SE451951B - PROCEDURE FOR PREPARING A DIAMOND WIRE DISC PRESS body - Google Patents

Description

(FI ... à wD un ... S 2 the tension plate in a ring of metal with high strength and forming the wire drawing hole through the center of the poly- the crystalline diamond part using means which are well known to those skilled in the art, for example a laser. The hole can then completed by drawing a wire impregnated with mantle dust back and forth through the hole. The hole can be preformed during the sintering process at high pressure and high temperature, on the method of U.S. Pat. No. 3,831,428, column 4, lines 54-60 and figure 4 are followed (arranging in advance of a wire through the polycrystalline core, which then can be removed by dissolving in a suitable acid).

South African Published Patent Application 77/5521, Dietrich, describes a diamond filament press body provided with a tantalum cladding, which binds the carbide ring to the central polycrystalline diamond core. This patent application states that the tantalum layer effectively binds the diamond core to the the bite that surrounds it.

Wire pulley compacts both under U.S. Pat. U.S. Pat. No. 3,831,428 and the aforementioned South African publication according to Dietrich is produced by sintering process under high pressure and at high temperature, whereby a lytic metal, such as cobalt, infiltrates radially from it surrounding the metal carbide ring or cylinder (so-called sweeping process). This catalyst accelerates the sintering process and leads to comprehensive diamond-to-diamond binding. The quality of the diamond compact depends on the degree of diamond-to-diamond bonding in the microstructure. This binding- 7 seems to be achievable, when uniform and sufficient quantity cobalt is introduced into the grain boundaries under conditions including high pressure and high temperature, if other factors are taken into account constant.

The main problem in the production of compacts for traction board blanks with large size (eg diameter 24 mm) are insufficient diffusion of cobalt with conventional radial sweeping technique. Radial diffusion has been shown to be 451 951 3 insufficient to give the desired cobalt concentration in the whole diamond core.

The research that led to the present invention is performed to improve the diffusion of the catalyst into the traction sheave blanks of large dimension and to reduce the percentage defective substances obtained by known processes. Defects occurs mainly in the form of both poorly bound areas in the diamond core and cracking in the diamond or in the metal carbide parts. Cracking occurs unpredictably during different manufacturing operations, such as pressing, grinding outer diameter, surface grinding, lapping, as well as during conditions, which makes the detection of the cause very difficult difficult. Defects are also detected by X-ray radiographic investigation. Another purpose has been to apply one favorable method on traction sheave blanks of smaller size.

The above results have been achieved using axial catalyst diffusion at the high temperature / high pressure process together with the conventional radial sweeping method. The preferred method of axial cobalt diffusion provided with a layer of cobalt combined with a layer of refractory metal (for example molybdenum, tantalum or tungsten).

Addition of axial cobalt without a refractory metal is also one improvement over the tantalum cladding method according to Dietrich in some cases. With this method, position of traction sheave blanks of diamond compact with large dimensions (outer diameter 24.1 mm and inner diameter l2.0 mm) with more favorable yields than with previously known methods the new method gives a uniform concentration and adds sufficient amount of infiltrating cobalt.

The known process steps and parameters for producing diamond filament pulleys include that exposes a metal carbide cylinder by at least one holes, which extend through its thickness and join them both ends and is filled with a mass of diamond particles, for the following high pressure / high temperature sintering conditions: 451 951 4 A pressure of at least 50,000 MPa at a temperature of at least 1300 ° C in the diamond stable range, reaction time 10-90 minutes all of which are carried out in a high pressure reaction cell containing the diamond particles and the metal carbide in a screen mvlnllbeaker with on screen plate, which covers the open end of the beaker. The screen metal can be selected from zirconium, titanium, tantalum, tungsten and molybdenum metals. On one side of the metal carbide cylinder with diamond particles is arranged one plate containing diamond catalyst / solvent and solvent maintains the specified high pressure / high temperature sintering conditions until axial diffusion of the catalyst / solution the agent into the mass of diamond particles obtained.

