US2938998A

US2938998A - High pressure dies

Info

Publication number: US2938998A
Application number: US804057A
Authority: US
Inventors: Wendell B Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-04-03
Filing date: 1959-04-03
Publication date: 1960-05-31
Anticipated expiration: 1977-05-31

Description

May 31, 1960 w. B. WILSON 2,938,998

HIGH PRESSURE DIES Filed April 3, 1959 r INVENTOR. Mendel! ,8. 11117501:

and heating a specimen.

Unite HIGH PRESSURE DlES Filed Apr. 3, 1959, 591'. No. 804,057

7 Claims. (31. 219-149 This invention relates to an apparatus for compressing More specifically, the invention relates to an arrangement of cooperating pressure dies and a heater used therewith for acting on certain materials being studied for the effects that high pressures and elevated temperatures have upon them.

It has been found desirable to study the eifects of high pressures and elevated temperatures on certain materials such as bismuth, urania (U yttria (Y O and thoria (ThO particularly when the high pressures and elevated temperatures are maintained for relatively long times. One drawback with known apparatuses for these purposes is that it has been impossible to subject a material being studied to very high temperature and very high pressure at the same time, though these conditions might be obtained separately. Another drawback has been that die materials hard or inelastic enough to obtain high pressures would break with certain stresses.

An object of the present invention is to provide an apparatus that will subject a specimen to high pressure and elevated temperature simultaneously. In the present apparatus a heater is contained within a die chamber and the die parts are protected from the weakening effects of the elevated temperatures to which the material under study is subjected.

A further object is to provide support and protection for hard pressure dies which prevent these dies from being broken without interfering with their ability to produce high pressure through reduction in size of the die space.

Other objects will appear from the description and the drawings in which:

Fig. 1 is a sectional view of the novel apparatus of the present invention;

Fig.2 is a sectional view, similar to Fig. 1, of the portion of the apparatus contained in the circle 2 in Fig. 1;

Fig. 3 is a diagrammatic view of the portion of the apparatus in Fig. 2, showing volume changes produced by the apparatus; and

Fig. 4 is a diagrammatic view showing the portion contained in the circle 4 in Fig. 3.

As shown in Figs. 1 and 2, the apparatus of the present invention comprises upper and

lower male dies

20 and 21, a female die 22 receiving the male dies, an electrically insulating layer 23 between the

dies

20 and 22, an electrically nonconducting thermal insulator 24 in the die space, a resistance-heater tube 25 within the thermal insulator 24, and thermally-insulating plugs 26 fitting within the ends of the tube 25. The tube 25 and plugs 26 enclose a sample or specimen 27 to be pressed and heated.

The heater tube 25, which is formed of graphite, or a metal such as tungsten, nickel or platinum, is needed if the specimen 27 is a nonconductor or poor conductor such as uram'a or yttria or is a conductor only at high temperatures such as thoria. When a graphite heater is used it is necessary to line the heater with a material such as beryllia, BeO, to allow study of oxide systems.

atent O "we 2938998 Patented May 31, 1960 If this is not done, the graphite will react with the oxide sample. The beryllia lining 27a terminates short of the ends of the heater tube 25, so that the plugs 26 will contact the interior of the heater tube at or near its ends. If the specimen 27 is a good conductor such as bismuth, the specimen constitutes its own electrical-resistance heater, and neither tube 25 nor plugs 26 are needed. The thermal insulator 24 is formed of silver chloride or unfired pyrophyllite such as Al O .4 SiO .H O or unfired steatite such as 3 MgO.4 SiO H O. Plugs 26 may be formed, for example, of a thermallyinsulating material such as nickel, pyrophyllite or steatite.

The male dies 20 and 21 are formed of a very hard material such as tungsten carbide cemented by cobalt, for example, 6 w/o. The female die 22 is formed of a somewhat softer material such as 4340 or 4140 SAE steel having a Rockwell hardness of 60-62. The male dies 20 and 21 have frustoconical portions 28 which fit frustoeonical recesses 29 formed in the female die 22. The recesses 29 are axially aligned and are connected by a circular cylindrical recess 30 aligned therewith, in

which the thermal insulator 24 fits.

