US2483803A - High-pressure and high-temperature test apparatus - Google Patents

Description

Patented Oct. 4, 1949 v HIGH-PRESSURE AND HIGH-TEMPERATURE TEST APPARATUS Percy W. Bridgman, Cambridge, Samuel S. Kistler,

West Boylston, and William Wheildon, Jr., Framingham, Mass., assignors, by direct and mesne assignments, to Norton Company, Worcester, Mass., a corporation of Massachusetts Application November 22, 1946, Serial No. 711,572 6 Claims. (01. 73-154) The invention relates to methods and apparatus for heating and pressing.

One object of the invention is to provide a method for subjecting material to a great pressure while heated. Another object of the invention is to provide an apparatus for heating and pressing simultaneously. Another object is to perform a series of chemical reactions producing intense heat in a closed chamber under great pressure. Another object is to provide an automatic detonating apparatus to detonate a charge responsive to subjecting the apparatus to great pressure. Another object is to provide a charge which will react to produce high temperatures under pressure of the order of many thousands of atmospheres. Another object is rapidly to produce high temperature under great pressure. Another object is to provide reaction charges and a mechanism for starting the reactions under enormous pressure without the use of any external connections so that the reactions can take place in a closed mold. Another object of the invention is to provide a satisfactory detonator to set ofi a charge under high pressure. Another object of the invention is to provide a satisfactory igniter charge or starter charge which will be ignited by the detonator and will set ofi the main charge under high pressure. Another object of the invention is to provide a main charge which will be set off by the igniter charge under conditions of great pressure. Another object is to provide a detonator and charges which will operate under great pressures and in which the charges will react substantially to completion under these pressures. Another object is to provide an apparatus and method for geophysical research. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps, to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings illustrating one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a cross sectional view taken along the axis of a mold constructed in accordance with the invention and showing the retaining plates of a press which support the mold.

Figure 2 is another cross sectional view of the mold of Figure 1 on a larger scale.

.2 Figure 3 is a third axial sectional view of the interior of the mold on a further enlarged scale to show the construction in better detail.

The apparatus of the invention is used in an hydraulic press. The press should be capable of exerting a thrust of five hundred tons. Referring to Figure 1 the press, not shown, holds a plurality of superimposed steel plates I!) having a continuous conical bore II extending there-- through, whereby the plates encircle and reinforce a central cavity block 12 which constitutes a mold. The thrust against the mold I2 is upward and as will be seen the mold l2 has a conical surface 13 which fits the conical bore H, the lower end of the mold l2 and of the bore l I being of larger diameter than the upper end of the mold and the bore. Thus upward pressure on the mold l2 tends to drive it into the bore H so that the reaction of the plates it exerts a compressive force radially inward of all parts of the mold l2.

We provide a specimen piston or ram i of small diameter, which exerts the pressure in the mold l2. This piston or ram 15 may rest upon a block l6 of some hard and strong material such as cemented tungsten carbide. An annular piece of steel [8 constitutes a retainer for .the block l6 and prevents it from splitting. The retainer I8 is centered on the top of a ram head by means of a centering ring 2|. We may also provide a centering ring 22 for visually centering the piston or ram IE on the block l6.

As shown, the ram head 20 is supported by a pair of semi-annular steel blocks 25 surrounding an auxiliary ram piston 26 to which the head 20 is removably secured by means of a bolt 21. The auxiliary ram 26 is movable in a cylinder 29 in the main hydraulic ram 30. Upon the top of the main hydraulic ram 30 is a removable ram head 3 I having a hole therethrough to receive the auxiliary ram 26. v

The foregoing construction is not per se our invention and may be varied widely. The use of the auxiliary ram 25 and the semi-annular blocks 25, which are removable, makes itpossible to move the specimen piston or ram [5 through a comparatively long distance at low pressure and under accurate control, and also rapidly. In other words, this is an expedient for mold I2, and the large end of whichopens into a cylindrical chamber 44 in which is located a cylindrical steel plug 45 abutting the screw plug 4|.

we provide a tapered anvil member 41 which fits the upper part of the conical bore 43 and extends part way into the cylindrical cavity 44. We further provide a tapered mold liner 49, which fits the conical bore 43 just below the anvil member 41. The anvil member 41 preferably has a cylindrical projection 59 on the bottom thereof, which fits a counter-bore 5| at the top of the liner 49, thus to provide a good seal between these parts. The anvil member 41 and the mold liner 49 may be made of steel, such as a good grade of tool steel. The liner 49 is in a real sense itself a mold.

