace having a minimum number 
,470, sional tolerances. 
PN ACE 
FQI 
Henry J. Geringer, Brnnswick, Ohio ta the 
United States of America as represented by the Admin- 
Aeronautics and Space 
A ~ m ~ i s ~ a ~ o n  
of the 
Filed Feb. 16, 1967, Ser. No. 617,770 
Put. CI. H05b 5/16 
U.S. CI. 13-26 
tween its coil and the specimen which is to be heated. 15 
The foil is perforated to minimize susception, and it is 
loosely wound into a tubular configuration about the 
susceptor or specimen. 
This invention is concerned with the induction heat- 30 
45 in the present 
A tungsten 24 having a radially e 
cylindrical support 26 of tungsten is secured to the bot- 
tom of the 
The split container cup 20 is removed from the coil 
12, and the bottom edge of the support 26 is placed on a 
6o flat surface remote from the furnace. A tungsten sup- 
port 28 having a triangular shape is placed on the plate 
24 at the bottom end of the split container cup 20. The 
triangular support 28 is separated at one comer to inhibit 
susception. 
30 is placed on &e triangular sup- 
port 28. The disk 38 has a diameter slightly smaller than 
the inside diameter of the container cup 20 and a thick- 
ness of one mil. 
An important feature of the invention lies in the fact 
70 that the foil disk 30 is perforated to minimize suscep- 
tion. This perforation is accomplished by placing the foil 
between two abrasive sheets, such as 50D garnet paper, 
24 as shown in FIG. 1. 
A tungsten foil 
3.470,304 
and passing this assembly through a pair of pressure 
rolls. 
Various specimens 1 which are to be heated will differ 
in size. Likewise, the susceptors 4 have different lengths 
to accommodate specimens of various lengths. Each 
specimen 10 is matched with a susceptor 14 having the 
proper length. 
The susceptor 14  and specimen 10 should be located 
approximately at the center of the split container cup 20 
for optimum heating. Consequently, the number of tri- 
angular supports and foil disks required will vary. Also, 
triangular supports having different widths may be used. 
For example, in the embodiment shown in FIG. 1, a 
second triangular support 32 which is the same as the 
support 28 is placed in contact with the disk 30. A 
second foil disk 34 is then placed on the triangular sup 
port 32. 
Still another triangular support 36 is placed o n x e  
disk 34, and a similar disk 38 is 
surface. A smaller triangular supp 
foil disk 38. Another perforated 
on the triangular support 40. 
It will be noted from FIG. 1 that the triangular sup 
port 40 is considerably narrower than the other tri- 
angular supports 28, 32 and 36. FIG. 4 shows that the 
triangular supports are staggered when they are placed 
on top of one another in order to insure stability. With 
this arrangement the foil shields 30, 34, 38 and 42 act 
as heat barriers while the triangular supports 28, 32, 36 
and 40 properly position the susceptor cup 14 and the 
specimen 10 within the split container cup 20. 
4 having a thickness of 
about .020 inch and a radially extending slot 45 is then 
placed over the foil disk 42 for added rigidity. Another 
triangular support 46 is placed on this plate. The thick- 
ness of the triangular support 46 is approximately the 
same as that of the triangular support 40, and the length 
of each of its legs is shorter than the lengths of the 
corresponding legs of the other triangular supports. An- 
other perforated tungsten foil disk 48 having a reduced 
diameter is placed on the support 46. 
A perforated disk 49 of one mil tungsten foil is placed 
over the opening 18 in the bottom plate 16 of the 
susceptor cup 14. A specimen 10 is then placed in the 
susceptor cup 14 on the foil disk 49, and the assembly 
is ready for positioning in the split container cup 20. A 
pair of lifting hooks or the like engage opposed holes in 
the susceptor cup 14 near the uppermost end. The 
susceptor cup 14 and specimen 10 therein are picked 
up by the lifting hooks and properly centered in the split 
container cup 20. 
A split sleeve 50 made from a sheet of tungsten having 
a thickness of about 0.020 inch is then inserted into the 
container cup 20. around the susceptor cup 14 and tri- 
angular support 46. A slit 52 inhibits susception in the . This slit is produced by separating the op- 
posed edges of the sleeve 50 when it is formed from 
tungsten sheet. 
One of the novel features of the invention is the utiliza- 
for shielding and insulating the 
foil 54 has a thickness of one 
mil and is perforated in the manner previously de- 
scribed to inhibit susception. The foil 54 is loosely 
wound to a cylindrical configuration and placed about 
the split sleeve 50 which maintains the foil out of con- 
tact with the susceptor cup 14. 
