US3475014A - Vacuum/inert gas quenching chamber - Google Patents

Description

Oct. 28, 1969 A. l.. FRANK ET AL 3,475,014-

VACUU/INERT GAS QUENCHING CHAMBER Filed March 2, 1967 Q QW mgl ww United States Patent O U5. Cl. 266-4 5 Claims ABSTRACT OF TI-Illl` DISCLOSURE An extended, sealed heating chamber is provided in which rides a refractory boat or specimen holder with external means for lengthwise movement of the holder. One end of the chamber is provided with a closed depending extension. The chamber walls carry a pair of inlets one of which extends to the opposite end of the chamber and each having a control valve and the base of the extension is adapted to accommodate a pair of valved, sealed iluid inlets. Additionally, a means for heating the chamber is disposed external thereto and may constitute an induction coil or the end of the chamber distal from said extension placed into a heating furnace. Initially the specimen is disposed in the holder proximate the end of the chamber distant from the extension and a high or hard vacuum is drawn within the chamberafter the chamber has been alternately evacuated and ushed with inert gas through the valved inlets so as to remove completely any residue of any contaminating atmosphere therein. The specimen is then heated by way of the chamber to any desired temperature. On completion of the heating cycle, the specimen can be cooled directly insitu by introducing inert gas through a controlled valve. The rate of cooling can be likewise selected by the introduction of the inert gas at a predetermined temperature. Thus, it is simple to simulate cooling by the surrounding air as is done in production. On the other hand, where rapid quenching is necessary, the inert gas is introduced as well as oil, water, Freon or any fluid media into the depending extension. The specimen is then dropped on to a screened platform therein to complete the quenching without boiling oif the media due to a surrounding vacuum.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Background of the invention (l) The invention relates to furnace muliles and quenching chambers for controlled heating, cooling and quenching of highly reactive metal specimens without contamination thereof and unaffected by the type of quenching media.

(2) There presently exist two well-known techniques for heat treating laboratory samples of reactive metals. The first includes encapsulating the sample in a vycor tube, while the second involves heating the sample using strip heaters all enclosed within an evacuated glass chamber. These techniques have been used for delineating phase boundaries and for developing preliminary heat treatment data for new alloys and highly reactive metals. With regard to the first method, the encapsulated sample must be removed from the furnace before it may be plunged into the quenching media for rapid cooling. This results in the breaking of the vycor tube and exposure to contaminating atmospheres. In the evacuated chamber method the specimen is suspended on a thermocouple under a quenching port and heated by the surrounding strip heaters. No provisions are made for the introduction of any inert gas or gaseous atmosphere in this process. Furthermore, there is no provision for a controlled rate of cooling.

Summary of the invention The invention includes a method and structure for heating and quenching a highly reactive metallic specimen without contaminating the specimen and controlling the cooling rate thereof. The structure includes in combination, a sealed chamber having a depending quenching portion and a number of valved inlets for the introduction to the chamber of an inert gas and evacuation thereof and ports at the base of the quenching portion. The chamber carries internally thereof a titanium specimen holder whose movement is controlled from the outside. The base of the quenching portion supports a screen platform for supporting the specimen and for free circulation of the quenching media. The method includes purging the chamber and then providing a vacuum therein. The entire chamber is heated or cycled through the desired temperature range as in a furnace. The specimen is then cooled by either of two procedures. If air cooling is to be simulated, then an inert gas of the selected thermal capacity and at a predetermined temperature is introduced at a known rate. Where a rapid quenching is desired, the chamber is filled with an inert gas and the specimen holder is moved over the quenching portion after the quenching media has been introduced. The specimen is then dropped into the media for rapid cooling.

Brief description of the drawings In the accompanying drawings:

FIG. 1 is a side view in cross-section of an embodiment made in accordance with the principles of this invention, and

FIG. 2 is a cross-section view of the forward portion of another embodiment.

