Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
  • B24D18/0009—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
  • B24D5/12—Cut-off wheels

Definitions

• the present invention relates to an abrasive tool for cutting, drilling, grinding or the like, in particular of a building material, comprising a structure at the periphery of a support essentially consisting of particles formed by diamond grains coated with a metal envelope having a melting temperature higher than that of the support and occurring 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 apparent volume of this zone.
• a tool according to the preamble of claim 1 and a method according to the preamble of claim 5 are known, for example, from US-A-3,779,726.
• the present invention relates more particularly to particularly advantageous embodiments of abrasive tools falling within the general framework of the aforementioned international patent application.
• the average diameter of these pores is between 100 and 500 microns, with a maximum of 2 mm, the support consisting of zinc, tin, aluminum, copper magnesium or of an alloy of these metals, such as an aluminum-silicon alloy, penetrating at least 70% of these pores and having a melting point above the temperature of use of the tool and below 950 ° C, the particles being assembled three-dimensionally by sintering so as to form a substantially rigid structure.
• the invention also relates to a particular method for manufacturing the abovementioned abrasive tool.
• 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.
• FIG. 4 shows, on a larger scale, a second embodiment of the positioning of diamond grains in the annular structure according to FIG. 2.
• FIG. 5 schematically represents a cross section of a part of a casting mold containing an abrasive tool formed of a structure positioning diamond grains and of 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.
• the present invention relates, in general, to an abrasive, cutting, drilling, grinding or similar tool comprising a rigid or made rigid structure positioning, in a three-dimensional manner, diamond grains at a certain distance from each other. of the others and which is fixed on a support with which it forms a very intimate and rigid link.
• diamond structure This structure, which will be called hereinafter “diamond structure”, is present, at least in its zone near the support, in the form of a skeleton comprising open pores opening at least partially into the external surfaces of this skeleton and occupying preferably at least 30 to 70% of the apparent volume of this zone.
• the average diameter of these pores is generally between 100 and 500 microns with a maximum of 2 mm.
• the support for its part, consists essentially 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.
• 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.
• 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 damaging the diamond grains incorporated in the diamond structure.
• 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 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.
• 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 by 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.
• 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.
• an abrasive tool 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.
• 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.
• annular structure 2 is positioned first, in a first mold 1, positioning diamond grains 3.
• 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.
• 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.
• mold 1 the formation of a porous rigid skeleton, as shown diagrammatically in FIG. 2.
• 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.
• 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 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 made of refractory steel (FIG. 1) with a depth of 3.5 mm and a width of 1.25 cm, so as to obtain a bandeau 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.
• 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.
• 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 .figure 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 with the aim of obtaining 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 casting, using a release agent known per se based on silicone.
• Particles of coated diamond grains 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.
• the dimensions of the diamond structure 2 can vary between relatively wide limits.
• 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.
• the metallic substance, in particular the alloy, used for fixing the diamond structure on the support is identical to that which constitutes the support itself, which avoids any tension between this structure and the support.
• 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 constitute in fact small cylindrical grinding stones which present 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.
• 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 bonding between this structure and support.
• the area near the support can for example form a quarter or half of the total volume of the diamond structure, while the end and intermediate areas can for example have an identical volume.
• 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.
• a porosity gradient can occur in each of these zones.
• this porosity may be minimal on the side of the end and maximum zone on the side of the zone located near the support.
• 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.
• 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.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Polishing Bodies And Polishing Tools (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=3889748

Family Applications (1)

Country Status (15)

Families Citing this family (2)

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• 1996
  • 1996-05-13 BE BE9600432A patent/BE1010166A6/fr not_active IP Right Cessation
• 1997
  • 1997-04-22 KR KR1019980708982A patent/KR20000010841A/ko not_active Withdrawn
  • 1997-04-22 AT AT97919209T patent/ATE231770T1/de not_active IP Right Cessation
  • 1997-04-22 WO PCT/BE1997/000048 patent/WO1997043092A1/fr not_active Ceased
  • 1997-04-22 TR TR1998/02292T patent/TR199802292T2/xx unknown
  • 1997-04-22 PL PL97329845A patent/PL183417B1/pl not_active IP Right Cessation
  • 1997-04-22 DE DE69718789T patent/DE69718789D1/de not_active Expired - Lifetime
  • 1997-04-22 AU AU23765/97A patent/AU2376597A/en not_active Abandoned
  • 1997-04-22 EP EP97919209A patent/EP0907463B1/fr not_active Expired - Lifetime
  • 1997-04-22 HU HU9901499A patent/HUP9901499A3/hu unknown
  • 1997-04-22 CZ CZ983638A patent/CZ363898A3/cs unknown
  • 1997-04-22 SK SK1517-98A patent/SK151798A3/sk unknown
  • 1997-04-22 JP JP09540321A patent/JP2000510054A/ja active Pending
  • 1997-05-01 TW TW086105801A patent/TW340081B/zh active
• 1998
  • 1998-11-11 NO NO19985256A patent/NO311414B1/no not_active IP Right Cessation

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