DE2805460A1 - TOOL PART AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

Tool part and process for its manufacture

The invention relates to a tool part, in particular a tool insert Made of abrasive particles such as diamond and cubic boi nitride for fitting cutting tools.

It has been found that according to the teaching of the US PS 3,745,623 and US Pat. No. 3,609,818, the diamond body produced is only of limited use because it can be used at temperatures of over suffers about 700 C damage. Similarly, it has been found that a body made of cubic boron nitride and manufactured according to the teaching of US Pat. No. 3,767,371 and US Pat. No. 3,743,489 is also only of limited use, since it is also at temperatures suffers damage of over approximately 700 C. The use of

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Deutsche Bank Munich. Account no. 82/08050 (BLZ70070010)

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like body is therefore not possible where (1) for fastening of the body on a base requires a brazing alloy with a melting point close to or above the temperature at which the body is thermally damaged, or where (2) embedding the body in a wear-resistant one having a high melting point Matrix is required, which is the case, for example, with a drill bit used for drilling rock, its surface is usually equipped with cutting inserts.

The invention is based on the object of creating a temperature-resistant tool part, in particular a cutting insert.

This object is achieved by a tool part which, according to the invention is characterized by

a) self-bonded particles of diamond or cubic boron nitride which are between approximately 70 and 95 percent by volume of the tool part make up, and

b) a network of interconnected empty pores that make up between approximately 5 and 30 percent by volume of the tool part and are dispersed in this and are defined by the particles and a metallic phase between approximately 0.05 and 3 percent by volume of the tool part and which is a sintering aid for the abrasive mass.

The one consisting essentially of self-bound abrasive particles and a network of interconnected tool parts containing dispersed distributed pores is produced by a mass of abrasive particles into a self-bonded body using a sintering aid material at high pressures and Temperatures are directly linked to one another. The under

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Bodies formed under the influence of high pressures and temperatures contain self-bound, i.e. directly connected to one another Particles and is interspersed with the sintering aid material, for example cobalt or cobalt alloys. The sintering aid material is then removed, for example by immersing the body in aqua regia. It turned out that by removing of substantially all of the sintering aid, an abrasive body which has a significantly improved resistance to thermal decomposition at high temperatures having.

Another embodiment designed as a layered body, the in a manner similar to the first embodiment discussed above can be produced, consists essentially of a layer of self-bonded abrasive particles and one to this Layer bonded base preferably made of cemented carbide.

The invention will now be explained in more detail with reference to the drawing, which is a photomicrograph of an area of a ground surface shows a diamond body produced according to the invention.

The grinding surface shown in the drawing refers to a diamond body, but can just as well be used to explain the alternative embodiments of the invention, in which the abrasive particles consist of cubic boron nitride (CBN).

The body shown in the drawing contains diamond particles 11, which make up between 70 and 95 percent by volume of the body. With particles here is a single crystallite or a fraction of one

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Crystallites meant. The self-bond is at the interfaces 13 seen from adjacent particles 11, i.e. diamond-diamond bond between adjacent particles 11. The diamond crystals 11 lying in the cut surface shown in the drawing are also bound to neighboring diamond crystals (not visible) in the third dimension. The body is of one metallic phase made of auxiliary sintering metal (not shown in the drawing) penetrated substantially uniformly. One takes indicates that the metallic phase in due to neighboring diamond particles formed, enclosed areas is encapsulated. The metallic phase comprises between about 0.05 and 3 percent by volume of the body. A network of interconnected empty pores 15 is dispersed and distributed over the entire body is through the diamond particles 11 and the metallic phase (not shown). The pores 15 comprise between about 5 and 30 percent by volume of the body.

According to one embodiment, the body only consists of self-bound particles. According to another embodiment, the body is bound to a base (not shown) which preferably consists of tungsten carbide-cobalt-cemented carbide.

The diamond particles 11 expediently have a particle size in the range of 1-1000 microns. For cubic boron nitride particles, a particle size is in the range between 1-300 micrometers useful.

