DE2413166A1 - WIRE DRAWING DIE - Google Patents

Description

"Wire drawing die"

A polycrystalline diamond wire drawing die is described in U.S. Patent No. 3,407,445. US Pat. No. 3,743,483 describes composite bodies made of polycrystalline diamond and cemented carbide which are suitable for insertion in tools, the polycrystalline diamond being bonded directly to the cemented carbide. From DT-OS 2,232,227 and existing polycrystalline cubic boron nitride and cemented carbide composite body for removing material embedding bear known in which the polycrystalline cubic boron nitride is directly connected to the cemented carbide.

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Wire drawing dies with a single diamond crystal are preferred for drawing fine tungsten wires. Such wire drawing dies are, however no longer economical for larger wire diameters (over 0.2 mm), since the required single diamond crystal is too large and therefore it is too expensive and also breaks easily. Used for drawing tungsten wire 0.25mm in diameter and above Therefore, wire drawing dies made of cemented carbide are generally used, but they have a relatively short service life.

Diamond wire drawing dies are commonly made from a natural single crystal diamond set in a sintered metal matrix is supported. The diamond is placed in a mounting ring and the space between the diamond and the The socket ring is filled with a metal that can be sintered together, which is then sintered. Only sintered metals are allowed can be used, through which the diamond is not attacked during sintering. Metals with high strength and high modulus of elasticity are therefore not suitable, since such metals are strong carbide formers and are therefore not suitable for those required for sintering high temperatures would attack the diamond.

Have the sinterable metals suitable for setting diamond so a low modulus of elasticity and a low yield strength and therefore do not allow the exercise of a

2 noticeable bias pressure (greater than about 7 kg / mm) on the surface of the diamond single crystal. Well-known diamond matrices set in sintered metal can be used at room temperature

2
can be pretensioned at about 7 kg / mm, but this pretension decreases very rapidly with increasing working temperature when the wire drawing process is carried out at elevated temperatures.

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Diamond has a low tensile strength and it would therefore be of particular advantage to compensate for this disadvantage if one were to

2 the diamond surface constantly exerts a pressure of over 7 kg / mm could exercise.

The same mounting problems occur with the polycrystalline diamond wire drawing dies described in US Pat. No. 2,407,445 on. Instead of using a sintered metal matrix, however, one could also try using the diamond drawing nozzle of a pressing pressure to fit into a mounting ring, but then the irregular outer surface of the diamond drawing nozzle would have to be ground to a press fit, which is forbidden for economic reasons.

The invention is based on the object of an improved wire drawing die to create, with the particular wires made of high-strength and hard metals such as tungsten, molybdenum, steel, etc. at elevated temperatures can be drawn. The invention now provides such an improved wire drawing die. The compound Wire drawing die according to the invention has, in its simplest form, an outer jacket made of cemented carbide which encloses a crystalline core made of diamond, cubic boron nitride or polycrystalline mixtures of these hard materials, through which a centrally located hole extends, in which the drawing material is deformed and adjusted to the appropriate dimensions is brought. In a preferred embodiment of the invention (for drawing wires with a diameter of 0.2 mm and above) is at least one high-strength metal ring with a press fit around a composite body with a jacket made of sintered hard

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metal and a core made of polycrystalline diamond. at this arrangement is applied to the outer surface of the composite body

continuously exerted a noticeable compressive stress (over 7 kg / mm).

The invention will now be explained in more detail with reference to drawings, in which show:

1 shows a section through a wire drawing die in the form of a composite body with a polycrystalline core and essentially cylindrical shape, through which a double-conical hole extends and which is surrounded by a jacket made of cemented carbide which is directly connected to the core,

Fig. 2 shows a section through a having the shape of a rotating body Composite die with a polycrystalline core layer, each with on the top and bottom a cemented carbide layer (as well as an outer layer made of one piece with these layers) is directly connected, the polycrystalline mass at least the constriction area of a double-conical Wire drawing nozzle opening encloses,

3 shows a partial section of a device for producing which is suitable for producing the composite bodies according to the invention of high pressures and temperatures,

4 shows a section through a charging arrangement for the pressure chamber of the device according to FIGS. 3 and

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5 and 6 embodiments of wire drawing dies provided with pressure rings according to the invention.

