IE41418B1

IE41418B1 - High pressure apparatus

Info

Publication number: IE41418B1
Application number: IE1239/75A
Authority: IE
Original assignee: Scandiamant Ab
Priority date: 1974-06-06
Filing date: 1975-06-03
Publication date: 1980-01-02
Also published as: JPS515678A; CH613635A5; ZA753633B; DE2523068C3; CA1049720A; IE41418L; FR2279990A1; SE7407437L; NL7506241A; IT1036181B; DE2523068B2; FI57703C; BE829864A; AU8175575A; SE382159B; FI57703B; DE2523068A1; GB1485907A; FI751678A; FR2279990B1

Abstract

A pressure chamber (10) is located between two opposite pressure-proof bodies (11, 12), at least one of which can be moved towards the pressure chamber (10). The pressure chamber (10) boundary wall located between the pressure-proof bodies (11, 12) is formed by the inner walls of the holes (15-19), which are aligned with respect to one another, of a plurality of pressure-proof disks (20-24) which are stacked on top of one another in the direction of movement of the pressure-proof body, a seal (25-28) being disposed between at least one pair of adjacent disks. In order to ensure that the pressure chamber (10), if the pressure-proof bodies (11, 12) move, is likewise shortened and the pressure distribution in the material (95) positioned in the pressure chamber (10) thus remains uniform, the seal (25-28) is made of a compressible material, for example of pyrophyllite. The high-pressure press can be used to convert graphite into diamond.

Description

Known apparatus for generating very high pressures, e.g, apparatus for conversion of graphite to diamond, have pressure chambers of relatively small volumes. It has long been desirable to achieve high pressure apparatus with a greater volume of the pressure chamber since such apparatus would re5 suit in increased capacity. One reason why it has been impossible to realize this desire is the frictional forces generated between the material enclosed in the pressure chamber and the walls of the pressure chamber, as well as in the material itself, when the material is subjected to compression. The frictional forces cause the pressure to decrease successively in a direction ιοί 0 wards the interior of the material and therefore limit the thickness in the direction of compression of the material within whioh it is possible everywhere to attain a certain desirable minimum pressure, i.e. limit the height of the pressure chamber if the compression is assumed to take place in a vertical dire'ction. If a considerably larger volume of the pressure chamber is attempted, by increasing its area perpendicular to the direction of compression, other problems are encountered. One problem is that the forces which would then be required, to generate the pressure are so great that they cannot be overcome under practical conditions. Another problem is that there are no possibilities of manufacturing components for the parts of the high pressure apparatus located nearest the pressure chamber. These components, for example parts of cemented carbide, would be too large to be able to be manufactured with sufficient strength. Regardless of how the pressure is generated the necessary gaskets must be dimensioned so as to prevent the - la 41418 material from flowing out of the pressure chamber. Thie requirement limits the thickness of the gaskets.

A high pressure apparatus which is well-known among experts and which has been used when manufacturing diamonds on a commercial scale is described in the United States Patent Specification No. 2,941,248. The apparatus comprises a pair of opposed punches and a die arranged between them with a oentral throughgoing hole. The two openings of the hole are formed with outwardly increasing cross-sections and each punch with an inwardly decreasing cross-section in a corresponding manner, so that the punches may be inserted into the hole to a certain depth, between eaoh opening of the hole of the die and each punch there is arranged a gasket which seals the pressure chamber formed of the punches and the hole of the die. This high pressure apparatus, which must be dimensioned for each specifio application, has a pressure chamber with a relatively small volume. A modification of the apparatus to increase the volume of the pressure chamber would cause the problems described above.

