CH659786A5 - Process for making pressed-diamond wire-drawing dies and product from this process - Google Patents

Abstract

A process for making pressed-diamond wire-drawing dies of the type is described, which can generally be described as an inner polycrystalline diamond mass which is surrounded by a mass of metal-bonded carbide such as, for example, cobalt/sintered tungsten carbide and bonded thereto. It is known to make these drawing dies by high-pressure/high-temperature processes, typical conditions being 50 kbar and temperatures above 1300 DEG C. The improvement according to the invention comprises providing a group of discs of specific materials in specific arrangements within the reaction subassembly (for example metal carbide and diamond inside a zirconium cup). For example, a disc of a diamond catalyst/solvent and a disc of a refractory metal such as molybdenum are arranged on one side of the mass of metal carbide and diamond, and at least two discs of one or more transition metals such as zirconium are arranged on the other side. These discs are in general introduced into the interior of the subassembly cup. By means of this process modification, the process yields have been considerably improved by reducing the occurrence of defects in the drawing dies and by shortening the reaction time.

Description

** WARNING ** beginning of DESC field could overlap end of CLMS **.

PATENT CLAIMS 1. Process for producing wire drawing die Diamond compacts with a diamond-diamond bond, wherein at least one mass, which consists of a metal carbide cylinder, which has at least one hole that extends through its thickness from one end to the other, and contains the diamond particles in the holes, ei is subjected to a high pressure / high temperature process which is carried out in a high pressure reaction cell containing any mass of metal carbide and diamond particles within a subassembly which has a Has a shielding metal cup and a shielding metal disc, which covers the open end of the cup, characterized in that a subassembly is used, in which a layer has been inserted at one end of the mass of metal carbide and diamond, which consists of at least one catalyst / solvent for diamond exists, whereby an axial diffusion of the catalyst / solvent is achieved in the diamond, and that at high pressure / High temperature processes the following sintering conditions are used: pressure of at least 50 Kbar at a temperature of at least 1300C and within the range in which diamond is stable, and reaction time of 10 to 90 minutes.

2. The method according to claim 1, characterized in that (a) the metal carbide from the group formed by tungsten, titanium and tantalum carbide and (b) the catalyst! Solvents are selected from the group consisting of cobalt, iron, nickel, ruthenium, rhodium, palladium, platinum, chromium, manganese and mixtures thereof.

3. The method according to claim 2, characterized in that the metal carbide already contains a metal binding material which is selected from the group formed by cobalt, nickel, iron, chromium and mixtures thereof.

4. The method according to claim 3, characterized in that the size of the diamond particles in their largest dimension ranges from 0.1 to 75, and that the metal carbide is cobalt / tungsten carbide cemented carbide.

5. The method according to claim 1, characterized in that the layer is a composite layer consisting of a combination of a catalyst / solvent for diamond and a difficult-to-melt metal.

6. The method according to claim 5, characterized in that the metal carbide already contains a metal binding material which is selected from the group formed by cobalt, nickel, iron, chromium and mixtures thereof.

7. The method according to claim 6, characterized in that the composite layer comprises a layer of catalyst / solvent which is adjacent to the mass of metal carbide and diamond particles, and a layer of the non-fusible metal which comprises the layer of catalyst / solvent their side opposite to said mass is adjacent.

8. The method according to claim 6, characterized in that (a) the metal carbide from the group formed by tungsten, titanium and tantalum carbide, (b) the catalyst / solvent from that of cobalt, iron, nickel, ruthenium, rhodium, palladium , Platinum, chromium, manganese and mixtures thereof and (c) the refractory metal is selected from the group consisting of molybdenum, tantalum, tungsten, zirconium and titanium.

9. The method according to claim 6, characterized in that a layer of the difficult-to-melt metal is arranged adjacent to the mass of metal carbide and diamond particles on its side opposite the composite layer.

10. The method of claim 7, characterized in that each subassembly comprises in the following order: a layer of the refractory metal, the catalyst solvent for diamond, the mass of metal carbide and diamond particles, a second layer of the catalyst / solvent for diamond and a second layer of the hard-to-melt metal.

11. The method according to claim 9, characterized in that the catalyst solvent for diamond cobalt, the refractory metal of the composite layer is molybdenum and the refractory metal on the opposite side of the composition of the composition is zirconium.

12. The method according to claim 7, characterized in that the layer of catalyst / solvent is a disc made of this material and the layer of the metal which is difficult to melt is a disc made of this latter material.

