WO1997043092A1

WO1997043092A1 - Abrasive tool and method for making same

Info

Publication number: WO1997043092A1
Application number: PCT/BE1997/000048
Authority: WO
Inventors: Thierry Gillet; Théodore Holsteyns
Original assignee: Diamant Boart, Societe Anonyme
Priority date: 1996-05-13
Filing date: 1997-04-22
Publication date: 1997-11-20
Also published as: SK151798A3; NO985256D0; DE69718789D1; NO985256L; AU2376597A; TW340081B; HUP9901499A3; ATE231770T1; EP0907463A1; BE1010166A6; NO311414B1; KR20000010841A; PL329845A1; CZ363898A3; JP2000510054A; TR199802292T2; HUP9901499A2; EP0907463B1; PL183417B1

Abstract

An abrasive tool for cutting, drilling, milling or the like, including a diamond grain positioning structure (2) attached to the circumference of a holder (6). A skeleton with open pores (12) in the outer surface thereof is provided in said structure (2) at least in the portion adjacent to said circumference of the holder (6), and said pores preferably occupy at least 30-75 % of the apparent volume of said portion. The average pore diameter is of 100-500 microns, with a maximum of 2 mm, and the holder (6) essentially consists of a metal or alloy (5) filling at least 70 % of said pores (12) and having a melting point higher than the working temperature of the tool and lower than 950 °C.

Description

Abrasive tool and method of manufacturing the tool.

The present invention relates to an abrasive tool, for cutting, drilling, grinding or the like, in particular of a building material, comprising a structure positioning diamond grains fixed to the periphery or surface of a rigid support essentially consisting of a molded, cast, injected or pressed material, penetrating at least partially into interstices or pores provided in said structure. It is more particularly an abrasive tool of the type as described in the international patent application PCT / BE95 / 00101.

The present invention relates more particularly to particularly advantageous embodiments of abrasive tools falling within the general scope of the aforementioned international patent application.

To this end, according to the invention, this structure is present, at least in its zone near the aforesaid periphery of the support, in the form of a skeleton comprising open pores opening into the external surface of the latter and preferably occupying at least 30 to 75% of the volume appearing in this zone, the average diameter of these pores being between 100 and 500 microns, with a maximum of 2 mm, the support essentially consisting of a metal or an alloy penetrating into at least 70% of these pores and having a melting point above the temperature of use of the tool and below 950 ° C. Advantageously, according to the invention, the support is essentially based on one of the elements: zinc, tin, aluminum, magnesium or copper or an alloy of these elements, such as an alloy containing silicon. The invention also relates to a particular method for manufacturing the abovementioned abrasive tool. This process is characterized by the fact that the diamond grains are positioned three-dimensionally at a certain distance from each other according to an annular structure in a mold in which the support for this annular structure is formed, in such a way as to obtain , at least in the zone of the latter near the support, pores distributed substantially uniformly between these diamond grains, preferably forming from 30 to 75% by volume of the apparent volume of this zone, whether a metal is poured or an alloy from which the support is made and having a melting point higher than the temperature of use of the tool and lower than 950 ° C., in the liquid state, in this mold so that this metal or alloy penetrates in at least 70% of these pores and that this metal or alloy is then solidified, thereby forming an intimate and substantially homogeneous link between the annular structure positioning the diamond grains and support. Other details and particularities of the invention will emerge from the description given below, by way of nonlimiting example, of some particular embodiments of an abrasive tool and of a method of manufacturing the latter with reference to the accompanying drawings.

Figure 1 is a schematic view, partial and in cross section, of a sintering mold in which is formed an annular structure positioning diamond grains. Figure 2 is a perspective view of such an annular structure showing over a part of its length the positioning of the diamond grains. Figure 3 is, on a larger scale, a detailed view of diamond grains positioned in an annular structure according to a first embodiment of the invention. Figure 4 shows, on a larger scale, a second embodiment of the positioning of diamond grains in the annular structure according to Figure 2. Figure 5 shows schematically a cross section of part of a casting mold containing a abrasive tool formed of a structure positioning diamond grains and a support fixed to this structure.

Figure 6 is a partial sectional view of a molded part. Figure 7 is a partial sectional view of the molded part after machining.