The male dies 20 and 21 are mounted, respectively, in a head 31 and a base 32, which may be of steel, by means of backing members 33 and sleeves 34, which are press-fitted or shrink-fitted on the male dies and are formed of 4340 or 4140 SAE steel having a Rockwell hardness of 60 62. The backing members 33 have a hardness comparable with that of the male dies 20 and 21 and so may be formed of tungsten carbide cemented with 6 w/o cobalt. The backing members are of appreciably greater diameter than the male dies 20 and 21 and so distribute the end thrust of the

dies

20 and 21 over wider areas of the head 31 and base 32, with less tendency of these parts to distort because of being softer than the backing members 33. The sleeves 34, which are threaded in the head 31 and base 32 and carry the backing members 33 and dies 20 and 21, provide circumferential support to the

dies

20 and 21 and so lessen their tendency to fracture under shear.

The female die 22, which is slightly smaller in outer diameter at its bottom than at its top, is pressed in an inner binding ring 35, which is smaller in inner and outer diameters at its bottom than its top. The inner binding ring 35, whch may be formed of 4340 or 4140 SAE steel having a Rockwell hardness of 48-52, is pressed in an outer binding ring 36, which may be formed of the same steel having a Rockwell hardness of 32-36. The ring 36 is smaller in inner diameter at its bottom than its top and is pressed in a safety ring 37, which may be formed of mild steel.

An annular shield 38 rests on the ring 36 and protects against flying pieces that would result if the upper male die 20 fractured. An annular wall 39 is provided to contain cooling water around the lower male die 21 and its sleeve 34. The wall 39 carries in grooves in its upper and lower edges, O-ring seals 40, which are pressed against the outer binding ring 36 and the base 3'2. The wall 39 and the water contained therein will protect against possible shattering of the lower male die 21.

The insulating layer 23 between the upper male die 20 and the female die 22 is preferably of Fe O in the form of rouge painted on both the trustoconical portion 28 of the upper die 20 and the upper frustoconical recess in the female die 22. The layer 23 is thick enough to enable thermocouples to be brought out of the sample 27 through the layer. The frictional properties of Fe O of which the layer is formed, prevent the thermal insulator 24 from being squeezed out between the upper male die 20 and the female die 22. The frustoconical portion 28 of the lower male die 21 is lubricated so spasms that, as the male dies and 21 move toward one another, the female die 22 is expanded.

At the start of the operation, when upper male die 20 is elevated from the position of Fig. l, the thermal insulator 24 is fitted into the cylindrical recess 30 in the female die 22, the heater tube 25 is inserted in the insulator 24, the lower plug 26 is put in the heater tube 25, the specimen 27 is inserted therein, and the upper plug 26 is placed in the tube 25 on top of the specimen 27. The preliminary over-all height of this assembly of insulator 24, heater tube 25, end plugs 26, and specimen 27 may be a little greater than the length of the cylindrical recess 30, so that the specimen 27 may be preliminarily compressed when the frustoconical portion 28 of the upper die is brought into engagement with the upper frustoconical recess 29 of the female die 22.

. Additional downward force is applied to the upper male die 20 to move it closer to the lower male die 21. This is possible, because the female die 22, being of steel, has appreciable elasticity and can expand. It is necessary to relate the height of the cylindrical recess 30, or the assembly of insulator 24-, heater 25, plugs 26, and specimen, the radius thereof, and the angle of the frustoconical die portions 28 to one another in such a way that the decrease in volume due to contraction in height is greater than the increase in volume due to increase in radius. Reference is made to Fig. 3, wherein the fulllines show the die positions before the female die 22 is expanded, the dotted-lines show the die positions after the female die is expanded, and the hatched areas show the volume changes. Thus, the volume decrease due to height contraction is ZAh'yr and the volume increasedue to radius expansion is approximately Z'yrhAr. Since the volume decrease must be greater than the volume increase for the sake of pressure increase, 2Ah'yr Z'yrhAr or r/h Ar/Ah. Since, as seen from Fig. 4, the relation of the increase in radius to the decrease in height is related to the angle the frustoconical portions 28 make with their axes, as expressed by the equation Ar/Ah: tan 0, by substitution it is seen that it is necessary for r/h tan 6.

On this basis, satisfactory results were obtained with r=.25", 11:25," and 6:35". The preliminary height of the assembly of insulator 24, heater tube 25, plugs 26, and specimen 27 was .31". As the male die 20 is pushed into recesses 29 in female die 22, the excess height of the sample is crushed into the die bore which serves to compact the sample and eliminate voids.

