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Патент USA US2124573

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Patented July 26, 1938
ENVELOPING Amosrnuan common
Carl 1. Hayes, Providence, m1.
Application October 21, 1936, Serial No. 106.751
.liClaims. (01. 266-4)
any variation creates a deleterious effect on the
My present invention relates to the heat treat
ing art, and has particular reference to a novel material and on its surface condition because'of
control of enveloping atmosphere for materials the resultant chemical reaction. Since modern
furnaces are heavy insulated, and this insulation
undergoing heat treatment.
The present heat treating art includes the is of porous material, it has been found that the I _
placing of material for heat treatment within a enveloping atmosphere will permeate throughout
furnace chamber, and enveloping the material the insulation material, whereby a change‘ to a
in a gaseous atmosphere having a predetermined different enveloping atmosphere for heat treat
ing a different material requires a de?nite
constituency, the material and the enveloping at
period of time before the gases in the insulating
10 mosphere being subjected to regulated heat.
material are replaced by the gases forming the
Since the enveloping atmosphere must be se
lected so as not to react with the material under
going heat treatment, dii’ferent materials require
enveloping atmospheres with different constitu
15 encies, whereby the change from one material to
another in normal commercial heat treating re
quires a change of atmosphere; the new atmos
phere should completely replace the previous at
mosphere before the new material is subjected
20 to heat treatment.’ Moreover, 'unless a furnace
is worked continually, the shut down at night
causesa permeation of the furnace with atmos
pheric‘ air which should also be removed before
material is inserted therein for heat treatment.
It is the principal object of my invention'to
provide a simple arrangement that ‘facilitates
the ?lling of a furnace chamber with a desired
new enveloping material and a stable condition is
reached. A similar condition occurs when fur
naces are shut down at night, as the atmos
pheric air penetrates'into the insulating lining, 1‘
whereby it has been found that a considerable
period of time is necessary before the heat treat
ing atmosphere within the heat treating chamber
is properly stabilized. It has thus been found in
practice that a period varying from one to four 20
hours is necessary before the furnace begins to
function at its highest heat treating e?lciency, if
started up in the morning; and that a similar
time interval is necessary before a change in at
mosphere is made in order to heat treat a dif- 25
ferent material.
Thus, it has heretofore been di?icuit to utilize
a furnace for the heat treatment of tool steel, as
enveloping atmosphere. It is a further object of
my invention to provide simple and effective an alloy steel of the high chrome high carbon type
means for preventing admixture of contaminat ' requires an atmosphere containing a high CO 30
ing gases with the atmosphere required for the percentage, and a carbon steel of the chisel and
work undergoing heat treatment. It is an addi
tional object of my invention to provide a simple
arrangement whereby the furnace may be
35 speedily ?lled with the proper atmosphere for the
material to _be heat treated.
With the above and other objects and ad
vantageous features in view, my invention con
sists of a novel method and a novel arrangement
40 of parts more fully disclosed in the detailed de
scription following, in conjunction with the ac
, companying drawing, and more speci?cally de
?ned in the claims appended thereto.
die steel type requires an atmosphere containing
a substantial percentage of free oxygen.
I have therefore devised ‘an arrangement
which facilitates the replacement of one atmos
phere in a heat treating furnace with'another at
mosphere, and which prevents contamination of
the second atmosphere by the ?rst, whereby the
speed of changing from heat treatment of one gs
material to heat treatment of another material is
greatly increased, and the time hitherto neces
sary to fully remove atmospheric air after a shut
down is practically eliminated.