The diamond stable range is the range of pressure / temperature conditions under which diamond is thermodynamically stable. IN a pressure-temperature phase diagram is the generally high-pressure side, above the equilibrium line between diamond and graphite.

Adjacent to the catalyst / solvent disc one can be arranged sheet of heat-resistant metal. Both discs can have one thickness of 25-l02; ¿m. Usually at least two discs are arranged one or more transition metals (for example zirconium, titanium, tantalum, tungsten or molybdenum) at the end of the metal carbide the cylinder with diamond particles opposite the side, on which catalyst / solvent disk is provided. These guided discs are suitably arranged inside the space which is formed of the shielded metal cup and disc.

A preferred form of high pressure / high temperature apparatus (although other such exist), in which the improved process according to the invention can be carried out, described in the U.S. Patent No. 2,941,248 (which forms part of landscape description) and is called a belt apparatus. This content takes a pair of opposing pistons of tungsten carbide cemented carbide and an intermediate belt or matrix portion of the same material.

The matrix part comprises an opening, in which one is arranged reaction vessel shaped to contain a charge unit or reaction cell. Between each press stamp and 451 951 5 the matrix there is a packing unit comprising a pair of heaters insulating and electrically non-conductive pyrophyllite parts and a intermediate metal gasket.

In a preferred embodiment, the reaction cell comprises a hollow salt cylinder. The cylinder can be made of anything other materials, such as talc, which (l) are not converted during high pressure / high temperature operation to a stronger, stiffer state (for example by phase transformation and / or compression) and (b) is substantially free of volume discontinuities that occur under the influence of high temperatures temperatures and high pressures, as occurs, for example, with pyrotropic filled and porous alumina. Materials that satisfy others criteria are set forth in U.S. Pat. No. 3,030,662 (column 1, line 59 to column 2, line 2, and what is indicated on this place forms part of the present description) and are useful for the manufacture of the cylinder.

Arranged concentrically in and next to the salt cylinder is one electric graphite resistance heating tube, which stretches past the salt cylinder at both ends. In graphite heating The cylindrical salt tube is concentrically arranged clothing. The ends of the cladding are fitted with salt plugs arranged at the top and bottom. The ends of graphite the heating pipe is internally provided with fitted pyro- filling plugs and externally with pyrophyllit rings, which are fills the space from the ends of the salt cylinder to the end of graphite heating tube.

Electrically conductive metal end plates were used at each end of the reaction cell to provide electrical connection to the graphite heating tube. Next to each metal end plate there is an end plate unit, each of which comprises one pyrophyllite plug or disc surrounded by an electrically conductive ring." Working methods for simultaneous impact of both high pressures and high temperatures in this type of apparatus are well known to those skilled in the art. 4-51 951 men in the super-high pressure field. The mission unit is in- fitted in the space formed by the salt coating and the salt the plugs and consists of a cylindrical sleeve of screen metal, in which one or more screen metal cups are arranged. The mass of diamond particles placed in the holes of the metal carbide cylinder may also contain graphite and up to 2.5% by weight of lysator / solvent. The mass of diamond particles is arranged in one or more cavities or holes through a disc made of cold-pressed sintered carbide powder (mixture of bite powder and suitable metal binder for this). If only a matrix is manufactured in each screen metal beaker, exists only such a hole which is usually concentric with metal carbide the discs that form a ring around the diamond core. If desired the ring or disc may be made of sintered metal. bonded carbide or fully sintered metal bonded carbide.

It is also possible to produce diamond wire drawing disc presses. bodies using only the axial diffusion technique.

A metal carbide that is free from catalyst metals (e.g. cobalt) can be used. In such a case comes radial solvent / catalyst permeation not to be effective but only the axial diffusion technique will influence.

The loading unit is inserted into the reaction vessel, which is applied in the high-pressure / high-temperature belt device. First, the pressure is raised and then the temperature and maintained at the desired conditions. for a sufficient period of time for sintering to fallow. The sample is then allowed to cool under pressure for a short time time (for example 3 minutes) and finally the pressure is lowered to atmospheric pressure (which may require about one minute) and the compact is recovered.