13. Wire drawing stone diamond compact as a product of the method according to claim 1.

The invention relates to a method for the production of wire die diamond compacts according to the preamble of claim 1, and the product of this method.

A diamond compact or compact is a polycrystalline mass of diamond particles which are connected to one another and form an integral, tough, coherent, high-strength mass which has a diamond concentration of at least 70% by volume. Examples of diamond compacts are found in U.S. Patents 3,136,615; 3,141,746; 3,239,321; 3,609,818; 3,744,982; 3,816,085; 3,913280 and 3,944,398. A composite compact is a compact bonded to a substrate material such as cemented tungsten carbide or cemented carbide (see U.S. Patents 3,745,623 and 4,063,909). Press bodies can be used as blanks for cutting tools, straightening tools and wear parts.

U.S. Patent Nos. 3,831,428,4 129,052 and 4,144,739 describe wire drawing dies made from diamond compacts. A wire die diamond compact contains an inner mass of polycrystalline diamond (as described above under the term compact), which is surrounded by a mass of metal-bonded carbide, such as cobalt tungsten carbide, and is connected to this.

The actual wire drawing die is manufactured in various ways, generally by fitting or securing the wire drawing die compact in a high strength metal ring and making the wire drawing die as a through hole in the center of the polycrystalline diamond section using known means such as a laser. The draw could then be finished by pulling a wire impregnated with diamond dust back and forth through the draw. The drawing die can be preformed during the high pressure / high temperature sintering process if U.S. Patent 3,831,428, Col. 4, Numbers 54-60, and Fig. 4 are followed (a wire is previously placed in the polycrystalline core and can later removed by dissolving in a suitable acid).

The ZA patent application 77/5521 describes a wire die diamond compact, which is provided with a tantalum lining, which connects the carbide ring with the center

len polycrystalline diamond core connects. This patent application claims that the tantalum layer effectively connects the diamond core to the carbide surrounding it.

Both the wire die compacts according to US Pat. No. 3,831,428 and those according to the ZA patent application are produced by high-pressure / high-temperature sintering processes in which a catalytic metal, such as cobalt, penetrates radially from the surrounding metal carbide ring or cylinder (so-called Pull-through or sweep-through method). This catalyst accelerates the sintering process, which leads to the excessive diamond-diamond connection. The diamond compact quality depends on the degree of diamond-diamond connection in the microstructure. This connection appears to be achievable if a uniform and sufficient amount of cobalt is introduced into the grain boundaries during the high pressure / high temperature (HD / HT) conditions, during which other factors are constant.

The main problem in making large (e.g.

24 mm diameter) Pressed body die blanks is the inadequacy of cobalt diffusion due to a conventional radial pulling technique. It has been shown that the radial diffusion is not sufficient to create the desired cobalt concentration in the entire diamond core.

The investigations which led to the invention described here served to improve the catalyst diffusion in the larger drawing die blanks and to reduce the percentage of defective blanks which result from the known processes. Defects occur primarily in the form of both poorly bonded areas in the diamond core and cracking in the diamond or metal carbide section. Cracking occurs irregularly during various manufacturing processes, for example when pressing, grinding the outer circumference, surface grinding, lapping, and even under static conditions, which makes it very difficult to identify the cause. Defects are also identified by means of an X-ray examination. Another goal was to apply every successful technique to drawing die blanks of smaller size.

According to the invention, a method of the type mentioned at the outset is characterized by the combination of the method steps specified in claim 1 to achieve the stated object. Advantageous further developments of the method result from the dependent claims. With this method, the production of the larger wire die diamond compact (24.1 mm outer diameter and 12.0 mm inner diameter) can be carried out in more favorable yields than with the known technology. The process creates a uniform concentration and sufficient penetration of cobalt.

The known process steps and parameters for the production of wire drawing diamond compacts include a mass which consists of a metal carbide cylinder which has at least one through hole which extends through its thickness between the two ends and which contains diamond particles in the holes, following high pressure / Suspend high temperature sintering conditions: Pressure of at least 50 kbar at a temperature of at least 1300C and within the range in which the diamond is stable; Reaction time 10 - 90 min; all of which is carried out in a high pressure reaction cell containing the diamond particles and the metal carbide within a subassembly consisting of a protective or shielding metal cup and a protective or shielding metal disc covering the open end of the cup.

The tin metal can be zirconium among the metals. Titanium, tantalum, tungsten and molybdenum can be selected.