It has long been known that diamond matrices, especially those for pulling thicker wires (i.e. wires 0.3 mm in diameter and larger) tend to crack before they . have reached a level of wear that requires replacement. This failure is due to insufficient support of the diamond, which has a low tensile strength. Since to produce a support for the diamond so far only a limited one As a selection of metals was available, there was no sufficient compressive stress on the outer surface of a single diamond crystal exercise, especially at high working temperatures.

An essential feature of the invention is therefore the creation of an ideal support material for the die core, which actually contributes to increasing the strength of the die core, is extremely stiff and, moreover, also easy to use Rotary body can be shaped so that it can be arranged within strong clamping rings. The binding material must be high Can absorb compressive forces from the clamping rings and transfer them to the die core so that these compressive forces are used during the drawing process be able to counteract and compensate for any tensile forces that occur. The support material must be between the polycrystalline or monocrystalline die core and the clamping ring assembly are arranged that a considerable compressive stress is permanent on the Surface of the die core is exercised.

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It has been found that the ideal support material is cemented carbide which is best placed between the die core and the clamping ring or rings by using it. is connected directly to the die core. In a preferred embodiment, the cemented carbide has the shape of a jacket, the outer surface of which is adapted to the inner surface of the clamping ring, the composite body consisting of the die core and cemented carbide encloses. When the die core is directly connected to the cemented carbide, the use of high temperatures results and pressures an excellent bonding area between the core material and the cladding material, which the compensates for different coefficients of thermal expansion of the two materials. This point of view is both in the manufacture the composite matrix as well as when using the composite matrix in the heated state.

1 shows a preferred embodiment of a composite body 10, the core 11 of which has an essentially cylindrical shape and has a correspondingly sized and shaped through hole 12. The core 11 consists of a polycrystalline A mass of diamond crystals and / or cubic boron nitride crystals, but could also be a single diamond crystal. The jacket 13 is made made of cemented carbide, which is directly connected to the die core 11 along an interface which is free of voids as well runs irregularly and toothed in a region having a thickness of approximately 1-1OCKu, the toothing between individual crystals and parts of the cemented carbide mass occurs. This interface formation is both polycrystalline and also single crystal diamond. A diamond single crystal becomes

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microscopically etched, the etched out areas with cemented carbide are filled.

In the embodiment shown in FIG. 2, the composite body consists 20 made of a crystalline inner layer 21, which is initially coated with an outer layer 22a and 22a on the underside. 22b covered and laterally encased by a ring layer 22c. The cemented carbide layers 22a, 22b and 22c consist of one piece in the finished state of the composite body. In both embodiments, the composite bodies are in the form a rotating body (preferably a conical rotating body with a cone angle of 2-4). The constriction area, i.e. the area with the smallest diameter of the hole 23 consists of a material with high wear resistance.

To produce the composite bodies 10 and 20 are preferably used the device explained in US Pat. No. 2,941,248 and partially shown in FIG. 3 for generating high pressures and high temperatures. Fig. 4 shows a loading arrangement suitable for the manufacturing method according to the invention.

The device 30 shown in Fig. 3 includes two punches 31 and 31 'made of tungsten carbide hard metal and one between them arranged belt ring 32 made of the same material. A reaction vessel 34 is arranged in the opening 33 of the belt ring 32, which accommodates the loading arrangement described below. Between the belt ring 32 and the punch 31 and the punch 31 * an insulating sealing arrangement 35 is provided in each case

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see the two thermally insulating and electrically non-conductive Components 36 and 37 made of pyrophyllite, between which a metallic seal 38 is arranged.

In a preferred embodiment, the reaction vessel 34 contains a hollow cylinder 39 made of salt. The hollow cylinder 39 can also be made of another material, for example talc which a) under the high pressures and high temperatures used does not turn into a firmer and more rigid one State is transferred (by phase change and / or compression) and which b) free from when high pressures are applied and volume discontinuities occurring at high temperatures; as is the case with pyrophyllite and porous aluminum oxide appear. For the production of the hollow cylinder 39, materials are suitable which correspond to those in column 1, line 59 - column 2, line 1 of the US Pat 3 030 662 meet the conditions listed.