The present invention makes it possible to construct high pressure apparatus having pressure chambers with considerably larger volumes than in previously known high pressure apparatus. The new high pressure apparatus is of the kind having a pair of opposed punches or similar opposed members, at least one of them being movable to achieve a compression in its direction of movement of the material enoloeed in the pressure chamber. Not least because of their simplicity, high pressure apparatus of this type have proved to possess considerable advantages under conditions in practice. The larger volume of the pressure chamber is achieved according to the invention by con25 structing the pressujg. i^pjeB§tffe1chamber between the opposed members of several pressure-resisting elements arranged one after the other in the direction of compression, at least one compressible gasket being arranged between said elements, by this arrangement pressure is conveyed to the enoloeed material at various levels in the pressure chamber when the movable member or 3o members move, thus largely eliminating the limitation imposed by the friotional forces on the compression of the material - in the direction of . compression, as mentioned above. The possibility of increasing change in axial length of the .pressure chamber'fn the direction of the compression in apparatus according to the invention, makes it possible to inorea35 se the volume of the pressure chamber without having to make the parts of cemented carbide or other components nearest the pressure chamber so large that they cannot be made with sufficient strength. -241418 According to the invention high pressure apparatus comprising a pressure chamber formed of a pair of opposed pressure resisting members, at least one of them being movable in a direction towards the interior of the pressure chamber, a pressure-resisting chamber wall located between these members, the chamber wall comprising the bores of aligned holes in a plurality of pressure-resisting1 disc members arranged one after the other in the direction of movement of the movable member and a layer of separating material between at least one pair of adjacent disc members is characterised in that the separating material is a gasket made of a compressible material, so that on application of pressure the distance between the terminal disc members is decreased by compression of the at least ene gasket When the invention is utilized to its optimum a compressible gasket is placed between each pair of adjacent disc members.

According to a preferred embodiment of the invention, in at least one of the disc members which are located nearest to the opposed members, at least the part of the hole facing the adjacent opposed member is formed with an outwardly increasing cross-section, and the part of the adjacent opposed member facing the hole is formed with an inwardly decreasing cross-section in a corresponding manner, and a compressible gasket is placed between, the corresponding shaped opposed members.

Apart from the fact that the gaskets (or gasket) between the disc members should be compressible to allow a displacing movement of the disc members towards each other in the direction of movement of the movable opposed member or members, they should be able to maintain a firm grip on to the surfaces against which they bear during the whole working procedure in the high pressure apparatus. Suitable materials in the gasket are, e.g. pyrophyllite, talc, pot stone, satlinite, lithographic stone and hexagonal boron nitride. The gasket may be strengthened by metal inserts to increase their toughness and ductility, or be provided with supporting rings to prevent or counteract radial blowing-out. If gaskets are used between the opposed pressure-resisting members and the adjacent disc members and are made compressible, they may be made of materials of the same type as the other gasket(s) and may also incorporate strengthening metal inserts.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 shows a high pressure apparatus according to the present invention in a section in the direction of compression, and Figure 2 shows a disc member in the high pressure apparatus according to Figure 1, seen from above.

In the high pressure apparatus according to Figure 1 the pressure chamber 10, which is cylindrical, is limited at its end surfaces by pressure-resisting members in the form of punches 11 and 12 which are movable in a direction towards the interior of the pressure chamber (i.e. in the axial direction of the cylindrical chamber). The movement is brought about by the partly shown pistons 100 and 101 in a hydraulic press acting on the outsides of the pressure plates 13 and 14 - bearing against the punches - of, e:g. highspeed steel hardened to 60 RC. The pistons 100 and 101 are electrically insulated from the pressure plates by insulating layers 102 and 103, respectively, of phenolic resin paper laminate. The pressure chamber is limited in the radial direction by a pressure-resisting chamber wall defined by the bores of the cylindrical holes 15, 16, 17, and 19 of several pressure-resisting and pressureabsorbing disc members 20, 21, 22, 23 and 24 and by compressible annular flat gaskets 25, 26, 27 and 28 of, e.g., pyrophyl1ite, arranged between the disc members. In the illustrated embodiment the gaskets are provided in the middle with metal inserts which are parallel to the contact surfaces of the gaskets with the disc members but these are not thought to be essential. As is clear from the figure, the disc members are arranged one after the other in the direction of movement of the punches, the holes therein being aligned. The gaskets keep the disc members spaced from each other so that gaps 29, 30, 31 and 32 are formed between them. In the disc members 20 and 24, which are located nearest the punches, the holes of the parts 33 and located nearest the punches are formed with outwardly increasing cross-section. In the exemplified case said holes are frusto-conical. The parts 35 and 36 of the punches 11 and 12 which are facing and located nearest the pressure chamber have a correspondingly inwardly decreasing cross-section, i.e. they are frusto-conical in the exemplified case. Between parts 33 and 35 and between parts 34 and 36, respectively, there are arranged compressible gaskets 37 and 38, for example of pyrophyl1ite. In the illustrated embodiment these gaskets are also provided with metal inserts which are parallel to the contact surfaces of the gaskets with the parts 33 and 35 and 34 and 36, respectively, but again the provision of such inserts may not be essential.