The screen metal sleeve can be removed manually. Possibly adhesive metal from the screen metal beaker or disc can sanded or licked away. Distortion or surface irregularity can be removed in the same way. 451 951 7 The metal carbide can be selected from tungsten, titanium or tan talc carbides and the material constituting metal binders in the metal-bonded carbide (binder) can be selected from the group consisting of cobalt, nickel, iron, chromium and mixed thereof. Cobalt-bound tungsten carbide is preferred.

The catalyst / solvent can be selected from the group consisting of cobalt, iron, nickel, ruthenium, rhodium, palladium, platinum, chromium, manganese, tantalum and mixtures of these materials.

Cobalt, iron and nickel are preferred, with cobalt in particular is preferred.

The heat resistant ("refractory") metals preferred for use for discs in the method according to the invention are molybdenum, tantalum, tungsten, zirconium and titanium.

Of transition metals, zirconium is preferred for use in transition metal sheets according to the invention.

A typical size range for diamond particles used as a starting material in the production of diamond compactors wire drawing boards are from 0.1 to 150fnm in largest dimension.

The finer sizes are preferred (0.1-45, pm) for discs such as was used for drawing wire, if a fine surface finish is required the thread.

Many experiments have been performed to optimize the number of different discs and their arrangements, as shown with the examples given in Table I below. In this table and hereinafter the term yield is defined as the number finished substances without defects divided by the total number pressed substances. The symbol used to illustrate make the design of the mission in the screen metal beaker repre- centers a cross-sectional sketch through a filled screen metal beaker.

In this, in reality, the different parts abut each other, but to make the picture clearer, the different parts are shown schematically at mutual intervals. 451 951 8. y - * - 'Zirconium screen metal plate --- Diamond particles Cobalt-bound tungsten carbide ring Zirconium screen metal beaker Preferably, the screen metal cup is crimped over the screen metal plate as indicated by the symbol above.

Table I.

Different sub-device configurations Configuration Exchange Process reliability ..._ MQ__ 40-60% Unpredictable and ___ Mo ___ unreliable .__ CO .__ EIEII] 50-70% Unpredictable UP IIEIEJ 90-100 Reliable and - CO - reproducible __MO __ F _ __Mo ._ __CO __ [31:12] 90-100 Reliable and __ZI __ reproducible .ízr __ Standard process 50-70% according to American the patent 3,831,428 451 951 9 The results in Table I are from high pressure / high temperature experiments. with the production of diamond filament press bodies with the following nominal dimensions: 13.7 mm outer diameter, 5.1 mm diamond core diameter and 3.8 mm thickness. Every discs used had a thickness of about 50 .mu.m. Best results obtained with configurations 3 and 4.

For matrices with larger diameters, it has proved suitable to use eight additional zirconium sheets on top (ie top of the molybdenum disk) and a total of eight zirconium disks on opposite side of metal carbide ~ and diamond massanf Another variation has also been used with good results: ..... MQ_ ..

CO EEE! CO This configuration differs from the subunit described above by having two catalyst / solvent disks used, one on each side of the metal carbide. The over- the metal of choice is also molybdenum instead of zirconium. and it is mounted outside the shielding metal the baker. In addition, molybdenum has been selected as a sheet of refractory metal and has been placed outside the plate of shielding metal.

The embodiment with the addition of one or more zirconium discs on the bottom inside the shielding metal cup have shown be optimal.

In the manufacture of wire mesh blanks has cracking in tungsten carbide in the press has been reduced from 5-20% (at tantalum cladding process) to 5-10% when using procedures it according to the invention and the total proportion of substances which cracks have been reduced from 30% to 20%. In addition, it can new process according to the invention is carried out for shorter periods 451 951 l0 time period (75 minutes under high pressure / high temperature conditions instead of the 90 minutes typical of tantalum clothing process), which leads to an increased production speed. Also the opening time has been significantly reduced. The knoop hardness of the diamond core of these large traction sheave compacts which produce is provided with the improved method according to the invention has been shown to be substantially equivalent to the hardness of compacts made by the tantalum cladding process.