Concentrically within the cylinder 39 is a bearing against the cylinder 39 Resistance heating tube 40 made of graphite is arranged. Inside the heating tube 40 there is again a cylindrical salt sleeve 41 arranged, on the top and bottom of each a salt plug 42 and 42 * is fitted.

At each end of the cylinder 39, an end plate 43 or 43 ′ made of electrically conductive metal is provided, which creates an electrical connection to the heating tube 40. ^{An end cap 44 or 44 J} , which consists of a pyrophyllite disk 45 which is enclosed by an electrically conductive ring 46, is arranged over each end disk 43 or 43 *.

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In the device explained above, in known Generate high temperatures and high pressures at the same time. Of course, others can also be used to generate the required high pressures and temperatures suitable devices are used.

The charging arrangement 50 shown on a different scale in FIG. 4 fits into the pressure chamber 41 of the device Fig. 3. The feed assembly 50 consists of a cylindrical sleeve 52 made of a shielding metal made of zirconium, Titanium, tantalum, tungsten or molybdenum can be made. Inside the cylindrical sleeve 52 is a shielding metal through a disk 54 closed cup 56 made of shielding metal is provided. The bowl filling shown in Fig. 4 is used for production a composite body with a polycrystalline core having a straight hole through it. A wire 57 corresponding Large wire, for example a tungsten wire with a diameter of 0.25 mm, is arranged inside the cup 56 and on the cup bottom attached, for example welded on. The wire 57 is made of a mass 58 of hard material particles (diamond, cubic boron nitride or a mixture of diamond and cubic boron nitride) enclosed, which fills the interior of a socket 59, the consists of cold-pressed sinterable hard metal powder mixture (made of carbide and a suitable binding metal). The socket 59 can optionally also consist of pre-sintered hard metal, as will be explained below.

To make the one that extends through the polycrystalline core Hole, tungsten is particularly well suited because it has a high melting point and is also sufficiently rigid.

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sits to prevent deformation caused by the crystal grains in the to withstand high temperatures and pressures occurring pressing and sintering process. Tungsten can also not be too difficult later on be dissolved or abraded. Other materials can also be used, for example molybdenum, zirconium, Titanium, tantalum, rubidium, rhodium, rhenium, osmium or refractory carbides and even non-metals such as oxide ceramics. Of the Wire does not need to have a uniform cross-section, but rather may have a shape which facilitates the desired double-conical formation of the preformed hole.

The remaining remaining volume within the loading arrangement 50 is made of disks 61a, 61b made of the same material as the Cylinder 39, for example sodium chloride, and filled with disks 62a, 62b made of hexagonal boron nitride. The discs 62a, 62b are intended to prevent undesired substances from entering the sample receiving space defined by the well 56 and the disk 54. It has been found that using either zirconium or titanium for sleeve 52, disc 54 and the cup 56 these metals the sintering of the crystal grains and the Promote connection between the crystalline mass and the cemented carbide jacket.

example 1

A bushing 59 with an inner diameter of 2.56 mm was made from cold-pressed hard metal powder mixture (13% by weight cobalt, 87 wt.% Tungsten carbide) and arranged in a zirconium bowl, on the bottom wall of which a tungsten wire with a

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Diameter of 0.25 mm was welded, which in the manner shown in Fig. 4 in the middle of the cup along it Long axis extended. The cavity between the socket and the tungsten wire was filled with diamond grit with a sieve size filled in by 40/80 stitches / cm. Zirconium metal (with a Thickness of 0.050 mm). This charging arrangement was in the device shown in Fig. 3 for producing high pressures and high temperatures introduced and there for 60 minutes approximately a pressure of 55 kilobars and a temperature exposed to 1500 C, whereupon the temperature returns to room temperature and then the pressure was turned off. The diamond-cemented carbide composite body removed from the device was approximately 5.84 mm in diameter and approximately 5.59 mm in length. In a hot bath of HF and ENT the tungsten wire, the outer zirconium sleeve and some cemented carbide were removed from the surface. Then was a protective coating of molten polyethylene is applied to the surface of the composite, followed by the etching process continued to completely remove the tungsten wire.