The shape of the gaskets is adjusted to the shape of said parts, which means that they are frusto-conical in the exemplified case. The disc members are provided with guide members which ensure that the disc members are not displaced in a lateral direction or are obliquely positioned in relation to each other when the pressure is built up and maintained in the high pressure apparatus. The guide members, which may be constructed in various ways, consist in the illustrated embodiment of resilient flanges 39, 40, and 42 and 43, 44, 45 and 46 respectively, running along the periphery of the disc members and these co-operating in pairs. Thus, as shown, a flange, e.g. 39, in a disc member is supported by a flange, e.g. 43, in an adjacent disc member, the lastmentioned flange having a support edge 43a for the flanoe 39. The support edges for the flanges 43, 44, 45 and 46 are designated 43a_, 44a_, 45a and 46a respectively.

Another way of making the guide members is to make the parts 39, 40, 41 and 42, the substantially horizontal portions of the parts 43, 44, 45 and 46 and the parts 43a, 44^, 45a and 46^ as separate loose parts, each of which in the two first5 mentioned groups of parts bears inwardly against a supporting edge on the corresponding ring 31, 82, 83, 84 or 85 described later on, and bears outwardly on a separate loose ring, which corresponds to each of the parts 43^ - 46a, Each punch 11 and 12, respectively, has central part 47 (which forms one whole continuous unit with the part 35) and 48 (which forms one whole continuous unit with the part 36) of cemented carbide, for example consisting of 94% VIC and 6% Co. Concentric backing or binding rings 49, 50, 51 and 52, 53 and 54, respectively, of tool steel hardened to a hardness of 52-54 RC are shrunk onto the respective central parts in a known manner. The fitting surface may be slightly frusto-conical to facilitate the shrinking on. The task of the binding rings is to provide support pressure for the central part 47 and 48, respectively, of the punch in order to increase its ability to withstand great radial and tangential stresses.

Each disc member 20 and 21, 22, 23 and 24, respectively, has a central ring 55 and 56, 57, 58 and 59, respect!vely, of cemented carbide, for example consisting of 90% WC and 10% Co. The rings are surrounded by sector-shaped discs 60 and 61, 62, 63 and 64, respectively, of cemented carbide, for example consisting of 85% WC and 15% Co, which are arranged with intermediate gaps 65 (see Figure 2 which shows the disc member 21). Around these discs concentric backing or binding rings 66, 67, 68 and 69, 70, 71 and 72, 73, 74 and 75, 76, 77 and 78, 79, 80, respectively, are shrunk on in conventional manner. The material in them is tool steel hardened to a hardness of 52-54 RC. The fitting surfaces may be slightly frusto-conical. The binding rings achieve a support pressure on the central rings through the sectorshaped discs. At their extreme ends the disc members are provided with outer rings 81 and 82, 83, 84 and 85, respectively, of tool steel hardened to a hardness of 45 RC, in which the previously mentioned resilient flanges 39 - 42 and 43 - 46 serving as guide members form integral parts in the case illustrated in the Figures. The guide members are formed so that they contribute to the support pressure on the central rings 55 - 59 by achieving a radially inwardlydirected pressure component.

In the pressure chamber a reaction element is arranged. It contains two discs 86 and 87, respectively, of electrically conducting material, e.g. steel, making contact with the punches, said discs having an inwardly protruding portion 88 and 89, respectively. A disc 90 and 91, respectively, of electrically conducting material, for example steel, makes contact with the respective inwardly protruding portion to define closed cylindrical spaces 92 and 93, respectively, which are formed of the portions 86, 88 and 90 and 87, 89 and 91, respectively, are filled up with a heat-insulating material, for example talc. Between the discs 86 and 87 and outside the cylindrical portions 88 and 89 and the discs 90 and 91, there extends an electrically insulating and heat-insulating tube 94, for example of pyrophyllite which contacts the pressure-resisting cylindrical wall of the chamber. Inside this tube and between the discs 90 and 91 there is arranged a material 95, which is to be exposed to pressure, in the exemplified case a reaction element consisting of graphite and nickel or other metal having the ability to dissolve carbon. By subjecting this reaction element to very high pressure and high temperature, the graphite can be converted to diamond. Heating is performed by electric current which is conducted through the reaction element between the punches through the portions 86, 88 and 90 and 87, 89 and 91, respectively. The connection conductors for the current which are arranged on the pressure plates 13 and 14 are designated 96 and 97. A reaction element comprising graphite and metal has sufficient electrical conductivity to be able to be directly subjected to electrical resistance heating. If the material 95 is of another kind, which does not have such a good electrical conductivity, the heating can be brought about by embedding tubes, discs, wires or other bodies of electric resistance material into the material 95 or arranging them around the material 95.