A preferred method for producing a tool part according to the invention comprises the following process steps:

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a) A Mass of diamond particles or CBN particles and a mass of a material given that the sintering together of diamond particles or CBN particles existing mass enables or * favors,

b) the reaction vessel and its contents are simultaneously exposed to temperatures in the range of 1200-2000 C and pressures of over 40 kb,

c) the supply of heat to the reaction vessel is switched off,

d) the pressure on the reaction vessel is removed,

e) the abrasive body formed by process steps a) - d) is removed from the reaction vessel, which consists of self-bound, i.e. particles that are directly bonded to one another and a metallic phase, which consists of the particles that have penetrated into the abrasive body Sintering aid material is formed, and

f) the metallic phase that has penetrated the body becomes im substantially completely removed, so that the metallic phase remaining in the body is only about 0.05 to about 3 percent by volume of the body.

The term "simultaneously" used in process step b) means that the action of high pressures and high temperatures occurs at the same time, but this is not necessary, that the exposure to the high pressure and the high temperature will start or stop at the same time, although this may also be possible can.

The term "sintering aid" as used herein means a Material that acts as a catalyst for diamond and / or promotes the sintering of CBN. It is not known in what way (catalytically

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or in another way) the sintering aids the self-binding of Promote or favor CBN (CBN-CBN bond).

Preferred embodiments of the method steps listed above a) to e) for producing a diamond body from diamond particles are disclosed in US Pat. No. 3,745,623 and US Pat 3 609 818 explained in more detail.

Diamond bodies are according to these patents under the Exposure to high pressures and high temperatures produced at which the hot, compressed diamond particles with a catalyst material which penetrates axially or radially into the diamond particle mass and penetrates. While This penetration and infiltration process catalyzes sintering of the diamond particles, which leads to an extensive diamond-diamond bond leads. The catalyst material used is one of those already described in US Pat. No. 2,947,609 and US Pat

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2 947 610, namely _A a catalyst metal in elemental form from the group comprising the metals of group VIII of the periodic table, chromium, manganese and tantalum, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable non-catalyst metals , (3) an alloy of at least two catalyst metals, or (4) an alloy of one or more catalyst metals and one or more non-catalyst metals. The catalyst used is preferably cobalt in elemental form or in the form of an alloy. The catalyst material forms a metallic phase in the abrasive body formed under the action of high pressures and high temperatures, as has already been mentioned in process step e).

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Preferred embodiments of process steps a) to e) for Manufacture of a tool part from CBN particles is explained in US Pat. No. 3,767,371. According to Example 1 of US Pat. No. 3,767 CBN bodies are produced under high pressures and high temperatures by an infiltration process in which CBN particles are involved a molten sintering aid material (cobalt metal), which is swept axially through the CBN particles will. During this infiltration or flooding process there is a sintering of the CBN particles, which leads to an expanded GBN-CBN bond leads. Other materials suitable as sintering aids for CBN are alloys made of aluminum and an alloy component from the group comprising nickel, cobalt, manganese, iron, vanadium and chromium, as described in US Pat. No. 3,743,489 is shown in column 3, lines 6-20. Cobalt and cobalt alloys however, are preferred. The auxiliary sintering material forms the Explanation of process step e) mentioned metallic phase.

In an embodiment of the invention in which process steps a) to e) according to US Pat. No. 3,745,623 and US Pat. No. 3,767,371 and US Pat. No. 3,743,489, a composite body is obtained which by bonding a layer of abrasive particles (made of diamond or GBN) in situ on a substrate made of cemented carbide. The source used for the auxiliary sintering material is preferably that provided for forming the sintered hard metal base Material (either in the form of a powder mixture or a preformed body). For more details regarding the document is referred to US-PS 3,745,623, in particular column 5, line 58, to column 6, line 8, and column 8, line 57, to column 9, line 9.

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In another embodiment of the invention, a body is obtained from essentially self-bound abrasive particles. at In this embodiment, method steps a) to e) are carried out in the same way as explained above, with only the material provided for forming the cemented carbide substrate for the layer of abrasive particles in the form of a powder mixture or a preformed body is preferably omitted. In this case, the auxiliary sintering material is added separately, for example in the manner described in U.S. Patent 3,609,818. Of course, after removal of the metallic Phase (method step f) are fixed by brazing on a base made of cemented carbide or another material to create a body or insert for equipping a tool.