When using a mass 58 of diamond crystals, a very extensive diamond-diamond bond is obtained, as in FIG U.S. Patent No. 3,743,483. When using cubic boron nitride crystals or a mixture of cubic boron nitride crystals and diamond crystals, a metallic one must also be used Add phase, the aluminum atoms and atoms of at least one alloy element from the nickel, cobalt, manganese, iron, Contains group comprising vanadium and chromium. The relationship

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the amount of aluminum in relation to the amount of alloy metal is not critical and can be from equal parts by weight to one Part aluminum per 10 parts alloy metal is sufficient. The amount of aluminum in the starting material can be 1 to about 40 wt.% of the cubic boron nitride, while the alloy metal amount from 2 to about 100% by weight of the cubic boron nitride can be enough. The amount of these alloy metals remaining in the compacted cubic boron nitride as matrix material depends on the amount of pressure applied and the duration of the pressure and temperature application. In each case amounts to the amount of aluminum plus alloy metal in the compacted cubic boron nitride is more than 1% by weight of the cubic boron nitride.

The preferred size range for the diamond grains / is 90-105 mesh / cm (corresponding to a US sieve size of 230-270 mesh) and for cubic boron nitride is 0.1-10 yU. Of course, other sizes can also be used. The size of the diamond grains can range from approximately 0.1 μm to approximately 500 μm in the largest dimension and the cubic boron nitride grains can have a size from 0.1 to 20 μm in the largest dimensions.

When using diamond grains, the initial content of the die core is 100 percent by volume diamond, which is a finished product Die core results, which consists of 90-98 volume percent diamond and 2-10 volume percent binder metal of the cemented carbide. In any case, the diamond concentration in the finished die core must be greater than 70 percent by volume for a diamond-diamond bond is guaranteed. With an initial diamond concentration of 70-90 percent by volume, interchangeable carbide powder can be used

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or metal powder can be mixed with the diamond.

When using cubic boron nitride grains, the preferred is Initial composition of the die core 80-97 volume percent cubic boron nitride, the remainder metallic substance. The finished one The die core contains the cubic boron nitride, the metallic medium present in different phases and some binding metal the cemented carbide.

When producing a composite matrix with a diamond core For example, the feed assembly 50 is placed in the apparatus 30, pressurized therein, and then heated. Temperatures in The range of 1300-1600 C will be used for about 3 minutes Sintering of the carbide-binder metal mixture is maintained and at the same time a very high pressure, for example of the order of magnitude, is maintained of 55 kilobars, exercised to ensure thermodynamically stable conditions for the diamond. At 1300 C should the minimum pressure should be approximately 50 kilobars and at 1400 C the minimum pressure should be approximately 52.5 kilobars. For the application Reaching temperatures will of course melt the binder metal component of the system, leaving some binder metal is available for displacement from the mass 59 into the mass 58, where it acts as a solvent catalyst for diamond formation must act, especially when making a polycrystalline Diamond core.

When making a composite die with one made of cubic boron nitride or of cubic boron nitride and diamond At its core, the charging arrangement 50 is fed into the device 30

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brought, pressurized and then heated. There are temperatures applied in the range of approximately 1300-1600 C for more than 3 minutes while at the same time the system was very high Is exposed to pressures, for example in the order of 55 kilobars, in order to achieve thermodynamically stable conditions for the ensure cubic boron nitride in the system. At 1300 C the minimum pressure should be around 40 kilobars and at 1600 C the minimum pressure should be be approximately 50 kilobars. At the temperatures used, the binding metal contained in the mass 59 is melted, so that, depending on the composition of the cemented carbide powder, cobalt, nickel or iron for displacement from the Mass 59 in mass 58 is available where it is with the molten aluminum alloy that is present or formed in the mass 58. The metallic phase thus formed acts as an effective binder for the cubic boron nitride crystals near the interface between mass 58 and mass 58 and binds these crystals to each other and to the cemented carbide. the remaining crystals in the cubic boron nitride mass are due to the existing alloy (introduced or formed in place) and bound together by reaction of this alloy with cubic boron nitride.

The one created between the high-strength and wear-resistant core and the surrounding or flanking rigid cemented carbide direct bonding makes the interposition of any connecting layer between the core and the outer jacket superfluous. The rigid, rigid support material in direct contact with the die core (i.e. with the mass 11 or with the mass 21) results in a composite body which, due to the complementary nature of the materials used in combination, is unusually

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Hch solid and durable. The bond at the interface is qualitative so good that the interface is generally stronger than the tensile strength of the crystal grains.