Figure 8 is a sectional view of the molded part after machining and grinding forming a finished abrasive tool. Figure 9 is also a sectional view of part of an abrasive tool of another embodiment than that shown in Figure 8, before grinding.

Figure 10 is a perspective view of a drill having an annular structure positioning diamond grains according to the invention.

Figure 11 is also a perspective view of a grinding wheel having a structure positioning the diamond grains according to the invention. In the various figures, the same reference numbers relate to identical or analogous elements.

The present invention relates, in general, to an abrasive, cutting, drilling, grinding or similar tool comprising a rigid or rigid structure positioning, in a three-dimensional manner, diamond grains at a certain distance from each other. of others and which is fixed on a support with which it forms a very intimate and rigid link.

This structure, which will be called below

"diamond structure", is present, at least in its area near the support, in the form of a skeleton comprising open pores opening at least partially into the external surfaces of this skeleton and preferably occupying at least 30 to 70% of the volume appearing from this area. The average diameter of these pores is generally between 100 and 500 microns with a maximum of 2 mm. The support, for its part, essentially consists of a metal or an alloy penetrating at least 70% of these pores, so as to allow a very solid bond to be formed between the structure and the support. Furthermore, this support has a melting point sufficiently above the temperature of use of the abrasive tool to avoid any deterioration of the latter during its use. In addition, according to the invention, this melting temperature must be less than 950 ° C. to allow the penetration of this metal or alloy into the pores of the skeleton without risk of deterioration of the diamond grains incorporated in the diamond structure.

Thus, according to the invention, the support is essentially based on one of the elements: zinc, tin, aluminum, magnesium or copper or an alloy of these elements, such as an alloy containing silicon.

Excellent results have been obtained with an abrasive tool, the support of which is formed from an aluminum-silicon alloy containing 5 to 9% of silicon, preferably of the order of 7%.

According to a particular embodiment of the invention, the aforementioned structure is formed by particles made up of diamond grains coated with a metallic envelope and assembled together in a three-dimensional manner by sintering. Such particles can be obtained by the application of techniques known per se, as for example described in the patent in the United States of America No. 3,316,073, more particularly in column 2, lines 29 to 49 and in the example. 1 of this patent.

It should however be noted that the invention is not limited to the use of particles obtained according to such a specific process.

Advantageously, the aforementioned diamond structure comprises from 1 to 15% by volume of diamond grains, preferably of the order of 3%, maintained in a skeleton essentially based on cobalt, iron, bronze or nickel.

This diamond structure can, in certain cases, be doped with grains of another abrasive material, such as grains of silicon carbide, aluminum oxide or silicon, for example, at a rate of at most ten times the volume of the quantity of diamond grains. For the manufacture of an abrasive tool as described above, it is first arranged to obtain diamond grains positioned three-dimensionally at a certain distance from each other in an annular structure in a mold, in which a support is then formed for this annular structure, in such a way as to obtain, at least in the region of the latter near the support, pores distributed between these diamond grains, preferably forming from 30 to 75% by volume of the apparent volume of this zone. In a subsequent step, the metal or alloy intended to form the support is poured in the liquid state into this mold so that this metal or alloy can penetrate at least 70% of these pores. Finally, this metal or alloy is solidified, thus forming an intimate link between the annular structure and the support clinging to these pores and possibly at least partially enveloping the latter. The casting of the metal or of the alloy can advantageously be carried out in a permanent mold, that is to say in refractory steel, in the sense described in "Metals Handbook, Vol. 5, Forging and Casting p. 265 et seq. (By the ASM Committee on production of Permanent Mold Casting), published by the American Society for Metals ".

The invention will be further illustrated below by an example relating to the manufacture of a cutting disc for masonry materials. As shown in FIG. 1, firstly, in a first mold 1, an annular structure 2 is positioned positioning diamond grains 3.

Next, this diamond structure 2 is placed in a second mold 4, as shown in FIG. 5, into which the material 5 intended to form the support 6 is introduced in the liquid state.