The material 95 may be exposed to pressure by the pistons 100 and 101 in the hydraulic press, which achieve a displacement of the pressure plates 13 and 14 and the punches 11 and 12 towards each other. The movement of the punches takes place while compressing the gaskets 25, 26, 27 and 28 in the direction of movement of the punches, i.e. perpendicular to the contact surfaces of the gaskets with the disc members 20, 21, 22, 23 and 24. Also the gaskets 37 and 38 are compressed substantially perpendicularly to the contact surfaces with the adjacent members. When the gaskets are compressed a certain amount of flow of the gasket material takes place in a direction away from the pressure chamber. When the punches move, the material 95 is compressed. This compression takes place not only from the ends of the pressure chamber, but also at various levels in the pressure chamber by the described compression of the gaskets 25, 26, and 28. With the apparatus described, pressures of more than 50 000 atmospheres and simultaneously temperatures of more than 1 700°C can be achieved, i.e. pressures and temperatures which are usable for converting graphite to diamond.

In its simplest embodiment, the high pressure apparatus according to the invention only contains two disc members and only one compressible gasket located between the disc members. The high pressure apparatus shown in Figure 1 can thus be modified in such a way that the disc members 21, 22 and 23 may be omitted, as well as the gaskets 26, 27 and 28. The pressure-resisting wall of the pressure chamber 10 between the punches 11 and 12 is then defined by the bores of the holes 15 and 19 of the disc members 20 and 24 and of the compressible gasket 25.

Other embodiments of the invention are possible. Thus, the outer disc members may be constructed, for example, with openings without an outwardly increasing cross-section, the opposed pressure-resisting members then being suitably shaped as plane-parallel discs. Between these discs and the disc members located nearest thereto gaskets may be used which are similar in kind to the gaskets illustrated between the disc members, for example as the gasket 25. It would also be possible to use here non-compressible gaskets, for example gaskets in the form of steel rings, or to have no gaskets at all. Further, only one of the outer disc members, for example the member 24, may be shaped with an opening without an outwardly increasing cross-section, the opposed pressure-resisting member located nearest to this then being suitably shaped as a substantially plane-parallel disc which is sealed against the pressure chamber by a gasket of the same type as the gasket 25. It is also possible to use a non-compressible gasket of the previously exemplified kind, or to have no gasket at all. One of the opposed pressure-resisting members 11 and 12, whether it is formed as a punch with a portion having an inwardly decreasing cross-section according to Figure 1, or as a plane-parallel plate or in some other way, may also be stationary, for example resting on or consisting of a stationary press table.

Claims

1. What we claim is:1. High pressure apparatus comprising a pressure chamber formed of a pair of opposed pressure resisting members, at least one of them being movable in a direction towards the interior of the pressure chamber, a pressure-resisting chamber wall located between these members, the chamber wall comprising the bores of aligned holes in a plurality of pressure resisting disc members arranged one after the other in the direction of movement of the movable member and a layer of separating material between at least one pair of adjacent disc members, characterised in that the separating material is a gasket made of a compressible material, so that on application of pressure the distance between the terminal disc members is decreased by compression of the at least one gasket. ?. High pressure apparatus according to claim 1, in which a compressible gasket is placed between each pair of adjacent disc members.

2. 3. High pressure apparatus according to claim 1 or 2, in 5 which, in at least one of the disc members which are located nearest the opposed members, at least the part of the hole facing the adjacent opposed member is formed with an outwardly-increasing cross-section, the part of the adjacent opposed member facing the hole is formed with an inwardly 10 corresponding decreasing cross-section, and a compressible gasket is placed between the correspondingly shaped opposed members.

3. 4. High pressure apparatus according to any of claims 1 - 3, in which the compressible gasket between two adjacent disc members comprises pyrophyllite or talc. 15

4. 5. High pressure apparatus according to any of claims 1 - 4, in which the compressible gasket between two adjacent disc members incorporates a metal insert.

5. 6. High pressure apparatus according to any of claims 3-5, in which the gasket between an opposed member and a disc 20 member comprises pyrophyllite or talc.

6. 7. High pressure apparatus according to any of claims 3-6, in which the gasket between an opposed member and a disc member incorporates a metal insert.

7.

8. High pressure apparatus, constructed and arranged sub25 stantially as herein described with reference to, and as illustrated in, the accompanying drawing.