If a hard metal sintering powder is used, preference is given to a tungsten carbide sintering powder (mixture of tungsten carbide powder and cobalt powder), which is commercially available in particle sizes of 1-5 u. If desired, tungsten carbide can be replaced in whole or in part by titanium carbide and / or tantalum carbide. Small amounts of other carbide powders can also be added to achieve certain properties of the composite body. Some nickel and iron have also been used to bind the carbide particles. Cobalt, nickel, iron and mixtures of these metals can therefore be used as the binding metal for the carbide particles. However, cobalt is preferred as the binder metal. The sintered powders suitable for practicing the present invention can contain about 75-94 % carbide and about 6-25% metal binder. For example, a powder of 6 % cobalt and 94 % tungsten carbide or of 13% cobalt and 87% tungsten carbide can be used. If necessary, presintered bushings (Fig. 1) or discs (Fig. 2) can be produced using the powder mixtures described above. These pre-sintered bodies can then be used instead of the cold-pressed bodies.

You can also make composite dies without a hole, with a straight hole or with a double-conical hole, but you have to In any case, machine the hole to the exact dimensions. Editing is made easier if there is already a continuous There is a hole through which a wire impregnated with diamond dust can be passed. If necessary, one can use the

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Provide the trizenkern with an exit hole with the help of a laser. If the holes in the die cores become larger as a result of normal wear and tear and erosion, the holes can be used to pull Rework wires with a larger diameter.

After having a composite body (for example a composite body 10 or 20) with a precisely dimensioned through hole, it is advantageous to give the composite body a precise Machining its outer surface to give it the shape of a solid of revolution (for example the shape of a cylinder or a truncated cone). The corresponding essentially concentric Composite bodies machined rotationally symmetrically to the through hole can then be placed within one or more clamping rings be arranged, creating a compressive stress of up to over

2
70 kg / mm can be exerted evenly on the composite body. With appropriate dimensioning and fitting, this compressive stress is continuously and evenly transferred to the core of the composite body via the outer jacket of the composite body. The clamping or fitting rings can be made from a suitable material that is still high-strength under the working conditions, for example from superalloys, stainless steel, high-strength, dispersion-hardened steel alloys, reinforced metals or plastics or cemented carbides.

In the embodiment according to FIG. 5, the outer jacket is sintered hard metal of the composite body 70 shaped to be exactly cylindrical. In order to achieve a press fit, the composite body 70 (e.g. has an outer diameter of 0.3020 inches), into a metal ring 71 (with an inner diameter of 0.3017 inches)

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pressed. The outer surface of the metal ring is conical, preferably with a conicity of 2-4%, and the conical inner surface of a metal ring 72 into which the arrangement consisting of the composite body 70 and the metal ring 71 is pressed will. A locking ring 73 can also be provided to hold the die arrangement together when it bursts.

In the case of a die arrangement for drawing tungsten wire, the ring 71 can, for example, be made of the steel alloy H-21, the ring 72 made of a superalloy (Ren £ 41) and the ring 73 made of stainless Made of steel. In the case of a die arrangement for drawing a softer material - at lower temperatures, for example For drawing copper wires, all rings can be made of stainless steel.

The die assembly shown in Fig. 6 is easier to assemble and consists of fewer parts. In the embodiment according to FIG. 6, the outer surface is the sintered hard metal outer jacket The composite matrix 80 is ground exactly to the shape of a truncated cone with a conicity of 2-4%. The conical one The composite body sits with a press fit within a ring 81. Similar to the embodiment according to FIG. 5, a safety ring 82 may be provided. The compressive forces are exerted by the ring 81.

It can also be made die arrangements in which a cylindrically shaped composite die with a shrink fit Support ring is adapted. These matrix arrangements are suitable for

ο pulling wires at low temperature (below about 100 C),

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for example for drawing copper wires. With such matrix arrangements the compressive stress that can be exerted on the composite die is limited to lower values.