Referring to Figures 1 and 2, the liner 49 has a cylindrical bore 52 extending through it from end to end. The ram or piston l5 fits in this bore 52, and on the upper end of the ram or piston 15, when it is in the bore 52, is a soft. steel sealing plate 53 having on its upper side an interiorly tapered annular projection 54. Similarly, under the cylindrical projection 56 of theanvil member 41 is a soft steel sealing plate 56 having an interiorly tapered annular projection 51. The heating charge, the insulation and the specimen are placed in the chamber formed by the bore 52 and the sealing plates 53 and 56, and are therein subjected to pressure. The pressure is transmitted from the ram 30 via the head 3i, the removable blocks 25, the head 20, the block 16 and the piston to the sealing plate 53, then through the charge, insulation and specimen to the sealing plate 56, thence to the anvil member 41, the plug 45, the screw plug 4| to the cavity block 12, which transmits the thrust to the plates lllwhich are held down by a massive iron cap 24 which is a permanent part of the hydraulic press.

In accordance with the invention we provide a suitable heating charge, which will heat the specimen while it is under pressure, and we provide suitable means to ignite this charge. Desirably, we provide a detonator, an igniter and a main charge. We will describe the best combina ion now known to use, but it should be understood that other chemicals may be employed so far as the broad aspects of the inyention are concerned. A suitable detonator is tetracene. This is understood to have the following structure:

NO N-CH:

Ha N01 N02 This detonator reacts upon impact and produces an intense heat which ignites the igniter. As will hereinafter be described, we provide means to set off the detonator upon the attainment of a certain pressure.

The igniter which we have successfully used is a combination of two mixtures. The mixture nearest the detonator was sugar and potassium chlorate, KClOa, the sugar was sucrose. The sugar and the potassium chlorate were mixed in stoichiometric proportions according to the reaction,

The second igniter mixture which was placed next to the first igniter mixture was magnesium and sodium peroxide. These were mixed in stoichiometric proportions according to thereaction The proportion of the igniter mixtures was .080 part of the first and .350 part of the second. The main charge reacted according to the following formulae:

(1) Mg+Na2O2=MgO+Na2O (2) 3Mg+KClOs=3MgO+KCl However, stoichiometric proportions were not used, rather, the following proportions were found to give good results:

P81 cent NazOz 19.1 KClOa 42.3 Mg 38.6

it being understood that the addition of MgO lowers the temperature.

Referring now to Figures 2 and 3, extending between the sealing plates 53 and 56 was a cylindrical graphite casing 60 having a cylindrical chamber 6| opening to the upper side, the easing being bevelled at bottom and top to fit the annular projections 54 and 51. This graphite casing 66 was of course crushable under the high pressure employed, but would stay more or less in position and constituted refractory insulation. Inside and at the upper end of the graphite casing 60 was a graphite plug 62 having an axial bore 63. Plugging the upper end of axial bore 63 was a graphite plug 64. Under the graphite plug 64 was a steel plug 65 fitting the bore 63, the steel plug 65' having a cylindrical projection 66 fitting a counterbore 61 in a steel container 68, also fitting the bore 63. This steel container 68 had a tapered axial bore 69, the large end being up, and the small end opening into a wide cylindrical chamber 19 at the bottom of the container 66.

The tetracene in granular form is shown at 1| in the bore 69, not quite filling the bore, but leaving an air space 12 above it. ,The bottom of the bore 69 was closed by a hardened steel disc 15 of a diameter the same as that of the chamber 10, but of lesser thickness except for the central portion where an integral projection or button 16 fills the chamber 16. Under the container 68 and under the button 16 was a layer of powdered graphite 11 having the shape of ,a disc. Below the graphite layer 11 was the first igniter mixture 18, also in the form of a disc. Under the first igniter mixture NaNs' or tetra nitro guanidine.