Description of preferred embodiments In the embodiment of the invention of FIG. 1 a mutlle 10 consisting of a chamber 11 closed at the forward end 12, carries therein a specimen holder or boat 13 which is of a refractory material such as titanium. The muiile |10 may be circular in 'cross-section but any cylindrical shape is satisfactory. The chamber 11 is joined to a T section 14 by either a weldment or, as shown, by being threaded therein and sealed by an O ring 15. The end 16 of the T 14 opposite the muflle 10 is also provided with an internal threaded portion 17. The plug body 18 is threaded into the T 14 so as to close that end of the T. This plug 18 as Well as the T 14 may be welded to provide a positive high pressure seal or as shown sealed by means of an elastomeric O ring 19. The plug body 18 has a pair of lengthwise openings 20 and 21, one being central of the plug. In the central opening 20 is disposed a tubular viewing member 22 which terminates in an eyepiece 23 which carries therein a dark lens 24 for visually observing the specimen While it is at elevated temperatures. The viewing member 22 is welded to the plug 18 as at 25 and is in line with the specimen 26 for proper viewing thereof. The other opening 21 is closed at its outer end by a stuffing tube 27 or any other suitable sealing arrangement through which outwardly passes a stil Icontrol titanum wire 28. The opposite end of this control wire is rigidly fixed to the specimen holder 13. The stufling tube 27 permits lengthwise movement of the control Wire while maintaining the pressure integrity of the mufe and permitting the holder to be transported to and fro by means external of the portion of the wire.

The lower portion 29 of the T 14 carries an upper support member 30 which is threaded therein and sealed by O ring 31. This support is generally tubular and has an outer ange 32 which is provided with an annular recess 33 and an outer edge 34 having oppositely disposed passageways 35 and 36 therethrough. The lower portion 29 of the T and the support member 30 have aligned inner openings so as to provide direct communication with the chamber 11.

Disposed below and distal from the support 30 is a lower platform support or base 37 which like the upper support has an annular recess 38 and an outer edge 39 having a pair of passageways 40 and 41. These elements are all aligned with those of the upper support and are in facing relation thereto. Recessed in the annular grooves 38 and 33 and supported between the platform and the upper support is a tubular hollow transparent plexiglass member 42. In order to seal this member O rings 43 and 44 are seated in the annular grooves. The entire assembly is referred to as a depending portion which serves as the quenching chamber and is rigidly xed therein by the locking bars 45 and 46. These bars, as shown, are a pair of long bolts having a head at one end and threaded at the other end. They pass through the aligned holes in the edges 34 and 39 and are tightened by wing nuts 47 and 48 so as to permit disassembly of the quenching chamber.

The base 37 carries a pair fluid ports such as tubes or pipes 49 and 50 which pass therethrough into the chamber and are open therein and welded thereto. The outlet port 50 terminates at the base upper surface 51 while the inlet port 49 extends into and almost upwardly to the upper support 30. Valves 52 and 53 control the passage of fluids into and out of the quenching chamber and are connected to a source of quenching media and a sink therefor, respectively.

Disposed on the base surface 51 is an open screen platform 54 supported on legs 55. This screen platform permits the free passage and circulation of the quenching fluid while supporting the specimen as will be explained hereinafter.

The opposite side of the T 14 is provided with three openings 56, 57 and 58. The iirst opening 56 carries a pipe inlet 59 welded therein which terminates at the inner face of the T 14 and serves as an exhaust to provide a hard vacuum within the muiile when connected through valve 60 to the vacuum pump. The second opening 57 permits the passage therethrough of thermocouple cable 61 via a sealing gland 62. The inner end of the thermocouple cable is connected to a thermocouple sensor 63 adjacent or in contact with the specimen so as to allow measurement of its temperature. The external portion of the cable is connected to a pyrometer 64. Through the third opening or inlet 58, which is closest to the forward end 12 of the muie, passes another welded pipe 65 whose inner portion 66 extends lengthwise of the mufe and terminates proximate the forward end wall 12. From a source of inner gas 67, via control valve 68 an inert atmosphere can be introduced into the muiiie. It should be noted that the inert gas enters at the forward and proximate the specimen while the muflle is simultaneously exhausted (vacuum) at the opposite end so as to provide proper circulation and complete purging.

The mutfle may be heated by direct insertion of the forward portion thereof into a temperature controlled furnace or it can be heated as illustrated in FIG. 2. An induction coil 69 is placed around a dielectric insulating sleeve 70 which abuts and completely surrounds the outer iron wall of the mue. The coil is connected to a source of high electric current 71 so as to inductively heat the muflle wall and the interior thereof including the specimen.

The following general description of the operation of the above-described embodiments is intended to clarify the interaction of the device elements. The muiile chamber can, if desired, be constructed of an iron pipe which is capped at one end and threaded at the opposite end with a T coupling. A detachable transparent quenching chamber is fitted to the pendant cross opening of the T fitting while the remaining open end of the T is provided with a plug carrying a viewing member. Although it is preferable t0 weld and braze all the structural connections in order to maintain a high degree of pressure integrity, the proper use of threaded connections sealed with O-rings can be used with the attendant benet of easy disassembly.