More particularly, for the formation of the annular structure 2, particles 7 are introduced into an annular cavity 9 of a first mold 1, as shown for example in detail in FIG. 4, which are formed of diamond grains 3 coated with a metal casing 8. This annular cavity 9 in which these particles are thus stacked is delimited externally and laterally by a hoop 10 and above by an annular bearing piece 11 exerting, by its weight, a certain pressure on these particles 7 The latter are heated, under a controlled atmosphere, in an oven at the sintering temperature of the metal or of the alloy of which the casing 8 is made, so as to obtain a surface fusion of this casing 8 and thus, upon cooling. Subsequent to mold 1, the formation of a porous rigid skeleton, as shown diagrammatically in FIG. 2.

Instead of making use of diamond grains 3 pre-coated with a metal casing 8, as shown in FIG. 4, it is advantageous to start from a mixture of diamond grains with a metal powder of cobalt, of iron, bronze and / or nickel, in a proportion of 1 to 15% by volume of diamond grains and preferably of the order of 3% by volume, relative to the volume of the metal powder. This mixture is then poured into the annular cavity 9 of the mold 1 which is heated until a partial or surface fusion of this powder is obtained. The latter, under the weight of the support piece 11, agglomerated to form a porous coherent mass. FIG. 3 shows, on a relatively large scale, this agglomerated powder 8 which traps the diamond grains 3 distributed beforehand in a substantially homogeneous manner in this powder.

Both in the case of a particle structure 7 assembled by sintering, as shown in FIG. 4, as in the case of a powder premixed with diamond grains and agglomerated by sintering, as shown in FIG. 3, it is possible to therefore obtain a structure positioning the diamond grains in a three-dimensional manner between which pores 12 are formed, distributed in a substantially homogeneous manner.

Example

This example relates to the manufacture of a cutting disc for masonry materials with a diameter of 200 mm and a thickness of 3.5 mm which can be used on a portable sawing machine ("angle grinder") dry that is to say without water cooling.

Diamond grains with a particle size between 20 and 80 mesh (ANSI B74-16) were previously mixed with a cobalt powder with a particle size of 1 to 5 microns at a proportion of 3% by volume of diamond. The mixture thus obtained was poured into the annular cavity 9 of a first mold 1 of refractory steel (FIG. 1) with a depth of 3.5 mm and a width of 1.25 cm, so as to obtain a headband continuous circular of constant thickness of this mixture. This strip was then subjected to a certain pressure by the support piece 11 with a weight of 4 kg.

In a following stage, this mold was brought to a temperature of 800 ° C. in an oven with a nitrogen atmosphere for 30 minutes so as to allow, by sintering, to obtain the agglomeration of the powder in the form of a porous structure.

After demoulding, the annular structure thus obtained had a regularly distributed residual porosity of the order of 60%, with pores with an average diameter of 300 microns and a maximum of 1 mm.

This diamond structure 2 thus obtained was then placed in a second mold 4, as shown in FIG. 5. It was a permanent mold in refractory steel intended for the casting of a metal or a liquid alloy under gravity. This metal was formed from an aluminum-silicon alloy with a silicon content of 7% and an addition of 3% of copper, which had a melting point of the order of 600 ° C. A quantity of 25 kg of this alloy was melted in an electric oven maintained at a temperature of the order of 670 ° C. The molten alloy was deoxidized and refined so as to reduce its content of oxides and hydrogen gas in order to obtain the finest crystalline grain possible during solidification in the mold 4. This alloy was poured in the center of the mold 4, by means of a crucible, not shown, with a capacity of 1 kg through a nozzle 13 with a diameter of 50 mm fixed in the center of the mold, at its upper part, so to ensure perfect filling of the mold and infiltration into substantially all the pores of the diamond structure 2.

This mold 4 was maintained at a temperature of 250 to 300 ° C and was lubricated, prior to cûûée, using a release agent known per se based on silicone. The alloy filled the mold 4 at the rate of 300 gr., The rest, that is to say 700 gr., Was kept in the nozzle 13 and exerted a pressure on the quantity of the alloy introduced into the mold . The nozzle 13 containing the remainder of the alloy, which, after solidification, is called "counterweight", was disconnected, by cutting, during demolding, from the abrasive disc obtained. This demolding was carried out when the temperature of this part had gone down to about 150 ° C. Figure 6 shows the part thus removed from the mold, then, when this part had reached room temperature, it was finished by machining, in particular turning and milling, and a bore 14 of 30 mm was drilled along its axis, as shown in FIG. 7. Finally, the diamond-shaped annular structure of the abrasive disc thus machined, provided with this bore, was surface treated by grinding to expose the diamond grains partially, as shown in figure 8.