" ture 19, more or The mixtures "I8 and I9 were loose mixtures and theboundaries were not exact, and some intermixture occurred.

Under the second igniter mixture 19 was a graphite container 80 having an axial bore 8| opening at the bottom of the container 80. Under the container 80 and blocking the bore 8| was a molybdenum disc 82. The lower part of the steel container 68 plus the graphite I1 and the mixture 18, the mixture 19 and'the graphite container 80 and the molybdenum disc 82, were all contained in a straight cylindrical bore 85 in the main charge 86, which filled the bore 6| under the plug 62, all as clearly shown in the drawings, Figures 2 and 3. The main charge was molded and pressed to the shape shown, and had enough strength to hold together while being filled with the materials and parts described. In the bore 8| the-specimen 9|! was surrounded by powdered graphite 9| The purpose of the apparatus is to subject the specimen 90 to great heat and pressure simultaneously. Once the parts and mixtures are assembled as described, the pressureis applied whenever the main ram 30 exerts the desired thrust, which is accomplished by manipulation of the controls of the press, not shown. As soon as the pressure reaches a certain value, the charges are ignited and the specimen 90 is heated. This occurs in the following manner.

The pressure between the sealing plates 53 and 56 compresses everything between them, but the pressure on the button 16 is unsupported on the-upper side due to the space 12. Finally, therefore, the disc 15 shears and the button 16 shoots like a bullet into the tetracene detonator ll. This sets off the detonator, whichfiashes back through the graphite l1 and into the first igniter charge 18. This charge 18 ignites and heats the main charge 86 and also sets ofi the second igniter charge 19. The two charges.l8 and 19 together set off the main charge 86, which provides intense heat to the required temperature. This temperature is maintained for a considerable time, due to the fact that it is developed entirely inside of an envelope of graphite. For that reason it does not melt the steel parts. Gradually, of course, the heat is dissipated, but the pressure can be maintained from the moment the tetracene is ignited right through the heating cycle, and in fact for an indefinite period.

In practice the pressure has been maintained for usually about 5 minutes, sometimes longer.

The detonator may be other than tetracene, the igniter may be difierent and the main charge may be different. For example, the detonator might be mercury fulminate, or sodium azide Many nitrated organic compounds might be used. A detonator should be sensitive and it should produce a powerful shock. We consider that picric acid is the borderline case with regard to sensitivity and our detonator should be at least as readily detonated as picric acid. Explosive chemists can measure thesensitivity of detonators.

With regard to the shock producing properties we define our detonator as one which produces gas. By gas we mean anything which is a gas at just above 100 C. 'or at 100 C. and somewhat less than 30'. of mercury. Water is a gas under these conditions.

In some cases the igniter charge might be omitted and the main charge be fired by the detonator. However for the most reliable results we prefer to have an igniter and it will be noted that in the illustrative embodiment of the invention a two stage igniter was provided.

It will be seen that the main charge comprises, and in fact in the illustrative embodiment mainly consists of, an elemental metal and'a substance containing combined oxygen. In the illustrative embodiment magnesium is the element and sodium peroxide and potassium chlorate are the compounds containing oxygen. The elements magnesium, aluminum, lithium, calcium, strontium and barium have oxides which have a high heat of formation. The elemental metal which may be referred to as an element should be selected from this group. The oxygen containing compound'should be an oxidizing agent and may be defined as a compound or compounds whose oxygen is as easily detached as the oxygen of iron oxide FeO. A mixture of aluminum and iron oxide when ignited gives ofi intense heat and is known as Thermite. It will be noticed that in the illustrative embodiment the reaction of the main charge does not produce gas as above defined. It will be noticed on the other hand that one of the igniter mixtures reacts to produce gas. This is the mixture of potassium chlorate and sugar. The other or second igniter mixture is seen to be identical with one part of the main charge and from a chemical standpoint may be considered as part thereof.