According to the invention, the metallic phase is removed from the body by acid treatment, extraction with liquid zinc, electrolytic removal or similar processes, so that a body of essentially 100% abrasive particles remains in self-bound form. The remaining body contains essentially no or hardly any metallic phase. In the case of the previously known bodies with a metallic phase, the inadequate temperature resistance can theoretically be explained by the fact that the metallic phase catalyzes the conversion of the direct bonds between the abrasive particles and / or breaks the direct bond between the particles as a result of the thermal expansion of the metallic phase. It has been found that the body according to the invention, which is essentially free of metallic phase, can withstand temperatures of up to 1200-1300 ° C. without noticeable thermal damage occurring.

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The invention will now be explained in more detail on the basis of exemplary embodiments.

example 1

Disc-shaped diamond bodies were made by (1) a 1.4 mm thick layer of fine diamond particles with a particle size of less than 8 micrometers and a disc with a thickness of 3.2 mm and a diameter of 8.8 mm made of cemented carbide (13% by weight Co, 87% by weight WC) inside a zirconium container with a thickness of 0.05 mm, (2) several of these containers in a reaction vessel of the one shown in FIG. 1 of US Pat. No. 3,745,623 type shown above were stacked, (3) the reaction vessel loading a pressure of about 65kb and a temperature of about 1400 C for 15 minutes, (4) slowly first the temperature and then the pressure was reduced and (5) the samples were ground after removal from the reaction vessel were, which resulted in bodies which had a 0.5 mm thick diamond layer, which on a 2.7 mm thick cemented carbide layer was bound. This was followed by surface sleeping the cemented carbide layer removed from each body.

As indicated in Table I, half of the samples were subjected to a leaching treatment in hot concentrated acids, to remove the metallic phase and other other soluble non-diamond substances. To remove the infiltrated material two different treatment methods were used. From a first group comprising Samples A-1 through A-4 were samples A-3 and A-4 only with a hot mixture of acids concentrated nitric acid and concentrated hydrofluoric acid in the

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ratio 1: 1 treated. For a second, samples B-1 to B-4 In the comprehensive group, samples B-3 and B-4 were treated with hot aqua regia (concentrated hydrochloric acid and concentrated sulfuric acid in a ratio of 3: 1). It turned out that when using aqua regia the leaching is considerable happened faster. Samples A-3 and A-4 were leached for 8 to 12 days, while Samples B-3 and B-4 were between 3 and Were leached for 6 days. In both cases, the dimensions of the samples did not change during the acid treatment and no splitting of diamond could be found either. Since diamond is not dissolved by acids, they are at the Weight loss occurring during acid treatment can be attributed to the removal of the metallic phase.

Before the leaching, the proportion of the metallic phase present in the samples was approximately 8.1% by volume or 19.8% by weight. calculated (based on density measurements of the samples before leaching and the raw materials used to make them). After leaching, approximately 0.5 percent by volume or 0.2 percent by weight of the metallic phase remains. The distance from to to 90 wt.% of the metallic phase (sample B-4) also indicates that the metallic phase is mainly in a coherent Pore network is located. When examining a fracture surface of a leached sample with a scanning electron microscope it was found that the pore network runs over the entire diamond layer. The pores are distributed over the entire diamond layer and most of the pores are less than a micrometer in diameter. This suggests that the acid is covering the entire diamond layer penetrated and causes a substantially uniform removal of the metallic phase from the diamond layer Has.

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As indicated in Table I, the flexural strength (deflection at break) and the modulus of elasticity of the diamond layers were also measured. The strength test was performed with a three-point loading device, in which two roll steel were arranged on a base, was during a third steel roller axially parallel rolls in the middle above the two steel provided to these. The samples were centered over the lower rollers and loaded until they broke. The elongation of the samples was measured parallel to the tensile stress with the aid of strain gauges which were connected to a strain gauge. Samples A-1 to A-4 were prepared for the strength test by finishing their surfaces with a diamond wheel (diamond particles with a particle size of 177-250 micrometers). Samples B-1 through B-4 were machined on a lapping machine using diamond lapping powder with a particle size of 15 microns in preparation for the strength test to achieve a better surface finish than Samples A-1 through A-4 was possible by grinding. It is assumed that the better polished surfaces in the samples lapped with diamond powder result in higher strength values, since the surface has a higher quality, ie has fewer defects such as cracks or the like, on which stress concentration occurs when stressed. It can be assumed that the lower flexural strength values measured in the leached samples (A-3, A-4, B-3, B-4) are due to such surface defects.