A pair of chevron spacers 56 and 58 in the form of 
bent strips of tungsten are positioned between the foil 
shield 54 and the inside surface of the split cup container 
20 on diametrically opposed sides of the specimen 10 as 
shown in FIGS. 2 and 3. These spacers prevent the foil 
shield 54 from unwrapping and contacting the split con- 
tainer cup 20. The contact between the foil shield 54 
and the inner surface of the split container cup 20 is 
further minimized by providing an inwardly turned flange 
A circular tungsten plate 
4 
on one edge of the slit 22 in the split container cup 20 
as shown in FIGS. 2 to 4. 
A split ring 60 of tungsten is placed about the periphery 
of the upper edge of the sleeve 50 to cover the space 
between the sleeve and the split container cup 20 con- 
taining the foil shield 54. The split ring 60 is maintained 
in position by another split ring 62 which engages the 
upper surface of the split ring 60. 
After all the components are assembled in the man- 
10 ner shown in FIG. 1, the entire assembly is positioned 
in the center of the coil 12. This is accomplished by utiliz- 
ing a pair of lifting hooks 64 shown in FIG. 1. The legs 
of the hooks engage suitable holes which extend through 
the split container cup 20 adjacent the upper surface. 
The assembly is accurately positioned within a coil 12 
by utilizing a three-legged base plate 66 which rests on 
the bottom or floor of the furnace. A tapered upper sur- 
face on the base plate 66 engages the bottom edge of 
the support 26. The upper end of the split container cup 
20 20 is then covered by a perforated foil disk which is 
preferably attached to the furnace cover which encloses 
the coil 12. The base plate 66 is preferably stainless steel 
while all of the other components of the furnace are 
tungsten. The majority of the tungsten structural ele- 
25 mens have a thickness of .020 inch. The foil has a thick- 
ness of one mil as pointed out above. 
While a preferred embodiment of the improved furnace 
shielding has been shown and described, it will be ap- 
preciated that various structural modifications may be 
30 made without departing from the spirit of the invention 
or the scope of the subjoined claims. For example, the en- 
tire assembly can be suspended within the coil 12 by 
providing a suitable support for the hooks 64. Also, when 
the specimen 113 is in the form of a billet it may be heated 
35 directly without the use of the susceptor cup 14. In this 
case the sgi t  sleeve 50 is placed around the billet, and 
the foil shield 54 encircles the sleeve as shown in the 
drawings. 
15 
What is claimed is: 
1. In a high temperature induction furnace having a 
coil for receiving a specimen to be heated, the improve- 
ment comprising 
layers of perforated tungsten foil adjacent the specimen 
40 
for heat shielding the same, and 
45 
50 
means for supporcmg said foil layers when the speci- 
2. Apparatus as claimed in claim 1 including a sus- 
ceptor cup for supporting the specimen in the coil. 
3. Apparatus as claimed in claim 2 wherein the sus- 
ceptor cup and thin foil are of the same material to 
prevent contamination of the specimen. 
4. In a high temperature induction furnace having a 
coil for receiving a specimen to be heated, the improve- 
men is positioned in the coil. 
ment comprising 
55 layers of thin foil adjacent the specimen for heat shielding the same, and 
means for supporting said foil layers when the speci- 
men is positioned in the coil comprising a split con- 
tainer cup having a slot extending along the entire 
length. 
5. Apparatus as claimed in claim 4 including heat 
shields at one end of the split container cup. 
6. In a high temperature induction furnace having a 
coil for receiving a specimen to be heated, the improve- 
65 ment comprising 
a susceptor cup for supporting the specimen in the 
coil, 
layers of perforated foil adjacent the specimen for 
heat shielding the same, both said susceptor cup and 
said perforated foil being of the same material to 
prevent contamination of the specimen, and 
means for supporting said perforated foil layers when 
the specimen is positioned in the coil. 
75 eferelnces on following page) 
‘O 
70 
3,470,304 
eferenees Cited 
UNITED STATES PATENTS 
3,036,888 5/1962 Lowe _ _ _ _ _ _ _ _ _ _ _ _  219-10.49 
3,162,710 12/1964 Anderson _ _ _ _ _ _ _ _ _ _ _ _  13-27 
3,409,730 11/1968 Ebihara _ _ _ _ _ _ _ _ _ _  13-30 X 5 219-10'.49 
J. SPENCER OVERHOLSER, Primary Examiner 
ROBERT D. BALDWIN, Assistant Examiner 
U.S. C1. X.R. 


Induction furnace with perforated tungsten foil shielding Patent

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