The area where diamond is stable. is the range of pressure / temperature conditions. among which diamond is thermodynamically stable. In a pressure-temperature-state diagram it is generally the high pressure side above the equilibrium line between diamond and graphite.

The improvement of this method according to the invention involves arranging on one side of the mass of metal carbide and diamond a disk which consists of a diamond catalyst / solvent and a disk made of a metal which is difficult to melt. each disk having a thickness of 25-102 µm. Usually at least two disks of one or more transition metals (e.g. zirconium, titanium, tantalum, tungsten or molybdenum) are placed at the end of the mass of metal carbide and diamond which is opposite to the side. on which the catalyst / solvent disk is arranged. These additional disks are usually located within the subassembly, which is delimited by the shield metal cup and the shield metal disc.

A preferred form of HDiHT device (although there are others) in which the improved method according to the invention can be carried out is the subject of US Pat. No. 2,941,248 (to which reference is made in more detail), which is known as a belt (belt)>) device describes. This contains two opposing sintered tungsten carbide stamps and in between a belt or molded part made of the same material. The molded part has a hole in which a reaction vessel is arranged.

which is shaped so that it can accommodate a filling assembly or reaction cell. A seal assembly is arranged between each stamp and the molded part, which consists of two heat-insulating and electrically non-conductive pyrophyllite parts and a metallic seal arranged between them.

In a preferred form, the reaction cell contains a hollow salt cylinder. The cylinder may be made of another material, such as Talcum, that (1) is not converted to a stronger, more rigid state during HD / HT operation (e.g., through phase transformation and / or compression). and (2) is substantially free of volume discontinuities that occur when exposed to high temperatures and pressures, such as occur with pyrophyllite and porous alumina. Materials which meet further criteria, which are described in US Pat. No. 3,030,662 (column 1, line 59-column.

2, line 2, to which reference is made for further details) are useful for the manufacture of the cylinder.

An electrical resistance heating tube made of graphite is arranged concentrically inside and on the salt cylinder and protrudes over the salt cylinder at both ends. A cylindrical salt sleeve is arranged concentrically within the graphite heating tube. The ends of the socket are provided with salt plugs, which are arranged above and below. The ends of the graphite heating tube are provided with pyrophyllite plugs on the inside and phyrophyllite rings on the outside.

which fill the space between the ends of the salt cylinder and the end of the graphite heating tube.

Electrically conductive metal end plates are used at each end of the reaction cell. to make an electrical connection with the graphite heating tube. There is an end cap assembly on each metal end disk, each of which has a phyrophyllite plug or a phyrophyllite disk, which is surrounded by an electrically conductive ring.

Operating techniques for simultaneous exposure to both high pressures and high temperatures in this type of device are known to those skilled in the high pressure field. The filling assembly fits into the space that is limited by the salt bushing and the salt plugs. The assembly consists of a cylindrical sleeve made of shield metal. One or more subassemblies are located within the shield metal sleeve.

The diamond particle mass, which is arranged in the subassembly, can also contain graphite and up to 2.5% by weight of catalyst / solvent. The mass of the diamond grains is arranged in one or more cavities or holes in a disk which is made from cold-pressed, sinterable carbide powder (a mixture of carbide powder and a suitable metal binder therefor). If only one die is made per subassembly, there is only one such hole, which is usually concentric with the metal carbide disc that forms a ring around the diamond core. If necessary, the ring or disc can be made from pre-sintered metal-bonded carbide or from fully sintered metal-bonded carbide.

It is also possible to manufacture wire drawing diamond compacts using the axial diffusion technique alone. A metal carbide that is free of any catalytic metals (e.g. cobalt) would be used. In this case the radial pull through of the solvent / catalyst would not be available and it would be delivered in its entirety using the axial diffusion technique.

The filling assembly is inserted into the reaction vessel which is inserted into the HD / HT belt device. First the pressure and then the temperature is increased and kept at the desired values for a sufficient time for sintering to occur. The sample is then allowed to stand for a short period of time (e.g.

3 min) to cool under pressure, and finally the pressure is reduced to atmospheric pressure (which may take about a minute) and the compact is removed.

The shield metal sleeve can be removed manually.

Any adhering metal from the shielding metal cup or shielding disc can be removed by grinding or lapping. Deformation or surface irregularity can be removed in the same way.

The metal carbide can be selected from tungsten, titanium or tantalum carbides; and the material that the metal compound creates in the cemented carbide (binder) can be selected from the group consisting of cobalt, nickel, iron, chromium and mixtures thereof. Cobalt cemented 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 being the most preferred material.