In experiments with compacts with an outer diameter of 13.7 mm are shown Knoop hardness should be equal to or slightly lower than the of compacts produced by the process according to U.S. Patent 3,831,428, but the difference was not large enough to affect the use of the traction sheave properties. These experiments also reduced X-rays. the rejections from 10-30% to 5-10% and the cracking rate for substances outside the press was reduced from l5-35% to O-5%.

Promising results have also been obtained with smaller compacts (for example diamond core diameter 0.89 mm) from a replacement of 67% by the procedure of the U.S. patent 3,831,428 to 95% with axial cobalt diffusion.

Claims (10)

451 951 14 PATENT REQUIREMENTS A method of making a diamond wire drawing pulley, in which the diamond particles are bonded directly to each other, exposing at least one metal carbide cylinder having at least one hole extending through its thickness to both ends and being filled with a mass of diamond particles, for the following high pressure / high temperature sintering conditions: a pressure of at least 50,000 MPa at a temperature of at least 1300 ° C and within the diamond stable range; and reaction time 10-90 minutes, in a high pressure reaction cell, in which the metal carbide cylinder and diamond particles are arranged in a screen metal cup with a screen metal plate covering the open end of the cup, characterized in that at one end of the metal carbide cylinder containing the mass of the diamond particle is applied a disk of diamond catalyst / solvent and maintains the specified high pressure / high temperature sintering conditions until axial diffusion of the catalyst / solvent into the mass of diamond particles is obtained. 2. A process according to claim 1, characterized in that up to 2.5% by weight of catalyst solvent is mixed with the diamond particles. 3. A process according to claim 1 or 2, characterized in that a sheet of any of the heat-resistant metals zirconium, molybdenum, tantalum, tungsten and titanium is applied to the side of the catalyst / solvent sheet facing away from the metal carbide cylinder with the mass of diamond. 4. A method according to claim 1 or 2, characterized in that at least two sheets of one or more of the transition metals zirconium, molybdenum, tantalum, tungsten and titanium are applied to the end of the metal carbide cylinder with the mass of diamond facing away from the catalyst / 451 951 12 solvent disc. Process according to any one of the preceding claims, characterized in that (a) the metal carbide is selected from the group consisting of tungsten, titanium and tantalum carbides, (b) the catalyst / solvent is selected from the group consisting of cobalt, iron, nickel , ruthenium, rhodium, palladium, platinum, chromium, manganese, tantalum and mixtures of these elements, (C) the heat-resistant metal is selected from the group consisting of molybdenum, tantalum, tungsten and titanium and (d) the transition metal is selected from the group consisting of consists of zirconium, titanium, tantalum, tungsten and molybdenum. 6. A method according to any one of the preceding claims, characterized in that the metal carbide cylinder already contains a metal binder selected from the group consisting of cobalt, nickel, iron, chromium and mixtures of these metals. 7. A method according to any one of the preceding claims, characterized in that the size of the diamond particles varies from 0.1 to 75.4 m in largest dimension and that the metal carbide consists of cobalt-bonded tungsten carbide. 8. A method according to claim 1, characterized in that the metal carbide cylinder consists of a cylinder of cobalt-bonded tungsten carbide and that the mass of diamond particles has a size ranging from about 0.1 to 150 microns in largest dimension and that a plurality is applied. discs in each screen metal beaker in the following order: molybdenum disc, cobalt disc, tungsten carbide cylinder with diamond particles, cobalt disc, molybdenum disc, or: molybdenum disc, cobalt disc, tungsten carbide cylinder with diamond particles and 2 particle zinc particles. 9. A method according to claim 1, characterized in that in each screen metal beaker two cobalt disks are arranged, one on each side of the metal carbide cylinder with the diamond particles, and a molybdenum disk is arranged at each end of the shield metal so that the diffusion cup cobalt into the diamond material is provided. 10. A method according to any one of the preceding claims, characterized in that a metal carbide cylinder with diamond particles is arranged in each shield metal cup.