Патент USA US2124573код для вставки
Patented July 26, 1938 2,124,573 UNITED STATES $ PATENT OFFICE : 2,124,573 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. 25 It is the principal object of my invention'to provide a simple arrangement that ‘facilitates the ?lling of a furnace chamber with a desired 3 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. I 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. i ‘ 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. m 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 struction. 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 . 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, eliminated. 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. 20 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 35 retained in the interstices of the insulating mate 4. In combination, a heat treatment chamber, rial. ‘ walls of porous material therefor, means for con; The above described construction therefore ' ducting products of combustion of predetermined ber. ~ 1 e _ 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. ' CARL I. HAYES.