It has been pointed out that the plates l0 act as a reinforcement of the cavity block l2 due to the tapered outer surface of the latter and the thrust against it from the large end of the taper. The reverse taper of the bore of the cavity block permits the mold liner 49 and anvil member 41, to be readily withdrawn from the cavity block l2 even after the ram l5 has exerted an enormous thrust equivalent to 30,000 atmospheres or more. We have ,found that a large screw plug 4| of the type shown and described can be tightened sufliciently to hold the mold parts in place under these conditions of high pressure. One feature which permits the cavity block l2 to withstand the high tensile force is the comparatively long dimension of the cavity block from the anvil member 61 to the plug Al.

The sealing plates 53 and 56 made of soft steel effectively confine the charges and the specimen between them since the annular projections 54 and 51 try to expand under the pressure. The taper of the bore 69 allows the button 16 to move like a bullet in the bore once the disc 15 has sheared oil. This insures detonation. The molybdenum disc 82 was provided as a check on the temperature reached and in many of the experiments the molybdenum melted partially. Molybdenum has a melting point of 2620 C. at ordinary pressures and we believe that the melting point under these high pressures is not a great deal higher.

It will be seen from Figure 2 that the various charges and the specimen are all enclosed in graphite so that the heat persists for a reasonably long time. Probably if the temperature at the time of reaction is 2700 C. it does not drop below 2000 C. for a minute.

The apparatus and method of the invention can be used to study polymorphism and for experiments in geophysical research. It can also be used to change the state of matter where that can be done with heat and pressure of the order indicated.

It will thus be seen that there has been provided by this invention a method and an apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. A mold for high pressure high temperatureattainment comprising}; cavity block with an exterior conical surface and a conical bore, the taper of the surface being opposite to that of the bore, means to plug the bore at the large end, a liner fitting the bore and having a cylindrical bore, a pair of sealing plates in said cylindrical bore, charges including a detonator and a main charge in said cylindrical bore between said sealin plates, and a shearable element adjacent the detonator which will fire it when great pressure is exerted between said sealing plates.

2. Apparatus of the class described comprising a cavity block having an exterior conical surface and a conical bore, the taper of the surface being opposite to that of the bore, there being a cylindrical bore in the cavity block beyond the large the liner, whereby simultaneously to produce high heat and pressure when said charge is ignited and said ram exerts pressure.

3. In apparatus claimed in claim 2, the combination with the parts and features therein specified, of a detonating charge in the cavity block and a shearable element to set oil the detonating charge responsive to pressure exerted by the ram.

4. In apparatus of ,the class described, a mold liner having a cylindrical bore, a pair of sealing plates in said bore, and in said bore between said sealing plates the following: a detonating charge, a shearable element adjacent the detonating charge and so situated that when it is sheared by pressure part of it will hit the detonating charge, and an exothermic charge, whereby pressure in said bore between the sealing plates shears the element which sets off the detonating charge which sets off the exothermic charge thus heating a specimen which may have been placed between the sealing plates.

5. In apparatus for coincidentally heating a specimen and subjecting it to high pressure, a

mold having a bore, nieans blocking one end of the bore, a piston ram fitting the bore, a mass of refractory material in the bore said mass having a cavity, and in the cavity the following: a shearable element, a detonating charge adjacent the shearable element in such position that when the element is sheared part of it hits the detonating charge, an igniter charge adjacent the detonating charge, and a main exothermic charge adjacent the igniter charge, whereby when the piston ram exerts high pressure in the bore of the mold the element is sheared, the detonating charge is set off, the igniter charge is set oif and the exothermic charge creates intense heat coincidentally with the pressure while the refractory material retards cooling.

6. 'In apparatus for coincidentally heating a specimen and subjecting it to high pressure, a.

mold having a bore, means blocking one end of the bore, a piston ram fitting the bore, and in the bore the following: a shearable element, a detonating charge adjacent the shearable element in such position that when the element is sheared part of it hits the detonating charge, an igniter charge adjacent the detonating charge, and a main exothermic charge adjacent the igniter charge, whereby when the piston ram exerts high pressure in the bore of the'mold the element is sheared, the detonatingcharge is set off, the igniter charge is set off and the exothermic charge creates intense heat coincidentally with the pressure.

PERCY W. BRIDGMAN.

SAMUEL S. KISTLER.

WILLIAM MAXWELL WHEILDON, JR.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Jones: Inorganic Chemistry, Blakiston Co., 1947, p. 259. y

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