According to a particular embodiment of the invention, use is made of a single mold 4, as shown in FIG. 5, which can undergo rotation around its axis.

Particles of coated diamond grains, previously agglomerated or not, are introduced into this mold 4 by its center or its axis, more particularly by the nozzle 13, while the latter rotates around its axis at a speed sufficient to cause displacement of these particles by centrifugation towards the periphery of the mold, in the annular cavity 9. Then, in the subsequent stage, which has already been mentioned above, the material 5 intended to form is introduced in the liquid state the support 6, in the mold 4, also through the center or the axis of the latter and this while it rotates at a sufficient speed to that, also by centrifugation, this liquid material 5 propagates towards its periphery and penetrates into the pores 12 remaining between the particles or to the agglomerates of particles. This operation is then followed by cooling of the mold, so that the material 5 solidifies by forming a rigid support which is intimately bonded with the particles enveloping the diamond grains extending at the periphery of this support and therefore constituting the aforementioned diamond structure 2.

Finally, the diamond disc thus obtained is removed from the mold.

It should be noted that the dimensions of the diamond structure 2 can vary between relatively wide limits.

However, for a cutting disc of masonry material, preference is given for a thickness of 2.5 to 3.7 mm (0.1 to 0.15 inch) and a width of between 2.5 mm and 1.75 cm, depending on the desired tool life.

The method according to the invention has the advantage, among other things, of not having to print any pressure on the diamond structure during its assembly with the support, contrary to what is the case in conventional methods for producing diamond tools. This advantage makes it possible to considerably reduce the costs of manufacturing diamond tools.

In addition, the metallic substance, in particular the alloy, used for fixing the diamond structure to the support is identical to that which constitutes the support itself, which avoids any tension between this structure and the support.

In certain cases, it may be useful to reinforce the support 6 of the abrasive tool by incorporating a metallic network 15 into the latter, as shown in FIG. 9. The abrasive tool can also consist of a drill, as shown in FIG. 10, of a grinding wheel, as shown in FIG. 11 or of a cable having, at regular distances, abrasive blocks formed around the latter. . These blocks are in fact small cylindrical grinding wheels which have at their cylindrical wall a diamond structure of the same type as that of a diamond disc for example. The technique applied for the manufacture of these three types of abrasive tools is identical to that for the manufacture of a disc, as illustrated in FIG. 5 or described above.

In fact, it suffices simply to adapt the shape and dimensions of the mold or molds used.

Furthermore, in certain cases, the porosity of the diamond structure 2 may not be homogeneous but for example vary from zero porosity, in the end zone opposite to that oriented towards the support, to an average porosity in the zone intermediate between this end region with zero porosity and that close to the support, at maximum porosity in the latter region.

The porosity of the intermediate zone can for example vary from 10 to 30%, while the porosity of the zone of the diamond structure close to the support is preferably from 30 to 75% in order to allow effective attachment between this structure. and support.

The zone close to the support can for example form a quarter or half of the total volume of the diamond structure, while the end and intermediate zones can for example have an identical volume.

It should however be noted that these zones are generally not well delimited since the variation of the porosity from one zone to the neighboring zone preferably takes place in a substantially continuous manner. Thus, a porosity gradient can occur in each of these zones. For example, in the intermediate zone, this porosity may be minimal on the side of the end and maximum zone on the side of the zone located near the support.

In yet another embodiment of the diamond structure according to the invention, the positioning of the diamond grains can be carried out on a frame or a lattice with regular meshes, for example with a diameter of 1 to 5 mm, made of steel, made of bronze or synthetic fibers.

Finally, the diamond-shaped annular structure may have a geometry with a grooved or grooved profile, thus making it possible to increase the rigidity of the fixing of this structure to the support by at least partial filling of the surface hollows thus presented by such a structure. The abrasive proportion contained in the diamond annular structure can be very variable depending on the intended use of the abrasive tool. This proportion is however preferably between 1 to 15% in apparent volume of this structure, as already mentioned above.