Clearly the operation of this device is dependent on the particular heat treatment cycle desired. The specimen and the boat are introduced into the chamber with the manipulator control wire, the thermocouple attached, and the chamber then sealed. After the muffle has been positioned in the furnace or within the induction coil, it is advisable to check all the valves and fittings for proper sealing to prevent any leakage. The chamber is alternately evacuated via the vacuum pump and valve 60, and flushed with inert gas (source 67 and valve 68) to remove any contaminating atmosphere. This purging operation should be done, it has been found, at least three times. It should be noted that extremely eflicient purging is accomplished due to the physical arrangement of the vacuum and inert gas inlets. Complete circulation, without any trapping of gas, occurs since the gas inlet and the vacuum port are at opposite ends of the chamber.

After the chamber has been completely purged, it is pumped to a high vacuum against the inert gas and the specimen and chamber are heated to the selected temperature. On completion of the heating cycle, the specimen may be cooled in situ by the introduction of an inert gas at a predetermined temperature and at a rate so as to simulate any desired form of industrial or production cooling or may be rapidly quenched.

Where rapid quenching is employed any well known quenching media, such as water, oil or Freon, is introduced into the upper end of the quenching chamber via port 49. This is done only after inert gas is present within the chamber since under an evacuated condition the quenching media would tend to boil and vaporize thus affecting the specimen. Circulation of the media continues since it can be continually removed via outlet 50 thus maintaining a high proportion of a constant temperature media in contact with the specimen. The specimen is placed into the quenching chamber by pulling the manipulator control wire 28 outwardly of the mule and twisting the wire when the boat is disposed above the quenching chamber and tipping the specimen therein. The specimen falls on to the screen platform 54 and thereby permits the media to freely circulate and remain in contact with the entire surface of the specimen.

From the foregoing description it is clear that the mufile not only permits greater control over heat treating parameters but also allows a wide degree of heating and cooling rates. A wide latitude is available with respect to selecting and controlling of the internal atmosphere as for example nitriding, carburizing, endothermic and exothermic atmospheres. Since specimens of various materials are to be used, the chamber itself can be readily changed to one of a material which is not reactive with the specimen or where high temperature porosity is a factor.

It will be understood that various changes in the details, materials, and arrangements of parts (and steps), which have been herein described and illustrated in order to explain -the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

We claim:

1. A muflie for heating and cooling a specimen under selected environmental conditions which comprises:

an elongated hollow chamber closed at one end,

a depending quenching chamber extension closed at one end by a base and having the opposite end aixed to and proximate the other end of said chamber with the interiors thereof in direct communication,

a plug closing said other end of said chamber,

a pair of inlets for communication with the interior of said elongated chamber, each inlet having a control 6 valve for selectively sealing and opening said inlets, a specimen holder of a refractory material, one of said inlets extending to said one end of said means for moving said holder lengthwise in said muiiie chamber and the other of said inlets disposed at the and controlling such movement externally of said other end of said chamber, muiiie.

a pair of fluid ports carried by said base, each inlet 5 4. The muie according to claim 3 wherein said means having a control valve for selectively sealing and for moving is a control Wire having one end thereof opening said port, one of said uid ports extending affixed to said holder and the other end passing through through said base and terminating proximate said and outwardly of said plug. opposite end of said quenching extension, the other 5. The muie according to claim 4 further including: of said iluid ports terminating on the inner face of a dielectric insulating sleeve surrounding the outer Wall said base, of said chamber,

a screen platform disposed on said base for supporting an induction heating coil disposed about said sleeve,

said specimen when in said extension and permitting a source of electrical current connected to pass a high free circulation of said quenching media, current through said coil and thereby heat said chamwhereby a specimen may be introduced into said chamber and said specimen therein.

ber, said chamber purged by introducing an inert gas through said one inlet and evacuated through said References Cited other inlet, the chamber heated to a desired tempera- UNITED STATES PATENTS gre, and the specimen then quenched by lntroducmg l 610,022 8/1898 Bovensiepen 266 4 X rough said one uid port a quenchlng media mto said extension after said chamber is filled with an 2063784 12/1936 Bechtel et al 266- 2 X 3,016,314 1/ 1962 Kellerman 266-4 X gas, and plaClDg Sald SpCClmeIl IDO Sald CXSII- 3, Fulton* 2. the mule according to claim 1 wherein the walls of said quenching extension are of a transparent material. J SPENCER OVERHOLSER Prlmary Exammer 3. The mule according to claim Z further including J. S. BROWN, Assistant Examiner therein:

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