Of course, the hole passing through the die core does not necessarily have to have a cylindrical cross section. Instead of a polycrystalline diamond mass, the diamond can also consist of a single diamond crystal, provided that only on the diamond core a sufficient clamping pressure is exerted and therefore the forces occurring during wire drawing are exerted by the binding rings which have a high tensile strength, while diamond has a low tensile strength.

Example 2

A thick-walled socket with a length of approximately 3.81 mm, a bore of approximately 2.5 mm and an outside diameter of 6.35 mm was made from a cold-pressed powder mass of 87% by weight tungsten carbide and 13% by weight cobalt. the Bushing was inserted into a precisely fitted zirconium cup with a wall thickness of approximately 0.05 mm, followed by the central bore Artificially produced diamond grain with a sieve size of 90/105 meshes / cm was introduced and lightly tamped down. Then two zirconium discs with a diameter of approximately 6.35 mm and a thickness of 0.05 mm each were created placed on top of the diamond-filled socket. The zirconium bowl with the diamond-filled socket was in given a zirconium tube with a wall thickness of 0.025 mm. This arrangement was placed in a sleeve made of pressed salt, which was arranged inside a graphite tube, as in

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Connection with Fig. 3 was explained. The assembly was pressurized to approximately 55 kilobars and then for 60 minutes heated to a temperature of 1550 C. After cooling and subsequent pressure reduction, the diamond became the socket containing well removed in the form of a solid cylinder. The adhering zirconium was dissolved in an HF-ENT mixture and an end face of the cylinder was polished on a diamond lapping wheel. On the polished face of the diamond core extensive diamond-diamond bonding was found. the The cylindrical outer surface of the sintered hard metal jacket was then Ground to a diameter of 5.18 mm. A ring with an inner diameter of 5.14 mm was made from soft steel, an outside diameter of 38.1 mm and a thickness of 12.7 mm

'produced and heated to a temperature of 400 C. The honed one The diamond core cylinder was then quickly pressed into the heated steel ring, whereupon the assembly was allowed to cool left. Finally, through the diamond core, a hole suitable for drawing tungsten wire with a diameter of 0.38 mm and the completed die assembly was then used to draw tungsten wire, with the die on a Temperature of about 400 ° C and the wire was preheated to about 800 ° C.

After about 54 kg of tungsten had been drawn through the die, one could see the size and shape of the drawn wire see that the diamond core of the die had cracked as a result of the forces exerted by the continuous wire. The ones from soft steel ring compressive forces exerted radially on the diamond core were obviously inadequate in terms of working conditions. However, the life of the die corresponded to the life

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a die fitted with a natural single crystal in the given working conditions.

Example 3

Using diamond grain and a tungsten carbide bushing and cobalt, a feed assembly similar to that of FIG. 2 was made, but with the bushing having a hole with a 3.18 mm in diameter. The one encapsulated in zirconium The feed assembly was subjected to high pressure and high temperature as in Example 2. The obtained cylindrical die body was ground to an outside diameter of 5.18 mm and as in example 2 pressed into a ring made of mild steel.

A hole for drawing tungsten wire with a diameter of 0.325 mm incorporated. The die was then placed under working conditions used, which were similar to the working conditions set out in Example 2.

After about 700 kg of tungsten wire had been pulled through the die, the cylinder got play within the steel ring and the die was then taken out of service and checked. It turned out that the die was neither cracked was still noticeably worn and that further use was no longer advisable because of the loose play within the steel ring. Nevertheless, the service life was twice as long as that of a conventional die with a single diamond crystal. the

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Die was then placed in a new ring, which exerted stronger compressive forces, and a larger one for pulling wire Drilled out diameter. After being used again, the overhauled die showed a satisfactory behavior.

Example 4

A composite body with a tungsten carbide-cobalt cemented carbide Sheathed polycrystalline diamond core was produced as in Example 3 and to an outside diameter of 5.18 mm sanded. The ground composite body was pressed into a hardened and ground ring made of hot-forged tungsten steel, which had an inner diameter of 5.17 mm and a conical outer surface with an outer diameter of 11.4 mm at one end and an outside diameter of 11.55 mm at the other End owned. The ring with the press-fit composite body was pushed into the conical opening with a force of approximately 1360 kg of a ring made of the superalloy Ren4 41. The ring had a thickness of 12.7 mm and an outside diameter (including a protective ring made of stainless steel with a thickness of 1.57 mm) by 38.1 mm. The ring exercised on the inside

2 a compressive stress of approximately 84 kg / mm which counteracts the bursting forces exerted during wire drawing. The completed die assembly was that shown in FIG Similar arrangement.