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• - TS - (kg / mr (% Weight loss) 111 0 101 TABLE I. O 73 sample Removal of the metallic bending vessel " 16.1 87 see phase 16.2 129 0 143 A-1 0 88 A-2 17.0 81 A-3 17.9 A-4 B-1 B-2 B-3 B-4

Flexural strength modulus of elasticity (E) 3

(χ 10 kg / mm)

89 92

78 80

In contrast to the flexural strength values, the porosity has no influence on the measurement of the modulus of elasticity E (Table I), since the modulus of elasticity is a measure of the internal strength and rigidity of the material and does not depend on the formation of microcracks. After the infiltrated metallic phase has been removed from the samples, the modulus of elasticity is only reduced by approximately 12 %. This difference is due to the porosity of the leached samples, since the following applies to the modulus of elasticity E:

E = M

in which E = modulus of elasticity

M = moment

C = distance to the outer fiber

I = moment of inertia of the surface

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and M-C do not change, while I has decreased since the effective area has decreased proportionally to the porosity. Therefore, if it is assumed that the pores are in the form of spheres

M · C and are randomly distributed, E =, in which χ = the proportion

the porosity, so that the modulus of elasticity must be greater than the measured value of E. For the leached samples B-3 and B-4

3 2

a modulus of elasticity averaged 79 χ 10 kg / mm measured, so that taking into account the porosity correction

3 2

door the modulus of elasticity is 85 χ 10 kg / mm, which is only 5% lower than that measured on samples B-1 and B-2

3 2

Average value of 90 χ 10 kg / mm.

So the removal of the infiltrated metallic phase has one very little influence on the modulus of elasticity, from which it follows that the strength of the diamond layer is almost exclusively due to the diamond-diamond bond is due.

3 2

The modulus of elasticity of 90 10 kg / mm is only 10% lower

3 2

than the average value of 100 χ 10 kg / mm _s calculated from the elastic constants of a diamond single crystal.

Example 2

A diamond body was produced according to the manner explained in Example 1 for Samples A-1 to A-4, with only instead of the diamond particles with a part of cheng rosse from underneath 8 micrometers a diamond particle mixture of equal proportions of diamond particles with a particle size of 149 to 177 micrometers and diamond particles having a particle size of 105 to 125 micrometers were used.

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The composition of the body before leaching is calculated 89.1% by weight diamond (96.5% by volume) and 11.9% by weight metallic phase (4.5 percent by volume) · After leaching, the body had a total weight 11.5% less, so only 0.15% by weight of the metallic phase (0.06% by volume) remained in the body.

Example 3

Vi & r diamond bodies were produced according to Example 1. The cemented carbide was ground off each body. In two bodies, the infiltrated metallic phase was leached in hot acid mixtures of 1 HF: 1 HNO ₀ and 3-HCl :! ENT ₀ removed. All bodies were bonded to a round, tungsten carbide cemented carbide disk with a diameter of 0.89 cm by means of epoxy resin. The composite body thus formed was attached to a tool holder of a lathe and tested for wear resistance during turning. A rubber rod containing quartz sand as a filler was used as the workpiece. The following test conditions were used: surface speed 107-168 m / min (the maximum range within a group exposed to the same heat treatment was 24 m / min), sleek 0.76 mm, transverse feed 0.13 mm / per revolution, and test time 60 minutes. After testing, the samples were heat treated in a heating tube under a stream of dry argon gas. Treatment temperatures ranged from 700-1300 ° C with intervals of 100 ° C. The heat treatment time was 10 minutes at each treatment temperature. After each heat treatment, the samples were examined for damage with a scanning electron microscope and then, with the exception of the samples treated at 1000, 1100 and 1300 ° C., subjected to the wear test. After both the top and the

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If the lower edges were used as cutting edges, the edges were reground.

