Abrasive tool making process – material – or composition – With inorganic material – Metal or metal oxide
Reexamination Certificate
1997-09-03
2001-01-23
Jones, Deborah (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Metal or metal oxide
C125S039000, C407S118000, C407S119000, C076SDIG001
Reexamination Certificate
active
06176888
ABSTRACT:
FIELD OF DISCOVERY
The invention relates to composite cutting bodies for abrasively processing hard materials or substrates where the cutting bodies or elements have a grain size of 400 &mgr;m to 1200 &mgr;m. Moreover, the invention also relates to a method for producing such composite cutting bodies.
BACKGROUND INFORMATION AND PRIOR ART
In many applications of working or disintegrating technology, tools are used, which have been hard-faced with diamond grains in order to improve the abrasive properties. For example, hollow drilling crowns, which are equipped at their front end with cutting segments, are used for producing boreholes or break-throughs of larger diameters. Wall saws and cutting-off wheels for cutting concrete, stone or ceramic are also hard-faced at their periphery with cutting segments. The cutting segments consist essentially of single diamond crystals, which are embedded in a metallic matrix. The grain size of the single diamond crystals, used for such cutting segments, is about 300 &mgr;m to about 600 &mgr;m. The single diamond crystals are not only disposed at the surface of the cutting segments, but are also distributed relatively uniformly over a portion of the height of the cutting segments. During the processing of the substrate, the edges of the single diamond crystals, protruding out of the surface of the matrix material, engage the material that is to be removed. If the single diamond crystals at the surface are lost, the matrix materials is worn away until new edges of single diamond crystals below are exposed.
In use, the edges can gradually become rounded or the single diamond crystals can break or fall completely out of the matrix material. Because of the relatively large grain size of the single diamond crystals, the number of effective cutting edges for the abrasive processing of the substrate is relatively small. If therefore a single diamond crystal drops out because of rounded edges or breakage or because it falls out of the matrix material, the cutting effectiveness of the cutting segments is impaired until the missing cutting edge is replaced once again by the exposure of a new single diamond crystal. This also has a disadvantageous effect on the achievable cutting speed of the cutting segment.
U.S. Pat. No. 4,591,364 discloses the use of diamond cutting bodies, which are agglomerated from diamond grains of a smaller grain size of typically about 70 &mgr;m to about 125 &mgr;m and predominantly a metallic binder material, for coating grinding disks. The mixture of diamond grains and binder material is sintered together in a sintering process to a 2-dimensional sinter cake. The 2-dimensional sinter cake is then broken up into small particles and screened. The screen fraction with an agglomerated grain size of about 149 &mgr;m to about 250 &mgr;m is used to coat the grinding disks. The breaking up of the sinter cake leads to a relatively large particle size distribution of the agglomerated composite cutting bodies, so that a not inconsiderable proportion of the agglomerates is either too large or too small for coating the grinding disks. Not only is the particle size of the rejected fractions quite different; due to the process of breaking the sinter cake, the geometric shape of the rejected fractions is also quite different There is also the danger that the fractions are damaged mechanically by the process of breaking. Therefore, at best, the rejected grain size fractions are ground further in order to be able to use them finally as grinding or polishing agents.
OBJECT OF THE INVENTION
It is an object of the present invention to provide composite cutting bodies, which have a narrow particle size distribution and also do not deviate significantly from one another with respect to their geometric shape. Waste is to be largely avoided during the further processing of the composite cutting bodies produced. The composite cutting bodies shall make it possible to produce cutting elements and cutting segments, which have a large cutting capacity, in the usual manner. It shall be possible to largely avoid losses in cutting effectiveness due to the rounding of protruding edges of the diamond grains and due to breakage or loss of diamond grains. In the event that such losses do occur, it shall be possible to compensate for them as soon as possible. It shall be possible to carry out the process of producing the composite cutting bodies as simply and as reproducibly as possible and to do so largely without mechanical damage to the composite cutting bodies due to additional breaking processes and without subsequent screening processes.
SUMMARY OF THE INVENTION
This objective is accomplished by composite cutting bodies, formed of diamond particles with a grain size in the range of 50 &mgr;m to 300 &mgr;m in a matrix of predominantly metallic binder where the cutting elements are agglomerated and sintered during an individual molding process from the mixture of diamond particles and binder material. The inventive method for their production comprises the steps forming a mixture of diamond particles in the size range of 50 &mgr;m to 300 &mgr;m and a metallic binder agglomerating the mixture into a composite, individually molding the mixture into a composite cutting element in a size range of 400 &mgr;m to about 1200 &mgr;m, and then sintering the composite cutting element. In particular, by means of the invention, a composite cutting body for the abrasive processing of hard materials or substrates, for example of concrete, is created, which comprises diamond particles embedded in a matrix of predominantly a metallic binder. The grain size of the diamond particles used is smaller than the grain size of the composite cutting bodies and is larger than 50 &mgr;m and smaller than 300 &mgr;m. Each composite cutting body is agglomerated and sintered in an individual molding process from a mixture of diamond particles and binder and has a grain size, which is about 400 &mgr;m to about 1200 &mgr;m.
Since each composite cutting body is produced in an individual molding process from the mixture of diamond particles and binder, the grain size and the shape of the composite cutting bodies can to some extent be controlled and the production process is largely reproducible. The composite cutting bodies, so produced, have a very narrow grain size distribution and resemble one another in their geometric shape. As a rule, therefore, all composite cutting bodies produced can be processed further. The grain size of the composite cutting bodies of about 400 &mgr;m to about 1200 &mgr;m corresponds largely to the grain size of the diamond crystals commonly used for the further processing of cutting segments. The composite cutting bodies can therefore be embedded in the usual manner in the matrix material. Since the composite cutting bodies consist of a plurality of small diamond particles linked to one another, many edges are available for the abrasive processing of the substrate. As a result, a rounding of individual edges, a fracture or a loss of a diamond particle has only an insignificant effect on the abrasive properties of the composite cutting body. The grain size of the diamond particles is larger than 50 &mgr;m and smaller than 300 &mgr;m. Understandably, fine grained diamond particles are used for composite cutting bodies of smaller grain size and the larger diamond particles are used for the larger composite cutting bodies. Not only are the diamond particles of smaller grain size less expensive than the larger single diamond crystals normally used, the diamond particles of smaller grain size usually also have fewer defects. As a result, the individual diamond particles have mechanical properties, which are better than those of single diamond crystals of larger grain size. This advantage is also transferred to the mechanical properties of the composite cutting bodies. The composite cutting bodies are produced directly without the process of breaking a sinter cake and a subsequent screening process. The omission of the additional processing steps simplifies the process of
Boretius Manfred Horst
Dorfmeister Johann
Magyari Eugen
Ritt Walter
Tillmann Wolfgang
Anderson Kill & Olick P.C.
Hilti Aktiengesellschaft
Jones Deborah
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