The diamond core was provided in a conventional manner with a drawing hole for drawing tungsten wires with a diameter of 0.33 mm Mistake. Within several. Months were

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Tr'izen arrangement of hot tungsten wire in an amount of ί 100 kg drawn. The die looked like new and was still used. With a conventional one used under the same working conditions The diamond die could only be drawn a fraction of the above amount of wire.

Example 5

A cylinder made from a sintered mixture of tungsten carbide and cobalt (87% by weight WC, 13% by weight 0o) with an outside diameter of 8.81 mm and a length of about 6.35 mm was provided with a hole 4.32 mm in diameter. The hole was filled with synthetic diamond powder with a sieve size of 90/105 mesh / cm. The rinit filled diamond The cylinder was wrapped in a zirconium foil with a thickness of 0.013 mm and placed in the pressure chamber of the device described given for generating high pressures and high temperatures. The loading arrangement was a pressure of approximately Exposed 55 kilobars while heating it to a temperature of approximately 1550 C for 58 minutes. After cooling down the pressure was switched off and a solid cylinder was removed from the pressure chamber. The zirconium outer layer was made with An abrasive was removed and each face of the cylinder was polished on a diamond lapping device until the ends of the diamond core were flat and could be observed under the microscope. The diamond core consisted of many grains that were firmly attached to one another were connected, showing extensive diamond-diamond bonding. The length of the cylinder was 5.21 mm. The peripheral surface of the cylinder was ground to a taper of 2%, see above

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that the thicker end has a diameter of 8.36 mm and the thinner one End had a diameter of 8.26 mm.

A ring was made from stainless steel (no 18-8), the one Thickness of 9.52 mm and an outside diameter of 25.4 mm and the inside opening of which had a conicity of 2%, whereby the diameter at the larger end was 7.30 mm. The diamond-carbide composite cylinder was pressed into the opening of this ring with a force of approximately 227 kg, making an arrangement arose, which had the shape shown in Fig. 6, but had no safety ring. The outer steel ring exercised through it exerted a compressive stress on the composite cylinder of approximately 28 kg / mm.

In the diamond core of this arrangement, a die for drawing copper wires with a diameter of 1 mm incorporated a corresponding drawing hole. With this matrix arrangement, over 2270 kg of copper wire were produced within a few months produced, which had an excellent surface quality for applying insulating varnish. The polycrystalline drawing surface seems to improve the lubrication of the wire passing through the draw hole by removing lubricant from the incoming wire Wire holding on. The die assembly was then advanced to wire drawing used.

Example 6

One with an outside diameter of 8.81 mm and a length of 3.18 mm A cylinder made of a cemented carbide consisting of 87% by weight of WC and 13% by weight of Co was provided with a central opening with a

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Diameter of 3 ", 18 mm. This hollow cylinder was placed in a zirconium cup with a wall thickness of 0.05 mm and the central opening was filled with a powder mixture composed of 94 percent by volume of cubic boron nitride with a particle size between 0.1 and 10 η and 6 percent by volume NiAl with a sieve size of 120/160 meshes / cm. Zirconium disks were placed on top of the cylinder in the cup and the arrangement was then placed in the pressure chamber of the above-described device for generating high pressures and high temperatures at a pressure of 55 kilobars exposed and then heated for 54 minutes at a temperature of 1550 C. After cooling, the pressure was turned off and a composite cylinder was removed. One end face of the cylinder was polished on a diamond lapping device to expose the core made of cubic boron nitride Microscope with 300x magnification showed that the bond between en the cubic boron nitride crystals and also with the hard metal outer jacket. It is to be expected that a die arrangement formed using this cylinder is particularly well suited for drawing steel or tungsten wire, since in this case the lower chemical reactivity of the cubic boron nitride compared to diamond can be advantageous.