Referring to the drawing, an illustrative heat
treatment furnace II is shown, comprising a cas
Fig. 1 is a sectional view of a muille type fur
ing II in which insulation I2 is mounted around
nace embodying the novel invention;
Fig. 2 is a sectional view on the line 2-2 of a heat treatment chamber ll, the chamber hav
ing a throat ll through which work may be in
Fig. 1; and
serted and removed,,with a closure door jl5 of
.Fig. 3 is a sectional view of a modi?ed con
standard type. A combustion chamber I6 is posi- 50
In the drawing:
The proper heat treatment for materials has
been found to include: the use of an enveloping
atmosphere that will not react with the material
during the heat treatment. This enveloping at
mosphere is different for different materials and
tioned adjacent the heat treating chamber, pref
erably so as to be preheated thereby, and is
supplied with air and gas in regulated quantities
so as to obtain combusted products of predeter-v
mined constituency which pass upwardly through 56
. 2,124,573
an opening I ‘I, such as a slot extending across
mit a reasonably free ?ow of such gases to the
the throat, into the heat treating chamber to
form an enveloping atmosphere for the work
therein and to exclude the entry of atmospheric
air into the heat treating chamber, as explained
in my prior Patent No. 1,724,583 granted August
13, 1929. The heat treating chamber is prefer
suction producing means, whereby all tendency to
?ow back into the heat treating chamber is
ably heated by electrically heated elements l8,
While I have described a speci?c embodiment
of my invention illustrated as a mu?le type fur
nace, it is obvious that changes in the construc
tion and arrangement of the parts for different
but may be heated in any desired manner, the ' types of furnaces may be readily made, without
10, heating being suitably regulated and controlled . departing from the spirit and the scope of the 10
to obtain thedesired temperature in the cham
ber. As shown in Figs. 1 and 2, the casing I I has
a plurality of openings l9 extending there
through, and a second casing 20 is positioned
15 around and spaced from the casing || so as to
invention as defined in the appended claims.
I claim:
1. The method of preventing contamination of
an enveloping atmosphere in a heat treatment
chamber from gases in the insulation thereof, 15
provide a surrounding chamber 2|, this cham
comprising the step of reducing pressure at the
ber 2| having aiplurality of openings 22 com
outer portion of the insulation to a pressure less
municating with conduits 23 connected to a suc
than the pressure within the chamber to prevent
tion pump 24.
. inward flow of gases therefrom.
When the furnace is started up in the morning,
2. In the heat treatment of materials in a 20
or when it is desired to change the enveloping at
chamber having walls of porous material, the step .
mosphere, the pump 24 produces a diminished of in?owing an enveloping atmosphere of com
pressure within the chamber 2| and thus pro
busted gases into said chamber and simultane
duces a suction effect on the insulating material ously subjecting the outer surfaces of said walls
25 l2, which induces a flow of the atmosphere in, to a reduction in pressure to a pressure less than
the insulation material into the chamber 2| and the pressure within the chamber, to induce out-l
to exhaust from the pump 24. The use of. re
ward flow of gases through said walls.
duced pressure in the chamber 2| thus e?’ec-v
3. In combination, a heat treatment chamber,
tively prevents any reversed flow of permeated walls of insulating material therefor, means for
30 gases from the insulating material back into the conducting products of combustion of predeter 30
heat treating chamber l3. whereby the entry of mined constituency into said chamber to form
gases of predetermined constituency through the an enveloping atmosphere, and means for sub
opening l1 into the heat treatment chamber jecting the outer walls of said insulating material
cannot be contaminated by seepage of air and to a pressure less than the pressure in said cham
gases of different constituency which have been
retained in the interstices of the insulating mate
4. In combination, a heat treatment chamber,
walls of porous material therefor, means for con;
The above described construction therefore ' ducting products of combustion of predetermined
_ permits an immediate use of the furnace after a ' constituency into said chamber to form‘ an en
40 shut down or after a change from one enveloping
atmosphere to a different atmosphere, and en
veloping atmosphere, and means for producing
.a differential pressure between _ the inner and _
, sures operation of the furnace at maximum cf
outer walls of said porous material.
?ciency during the entire heat treating period. ' , 5. In combination, a heat treatment chamber,
Although I have described the use of a casing walls of porous insulating material therefor, a
45 || within which the insulating material I2 is‘ passageway chamber surrounding said insulating
mounted, the casing II and its openings l9 may
be omitted in certain constructions, as the insu
material, means for conducting products-of com
bustion of‘ predetermined constituency into said
lating material is self supporting; and insmaller
heat treatment chamber to form an enveloping
atmosphere, and means‘ for exhausting gases
from said passageway chamber.
types of furnaces it is feasible to use‘ a casing .25.
50 see Fig. 3, enclosing the insulation“, and pro
vided with a plurality of ports 21 communicating
with conduits 28 which lead to a pump or other
suction means-(not shown) ; the thickness of the
insulation, which varies from 5 to 15 inches de
65 pending on the temperatures for which the fur
nace is designed, as for example from 1600° to
2300“ F., is su?icient to cause the insulation to
function directly as a passageway means for the
gases which have penetrated therein, and to per
6. In combination, a heat treatment chamber,
walls of porous material therefor, means for con
ducting gases of predetermined constituency into
said chamber to form an enveloping atmosphere,
and ‘means for creating a pressure differential
between the chamber and the surrounding wall
material to induce ?ow of gases outwardly from
said‘ chamber through said material.
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