The results of the wear test are shown in Table II. The samples showed a fairly consistent behavior during the wear test. It turned out that the 700 C samples heat-treated for the first time compared to the samples not yet heat-treated have a lower wear resistance exhibit. The non-leached samples 3 and 4 showed no changes in wear resistance until between 800 and 900 C failed due to thermal damage. It turned out that the wear resistance as long as independent from the heat treatment until the diamond phase can no longer enclose the encapsulated metallic phase and cracking occurs. This behavior also indicates the presence of two distinct phases, namely the bound Diamond phase, which takes care of chip removal during testing, and the metallic phase, which is a remnant of the sintering process is. The leached samples 1 and 2 withstood the

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Heat treatment very good, even at 1200 C. At 1200 C. it persists the tendency to damage the sample slightly, suggesting that thermal reversal is beginning on the surface.

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TABLE II

Heat treatment
° c ■ Drained
Sample 1 sample 2 120-150 Not depleted
Sample 3 Sample 4 100-120 - - untreated 150-200 120 150 100 - - 700 150 100 120 100 - - 800 120 100 120 radial cracks 900 120 - 1000 - " - 1100 - 100-120 1200 86-100 1300

The test results listed in Table II are by the time per wear unit, with one wear unit corresponding to 0.25 mm. The tool wear was determined by measurement the width of the wear mark that was created on the cutting insert in engagement with the workpiece. The determined Data are only important with regard to the relative behavior of the leached and non-leached samples.

The leached samples gave a higher test value on average than the non-leached samples. This can be due to the fact that during the wear test the not worn out Samples are thermally damaged. Both during the wear tests As well as during the heat treatments, the same damaging effect can therefore occur. So if the engaged with the tool tip near the workpiece is heated to a high temperature, the cobalt phase expands more than the diamond phase, whereby at the tool tip within the foremost part

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layers of cracks appear. The damaged tool tip will weakened as a result and is therefore no longer as efficient. the However, leached samples are up to a higher operating temperature thermally stable and are therefore not thermally damaged when the workpiece is engaged.

Investigations with a scanning electron microscope showed that samples which had not been leached out were compared to samples which had not been leached out showed different behavior. In the case of samples that were not leached, the metallic phase emerge from the surface between 700 and 800 C, as could be ascertained with a 2000-fold magnification. After the temperature had been increased to 900 C, were of Cracks running radially towards the center of the specimen were found on the rounded cutting edge. The leached samples, however, remained up to about 1300 C relatively unchanged. The diamond layers were still clean after heat treatment at 1200 C, but were Taken after heat treatment at 1300 C with 20-fold magnification Photos out of focus and blurred and with 1000 times Photos taken at enlargement showed an etched surface with many exposed crystals. This may be due to thermal decomposition of the surface, but it can also be due to minor oxygen residues in the heat treatment furnace Be due to argon atmosphere.

Example 4

Two diamond bodies (samples IV-1 and IV-2) were made according to Example 1 produced, but the cemented carbide layer was not abraded. Sample IV-1 was epoxy resin (Epon 826 with methyl anhydride at the knots and benzyldimethylamine hardener)

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poured and hardened the epoxy resin. The surface of the diamond layer was then exposed by grinding the epoxy resin. Sample IV-1 was then held in a boiling mixture of 3HCl: 1HNO 2 for 37.15 hours. After removal from the acid mixture, the encapsulating resin of d r cemented carbide layer was removed. Visual inspection showed evidence of a minor reaction between the acid mixture and the unexposed surfaces. However, the surface of the carbide layer did not appear to have been noticeably attacked by the acid. The surface of the diamond layer was then examined with a scanning electron microscope (up to 2000 times magnification). The surface of the diamond layer had a similar appearance to the surfaces of the diamond layer of the leached samples according to Example 1. Sample IV-1 was then subjected to X-ray spectroscopic analysis to compare the intensities of the constituents of the metallic phase with those of a sample which had not been leached. The examinations carried out with a scanning electron microscope and the radiographic examinations showed that the acid had penetrated the diamond layer and had removed a substantial proportion of the metallic phase.