It is understood that the invention is not limited to the embodiments described above but that many variants can be envisaged without departing from the scope of the invention.

Claims

1. Abrasive, cutting, drilling, grinding or similar tool, comprising a structure (2) positioning diamond grains and fixed to the periphery of a support (6), characterized in that this structure (2) is present at least in its zone near the aforesaid periphery of the support (6), in the form of a skeleton comprising open pores (12) opening into the external surface of the latter and preferably occupying at least 30 to 75% of the apparent volume of this zone, the average diameter of these pores (12) being between 100 and 500 microns, with a maximum of 2 mm, the support (6) essentially being made of a metal or an alloy (5) penetrating at least 70% of these pores (12) and having a melting point greater than the temperature of use of the tool and less than 950 ° C.

2. Tool according to claim 1, characterized in that the support (6) is essentially based on one of the elements: zinc, tin, aluminum, magnesium or copper or an alloy of these elements, such as an alloy containing silicon.

3. Tool according to claim 2, characterized in that the support (6) is formed from an aluminum-silicon alloy containing 5 to 9% of silicon, preferably of the order of 7%.

4. Tool according to any one of claims 1 to 3, characterized in that the aforementioned structure (2) comprises particles (7) formed by diamond grains (3) coated by a metal casing (8), these particles (7) being assembled three-dimensionally by sintering.

5. Tool according to any one of claims 1 to 4, characterized in that the above-mentioned structure (2) comprises from 1 to 15% by volume of diamond grains (3), preferably of the order of 3%, maintained in a skeleton essentially based on cobalt, iron, bronze or nickel.

6. Tool according to any one of claims 1 to 5, characterized in that the skeleton (2) incorporating the diamond grains (3) is doped with grains of another abrasive material at the rate of at most ten times the volume of the quantity of diamond grains (3).

7. A method for manufacturing an abrasive tool, in particular according to any one of claims 1 to 6, comprising an annular structure (2) positioning diamond grains and fixed to the periphery of a support (6), characterized in that the diamond grains (3) are positioned three-dimensionally at a certain distance from each other according to an annular structure (2) in a mold (4) in which the support for this annular structure (2) is formed, in such a way as to obtain, at least in the region of the latter near the support (6), pores (12) distributed substantially uniformly between these diamond grains (3), preferably forming from 30 to 75% in volume of the volume appearing from this zone, in that a metal or an alloy is poured, of which the support (6) is made up and having a melting point higher than the temperature of use of the tool and lower than 950 ° C, in the liquid state, in this mold (4), d e so that this metal or alloy (5) penetrates into at least 70% of these pores (12) and in that this metal or alloy (5) is then solidified thereby forming an intimate and substantially homogeneous bond between the annular structure (2) positioning the diamond grains (3) and the support (6).

8. Method according to claim 7, characterized in that first of all, in a first mold (1), the aforementioned annular structure (2) positioning the diamond grains (3) and, in that this structure (2) is then placed in a second mold (4) into which the metal or the alloy (5) is introduced in the liquid state intended to form the support (6) and to penetrate into the pores (12) of this structure (2).

9. Method according to claim 8, characterized in that, for the formation of the abovementioned annular structure (2), particles (7) formed of diamond grains (3) coated with a layer are introduced into the first mold (1) metal shell (8), and in that these particles (7) are subjected to sintering so as to thus form a skeleton (2) having 30 to 75% of open pores (12), this skeleton (2) then being placed in the second mold (4) in which the metal or alloy (5) is poured intended to form the support (6) and to penetrate into the pores (12) of this skeleton (2).

10. Method according to claim 8, characterized in that, for the formation of the abovementioned annular structure (2), diamond grains (3) are mixed beforehand, in a substantially homogeneous manner, with a metallic powder (8) , preferably cobalt powder, in a proportion of 1 to 15% by volume of diamond grains, this mixture then being introduced into a mold (1) and subjected to sintering so as to agglomerate this powder (8) by trapping the grains of diamond (3), the particle size of this powder (8) being chosen so as to obtain, after sintering, a structure (2) comprising from 30 to 75% by volume of pores (12).