Example 7

In a cemented carbide cylinder made of 87% by weight WC and 13% by weight Co a hole with a diameter of 3.56 mm was machined. The cylinder had an outside diameter of 8.81 mm and a Length of 3.18 mm. The cylinder was placed in a zirconium cup with a wall thickness of 0.05 mm. In the lower part of the ZyKn

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the holes became a layer of a tungsten carbide-cobalt powder mixture (87 wt.% WC, 13 wt.% Co) lightly tamped down. On the The tamped powder mixture then became a diamond single crystal suitable as a wire drawing die with a thickness of approximately 1.78 mm and an average diameter of 3.30 mm and then placed another powder mixture around and over the diamond crystal, and using a small hand press with a

2 compressed average pressure of about 7 kg / mm.

This arrangement was then sheathed with sheet zirconium with a thickness of 0.05 mm and placed in the above-described device for producing introduced by high pressures and high temperatures. The loading arrangement was a pressure of 55 kilobars and one Exposed to a temperature of approximately 1550 C for approximately one hour. After cooling to 30 ° C., the pressure was switched off and the composite cylinder taken. The adhering zirconium and the cemented carbide covering the top and bottom of the diamond crystal was removed with a fine jet of abrasive. The partially exposed diamond crystal appeared clear and intact, despite his The surface was slightly matt, suggesting that the surface was etched from a minor reaction with the surrounding metal was. Thickness measurements on the embedded diamond crystal showed that the loss of diamond was negligible.

The outer wall of the composite cylinder was then ground to a conicity of 2% so that one end had a diameter of 6.41 mm and the other end a diameter of 6.35 mm. The composite cylinder was then pressed into a ring made of the alloy Ren6 41, which had a correspondingly conical central opening and a thickness of 7.92 mm and one

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Outside diameter of 22.4 mm. The ring consisting of the alloy Rene "41 was fitted with a snug fit into a protective ring made of stainless steel with an outer diameter of 25.4 mm. A force of approximately 770 kg was used to press the conical cylinder into the ring made of the alloy Rena 41 the compressive stress exerted on the cylinder

2
to about 84 kg / mm sc

in Fig. 6 shown shape.

2
estimated at about 84 kg / mm. The finished arrangement had the

After making a draw hole, the finished arrangement was put together with several other similarly constructed arrangements for drawing tungsten wire having a diameter in the range used from 0.18 to 0.30 mm.

409840/0792

Claims (11)

PATENT CLAIMS: / 1. * Wire drawing die, characterized by a core mass with a centrally arranged, double-conical through hole, which is predominantly made of diamond, cubic boron nitride or a polycrystalline Mixture of diamond and cubic boron nitride consists, and at least one hard metal mass, which directly with is connected to the core mass and encloses it while forming a symmetrical support and which is predominantly made of tungsten carbide, Titanium carbide, tantalum carbide or a mixture of these carbides and cobalt, nickel, Contains iron or a mixture of these metals, and further characterized in that the interface between the core mass and the cemented carbide mass is free of cavities and irregular and toothed over a range of 1-10Ou. 2. Wire drawing die according to claim 1, characterized in that that the core mass consists predominantly of polycrystalline diamond. 3. Wire drawing die according to claim 1, characterized in that that the core mass is a single diamond crystal. 4. wire drawing die according to claim 1, characterized in that that the core mass consists predominantly of polycrystalline cubic boron nitride. - 28 - 409840/0792 5. wire drawing die according to claim 1, characterized in that that the core mass has essentially the shape of a cylinder and the hard metal mass has the shape of this cylinder owns enclosing jacket. 6. wire drawing die according to claim 5, characterized in that the composite body consisting of the cylinder and jacket Has the shape of a truncated cone. 7. wire drawing die according to claim 1, characterized in that that the composite body consisting of core mass and hard metal mass with a press fit in an annular body having high tensile strength sits. 8. wire drawing die according to claim 7, characterized in that that the outer wall of the composite body permanently under a 2 compressive stress of at least approximately 7 kg / mm. 9. wire drawing die according to claim 7, characterized in that the ring body consists of metal. 10. Wire drawing die according to claim 1, characterized in that the composite body consisting of the core mass and the hard metal mass has the shape of a truncated cone. 11. wire drawing die according to claim 1, characterized in that that the core mass of the Hart m · ^ aI I mass both laterally as is also enclosed peripherally. 409840 / i ^if> 2