Samples IV-1 and IV-2 were then prepared in the same manner as in FIG Example 3 explains, tested for wear resistance. For the leached sample IV-1, a calculated according to Example 3 was obtained Wear value of 120-150, while a wear value of 100-120 was found for sample IV-2 which had not been leached out. These test results, from which the superiority of the leached sample can be seen, agree with those presented in Example 3 The results agree and therefore prove that removing the metallic phase in the area of the cutting edge increases the Performance of the diamond body is achieved.

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Claims (1)

PATENT CLAIMS E. T. tool part, characterized by a) self-bonded particles of diamond or cubic boron nitride which are between approximately 70 and 95 percent by volume of the tool part make up, and b) a network of interconnected empty pores that make up between approximately 5 and 30 percent by volume of the tool part and are dispersed in this and are defined by the particles and a metallic phase, which are between approximately 0.05 and 3 percent by volume of the tool part and which is a sintering aid for the particle mass. 2, tool part according to claim 1, characterized in that diamond particles are provided as particles and the metallic phase consists of (1) a catalyst metal in elemental form the group comprising the metals of group VIII of the periodic table, chromium, manganese and tantalum, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable non-catalyst metals, (3) one Alloy of at least two catalyst metals or (4) an alloy of one or more catalyst metals and one or more non-catalyst metals. 3. Tool part according to claim 1 or 2, characterized in that that the diamond particles have a particle size in the range of about 1 to 1000 micrometers. e0flÖ34 / flS94 _ ₂₀ _ 2805A6Ü 2 / 4. Tool part according to claim 1, characterized in that the particles consist of cubic boron nitride and the metallic ones which penetrate the tool part essentially uniformly Phase of cobalt, a cobalt alloy or an alloy of aluminum with nickel, manganese, iron, vanadium or chromium as Alloy metal consists. 5. Tool part according to claim 1 and 4, characterized in that the particles of cubic boron nitride have a particle size in the Have a range between 1 to 300 microns. 6. Tool part according to claims 1 to 5, characterized in that that the flexural strength of the tool part is at least approximately 2
35 kg / mm. 7. Tool part according to claims 1 to 6, characterized in that that the modulus of elasticity of the tool part is at least slightly 2
is about 50,000 kg / mm. 8. Tool part according to claims 1 to 7, characterized in that that the self-bound particles are bound to a base made of cemented carbide. 9. A method for producing a tool part according to the claims 1 to 8, where a) a mass of diamond particles or cubic boron nitride particles and a mass of sintering aid material for the respective particle mass are placed in a reaction vessel, b) the reaction vessel and its contents at the same time temperatures in Range of 1200-2000 C and pressures in excess of 40 kb ft fi 9 ß 3Ä / A S <U - 21 - c) the supply of heat to the reaction vessel is turned off, and d) from the reaction vessel of the process steps a) - c) formed abrasive body is removed, which consists of the particles directly bonded to one another and the sintering aid material floated between the particles, characterized in that the material washed into the body is substantially completely removed, so that the The proportion of this material remaining in the body is only about 0.05 to about 3 percent by volume of the body. 10. The method according to claim 9, characterized in that the particles are diamond particles and the sintering auxiliary material (1) is a catalyst metal in elementary form from the metals of group VIII of the periodic table, chromium, manganese and tantalum Group, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable Non-catalyst metals, (3) an alloy of at least two catalyst metals, or (4) an alloy of one or more Catalyst metals and one or more non-catalyst metals is used. 11. Method according to claim 9, characterized in that Particles of cubic boron nitride and, as a sintering aid material, cobalt, a cobalt alloy or an alloy of aluminum with a alloy metal consisting of nickel, manganese, iron, vanadium or chromium can be used. 12. The method according to claims 9 to 11, characterized in that that the metal is removed from the body by immersing the body in a Acid is removed. 909834/0594 - ²² - 13. The method according to claim 12, characterized in that the acid is aqua regia, nitric acid, hydrochloric acid and / or hydrofluoric acid is used. 14. The method according to claims 9 to 11, characterized in that that the metal is removed from the body by extraction with liquid zinc. 15. The method according to claims 9 to 11, characterized in that that the metal is removed from the body by means of electrolysis. 809834/0594