The refractory metals that are preferred for use in the disks in the method of the invention include molybdenum, tungsten, zirconium and titanium.

Of the transition metals, zirconium is preferred for use in the transition metal disks in the method of the invention.

A typical size range for the diamond particles, which are used as raw material in the manufacture of wire drawing diamond compacts, ranges from 0.1 µm to a largest dimension of 1 50 µm. The smaller sizes (01 - 45 µm) are preferred for wire drawing dies, which are used to pull wire if the wire is to have a fine surface.

Many experiments have been carried out to optimize the number of different disks and their arrangements, as shown by the samples given in Table 1 below. In this table and from here on, the term yield is defined as the number of finished blanks free of defects divided by the total number of blanks pressed.

1 shows a schematic view of a subassembly in longitudinal section, while FIGS. 2 to 6 show the configuration of such subassemblies. 1 to 6, the reference symbols and the corresponding drawing symbols mean the following: 1 = zirconium screen metal disc 2 = diamond particles 3 = cobalt tungsten carbide ring 4 = zirconium screen metal cup The shielding metal cup is preferably flanged over the shielding metal disc, as shown by the symbol above.

Table 1 Different subassembly configurations Configuration Yield Process reliability Fig. 2 40-60% inconsistent and unreliable Fig. 3 50-70% inconsistent Fig. 4 90-100% reliable and reproducible Fig. 5 90-100% reliable and reproducible standard procedure 50-70% ren according to US Pat. No. 3,831,428. The results in Table 1 come from HD / HT experiments in which wire drawing diamond pressed bodies with the following nominal dimensions have been produced: 13.7 mm outside diameter, 5.1 mm diamond core diameter and 3.8 mm thickness. All of the slices used were approximately 50 µm thick. The best success was achieved with configurations 3 and 4.

For the larger diameter drawing dies, it has proven desirable to use eight additional zirconium disks on the top (i.e. above the molybdenum disk) and a total of eight zirconium disks on the opposite side of the metal carbide and diamond mass.

Another variation according to FIG. 6 has also been used successfully. This configuration differs from the subassembly described in the above paragraphs in that two catalyst / solvents Disks have been used, one on each side of the metal carbide. In addition, the selected transition metal Molybdenum instead of zirconium, and it is used outside the Shielded metal cup arranged. In addition, Molyb dan has been used for the washer made of difficult-to-melt metal and has been arranged outside the shielding metal washer.

Configuration No. 4 with the addition of a zirconium disc on the underside of the shield metal cup has proven to be the optimal configuration.

When manufacturing wire drawing blanks from Tungsten carbide press cracking has been reduced from 520% (using the tantalum lining process) to 510% using the method of the invention and the total cracking in the blank has been reduced from 30% to 20%. In addition, the method according to the invention can be carried out in a shorter period of time (75 min under HD / HT conditions versus over 90 min, which are typical of the tantalum lining process), which results in greater production output. In addition, the lapping time has been reduced considerably. It has been shown that the Knoop hardness of the diamond core of these large die compacts produced by the method according to the invention is practically equivalent to the hardness of compacts produced by the tantalum lining method is.

Experiments on pressed bodies with an outer diameter of 13.7 mm have shown that the Knoop hardness is equivalent to a value. which is slightly lower than the value for compacts. which have been produced by the process according to US Pat. No. 3,831,428. but the difference was not big enough. to adversely affect the performance of the drawing die. In these experiments, the reject determined by the X-ray method was also reduced from 10 - 30% to 5 - 10'0.

and the cracking of the blanks. that came from the press. was reduced from 15-35% to 0-5%.

Promising results have also been achieved with the smaller compacts (e.g. 0.89 mm diamond core diameter). which go from 67% yield with the method according to US Pat. No. 3,831,428 to 9500 yield with the axial cobalt diffusion.

Claims (13)