The size of the heater tube 25 may be varied from to over For example, a thin-walled platinum tube A3" in diameter may be used as may a graphite tube varying from /s" to The wall thickness of the heater tube is not important since this aifects only the power required to obtain a given temperature.

Electric current is supplied to the heater tube 25 through the male dies 20 and 21 and is forced to go through the heater-tube 25 because of the insulating layer 23 between the upper male die 20 and the female die 22. Since the heater tube 25 lies within the thermal insulator 24, the female die 22 is thermally shielded and is not weakened by heating. The plugs 26 prevent the specimen 27 while being compressed from flashing out over either end of the heater tube 25 and the male dies 20 and 21. Pressures in excess of 110,000 atm. have been obtained with an applied force of 225 tons. The theoretical maximum is about 200,000 atmospheres.

With the die arrangement of the present invention, the advantage of the die space of right-cylindrical shape is kept, namely, the ability to reduce volume and thus increase pressure. Yet the dies 20 and 21, which are extremely hard and likely to fracture in shear, are supported by the die 22 so as to be protected from fracture. Likewise the die 22 is supported against fracture by binding ring 35. The frustoconical portions 28 of the dies 20 and 21 and the frustoconical recesses 29 in the 4 die 22 receiving them provide the dies 20 and 21 with support against fracture while permitting them to reduce the height of the die space afforded by the recess 30 in the die 22. Proper proportioniing of parts makes reduction of volume possible through height reduction in spite of radius increase of the recess 30 due to supporting the dies 20 and 21 against fracture while they move toward one another. The frustoconical shaping of the die parts recesses being shaped to receive the frustoconical male dies, an annular cylindrical thermal insulator fitting within the cylindrical middle portion of the opening in the female die, an electrically conducting tube fitting within the thermal insulator and having its ends in electrical contact with the male dies, and short thermally insulating plugs fitting within the ends of the tube so as to be adapted to cooperate with the tube in containing the specimen within the tube and between the end plugs, one male die being electrically insulated from the female die by a layer of Fe O rouge between said one male die and the frustoconical recess in the female die mating therewith.

2. The apparatus specified in claim 1, the female die being of steel having a Rockwell hardness of 60-62, the male dies having 6% cobalt, the electrically conducting tube being of platinum, the thermal insulator being of pyrophyllite or steatite, the plugs in the tube being of nickel.

3. Apparatus for exerting very high pressures on a specimen and simultaneously heating it, said apparatus comprising a plurality of cooperating male and female dies of electrically conducting material fitted together to enclose a cylindrical space, an annular cylindrical thermal insulator occupying the radially outermost portion of the space, an electrically conducting tube fitting within the thermal insulator and having its ends in electrical contact with the male dies, and short thermallyinsulating plugs fitting Within the ends of the tube so as to be adapted to cooperate with the tube in containing the specimen within the tube and between the end plugs, one die being electrically insulated from another of the contacting it by a layer of Fe O applied between these two dies.

4. The apparatus of claim 3, the electrically conducting tube being of graphite having a beryllia lining, and the thermal insulator and the plugs being of pyrophyllite or steatite.

5. The apparatus of claim 3, the electrically conducting tube being of platinum, the thermal insulator being of pyrophyllite or steatite, the plugs in the tube being of nickel. v

6. Apparatus for exerting very high pressures on a specimen, comprising male dies of tungsten carbide having frustoconical surfaces, and a steel female die having aligned frustoconical recesses joined by a circular cylindrical recess, the frustoconical recesses being shaped to engage the frustoconical surfaces of the male dies, the ratio of the height of the cylindrical recess to its radius being greater than the tangent of the angle made by the frustoconical surface of each rnale die with its axis.

7. Apparatus for exerting very high pressures on a specimen and simultaneously heating it, said apparatus comprising a plurality of cooperating male and female dies of electrically conducting material fitted together to enclose a space, an annular thermal insulator occupying the radially outermost portion of the space, and an 5 electrically conducting tube fitting within the thermal insulator and having its ends in electrical contact with the male dies, the tube being adapted to contain the specimen, one die being electrically insulated from another of the dies contacting it by a layer of F6 0 between these two dies.

References Cited in the file of this patent UNITED STATES PATENTS