PATENT CLAIMS 1. Process for producing wire drawing die Diamond compacts with a diamond-diamond bond, wherein at least one mass, which consists of a metal carbide cylinder, which has at least one hole that extends through its thickness from one end to the other, and contains the diamond particles in the holes, ei is subjected to a high pressure / high temperature process which is carried out in a high pressure reaction cell containing any mass of metal carbide and diamond particles within a subassembly which has a Has a shielding metal cup and a shielding metal disc, which covers the open end of the cup, characterized in that a subassembly is used, in which a layer has been inserted at one end of the mass of metal carbide and diamond, which consists of at least one catalyst / solvent for diamond exists, whereby an axial diffusion of the catalyst / solvent is achieved in the diamond, and that at high pressure / High temperature processes the following sintering conditions are used: pressure of at least 50 Kbar at a temperature of at least 1300C and within the range in which diamond is stable, and reaction time of 10 to 90 minutes. 2. The method according to claim 1, characterized in that (a) the metal carbide from the group formed by tungsten, titanium and tantalum carbide and (b) the catalyst! Solvents are selected from the group consisting of cobalt, iron, nickel, ruthenium, rhodium, palladium, platinum, chromium, manganese and mixtures thereof. 3. The method according to claim 2, characterized in that the metal carbide already contains a metal binding material which is selected from the group formed by cobalt, nickel, iron, chromium and mixtures thereof. 4. The method according to claim 3, characterized in that the size of the diamond particles in their largest dimension ranges from 0.1 to 75, and that the metal carbide is cobalt / tungsten carbide cemented carbide. 5. The method according to claim 1, characterized in that the layer is a composite layer consisting of a combination of a catalyst / solvent for diamond and a difficult-to-melt metal. 6. The method according to claim 5, characterized in that the metal carbide already contains a metal binding material which is selected from the group formed by cobalt, nickel, iron, chromium and mixtures thereof. 7. The method according to claim 6, characterized in that the composite layer comprises a layer of catalyst / solvent which is adjacent to the mass of metal carbide and diamond particles, and a layer of the non-fusible metal which comprises the layer of catalyst / solvent their side opposite to said mass is adjacent. 8. The method according to claim 6, characterized in that (a) the metal carbide from the group formed by tungsten, titanium and tantalum carbide, (b) the catalyst / solvent from that of cobalt, iron, nickel, ruthenium, rhodium, palladium , Platinum, chromium, manganese and mixtures thereof and (c) the refractory metal is selected from the group consisting of molybdenum, tantalum, tungsten, zirconium and titanium. 9. The method according to claim 6, characterized in that a layer of the difficult-to-melt metal is arranged adjacent to the mass of metal carbide and diamond particles on its side opposite the composite layer. 10. The method of claim 7, characterized in that each subassembly comprises in the following order: a layer of the refractory metal, the catalyst solvent for diamond, the mass of metal carbide and diamond particles, a second layer of the catalyst / solvent for diamond and a second layer of the hard-to-melt metal. 11. The method according to claim 9, characterized in that the catalyst solvent for diamond cobalt, the refractory metal of the composite layer is molybdenum and the refractory metal on the opposite side of the composition of the composition is zirconium. 12. The method according to claim 7, characterized in that the layer of catalyst / solvent is a disc made of this material and the layer of the metal which is difficult to melt is a disc made of this latter material. 13. Wire drawing stone diamond compact as a product of the method according to claim 1. The invention relates to a method for the production of wire die diamond compacts according to the preamble of claim 1, and the product of this method. A diamond compact or compact is a polycrystalline mass of diamond particles which are connected to one another and form an integral, tough, coherent, high-strength mass which has a diamond concentration of at least 70% by volume. Examples of diamond compacts are found in U.S. Patents 3,136,615; 3,141,746; 3,239,321; 3,609,818; 3,744,982; 3,816,085; 3,913280 and 3,944,398. A composite compact is a compact bonded to a substrate material such as cemented tungsten carbide or cemented carbide (see U.S. Patents 3,745,623 and 4,063,909). Press bodies can be used as blanks for cutting tools, straightening tools and wear parts. U.S. Patent Nos. 3,831,428,4 129,052 and 4,144,739 describe wire drawing dies made from diamond compacts. A wire die diamond compact contains an inner mass of polycrystalline diamond (as described above under the term compact), which is surrounded by a mass of metal-bonded carbide, such as cobalt tungsten carbide, and is connected to this. The actual wire drawing die is manufactured in various ways, generally by fitting or securing the wire drawing die compact in a high strength metal ring and making the wire drawing die as a through hole in the center of the polycrystalline diamond section using known means such as a laser. The draw could then be finished by pulling a wire impregnated with diamond dust back and forth through the draw. The drawing die can be preformed during the high pressure / high temperature sintering process if U.S. Patent 3,831,428, Col. 4, Numbers 54-60, and Fig. 4 are followed (a wire is previously placed in the polycrystalline core and can later removed by dissolving in a suitable acid). The ZA patent application 77/5521 describes a wire die diamond compact, which is provided with a tantalum lining, which connects the carbide ring with the center ** WARNING ** End of CLMS field could overlap beginning of DESC **.