Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
1999-09-27
2001-02-13
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S296000, C051S307000, C051S308000, C051S309000, C451S540000, C451S541000, C451S548000, C451S552000
Reexamination Certificate
active
06187069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wheel used for the cutting, grooving, polishing, grinding and the like of various materials.
2. Description of the Related Art
Ceramic materials such as alumina and silicon nitride have recently been employed as precision parts of electric devices and the like in increasing quantities. Accordingly, there is an increasing demand for high accuracy in the fabrication of these materials, which are difficult to grind.
A metal bond wheel or a resin bond wheel provided with super abrasive grains such as CBN or diamond grains is typically used for the fabrication of such difficult-to-grind materials.
In a metal bond wheel, super abrasive grains are held in a dispersion arrangement or dispersed in a metal bond phase that contains a single kind of metal or alloy. Because the metal bond phase is hard, the metal bond wheel is hardly worn by friction with the work or is hardly chipped, and is therefore excellent in wear resistance. On the other hand, however, a very strong holding force of grains leads to a poor self-edging function, in which super abrasive grains projecting from the surface of the metal bond wheel gradually fall off and are replaced by fresh super abrasive grains. This results in the deterioration of sharpness at the tips of the super abrasive grains, which become dull under the effect of wear.
In a resin bond wheel, super abrasive grains are held in a dispersion arrangement or dispersed in a resin bond phase that contains, for example, a thermosetting resin. The resin bond phase has excellent self-edging properties, permitting a longer duration of a satisfactory sharpness. However, the resin bond wheel suffers from early wear and insufficient strength, prevent high-speed wheel or high-speed cutting.
There is therefore a demand for a composite bond wheel which has both the excellent wear resistance of a metal bond phase and the excellent self-edging properties of a resin bond phase, in a good balance.
To cope with such a demand, various improvements have been suggested over the conventional metal bond wheel and the conventional resin bond wheel.
The aforementioned improvements in the conventional art will now be described with reference to
FIGS. 4 and 5
.
FIG. 4
is an enlarged sectional view illustrating a typical metal bond wheel. In this metal bond wheel
1
, super abrasive grains
3
including, for example, diamond abrasive grains are held in a dispersion arrangement by a metal phase
4
including, for example, Ni in a grain layer
2
. A phenol resin, for example, is baked onto the surface of the metal phase
4
and is covered with a resin phase
5
, and the super abrasive grains
3
are exposed on the resin phase
5
.
FIG. 5
is an enlarged sectional view illustrating a typical resin bond wheel. In this resin bond wheel
6
, super abrasive grains
8
including, for example, diamond abrasive grains are held in a dispersion arrangement in a resin bond phase
9
including, for example, a resin such as a polyimide resin in a grain layer
7
. In the resin bond phase
9
, mixed metal powder including, for example, copper and tin serving as a metal filler
10
is added in a dispersion arrangement.
In the metal bond wheel
1
, described above, having a soft resin phase
5
formed through baking onto the surface of the metal phase
4
, the resin phase
5
is worn out by friction with the work or by chipping, and at the point when the wear of the super abrasive grains
3
causes a deterioration of sharpness, grains fall off the resin phase
5
, and self-edging functions cause fresh super abrasive grains
3
to project from the surface of resin phase
5
.
The resin phase
5
is provided, however, only on the surface of the metal phase
4
. If wear of the resin phase
5
proceeds and the resin phase
5
disappears completely, there would remain only the metal phase
4
holding the super abrasive grains
3
with the metal alone, thus leading to a deterioration of the self-edging properties. Therefore, when the metal bond wheel
1
is used for the fabrication of a hard and brittle material, for example, the resin phase
5
disappears at an early stage, resulting in the deterioration of the finished surface quality of the workplace.
In the resin bond wheel
6
described above, the particles of metal powder added as the metal filler
10
to the resin bond phase
9
are individually isolated, and no bonding state is formed between metal particles. This resin bond wheel
6
is therefore poor in improving the wear resistance of the resin bond phase
9
against friction with the work or chipping, and it has been heretofore impossible to prevent rapid wear, which is a defect of the resin bond wheel.
SUMMARY OF THE INVENTION
The present invention was developed in view of the aforementioned circumstances, and one object of the present invention is to provide a wheel which maintains satisfactory sharpness with self-edging upon cutting, grooving or polishing various works, and which is excellent in wear resistance.
These and other objects of the invention have been solved by the present invention, the first aspect of which provides a composite bond wheel having a grain layer with abrasive grains and a bonding phase which includes a metal and a resin, wherein the abrasive grains are dispersion-arranged in the metal; wherein pores opening outside are dispersion-arranged in the metal; and the wherein pores are filled with the resin.
In the composite bond wheel of the first aspect of the invention, in which the pores opening outside are dispersion-arranged, the bonding phase is more easily worn out as compared with a bonding phase formed with only the metal as in the conventional metal bond wheel, thus causing easy occurrence of falling out of the abrasive grains and self-edging. Further, because of the dispersion arrangement of the pores over the entire metal, it is possible to maintain satisfactory sharpness since self-edging occurs repeatedly upon grinding.
The pores are filled with the resin. Elasticity is therefore imparted to the abrasive grains projecting from the surface of the composite bond wheel, particularly as compared with the case where the abrasive grains are held by the metal alone. It is thus possible to desirably alleviate mechanical impact between the work and the abrasive grains during grinding and to reduce scratches on the ground surface of the work or chipping produced on the cut surface thereof.
The metal in the first aspect of the invention has a crosslinked structure, and metal particles are bonded together with no isolated portion. A stronger force holding the abrasive grains is therefore available as compared with the case of holding grains with the resin alone as in the conventional resin bond wheel. This results in a higher wear resistance against friction with the work or chipping, thus extending the service life of the wheel. Further, because of its good thermal conductivity and high strength, the wheel of the invention is applicable, for example, as a sharp-edge wheel or a thin-edge blade.
In the composite bond wheel of the second aspect of the invention, the aforementioned metal includes cobalt.
In the composite bond wheel of the second aspect, the metal includes cobalt (Co): when forming a metal having pores opening outside by sintering a metal powder containing cobalt, sintering does not take place on the outer surfaces of the cobalt powder particles, resulting in relatively many non-reacting portions. It is therefore possible to increase the volume of pores contained in the metal after sintering, and adjust the volume of pores by acting on the amount of the cobalt powder.
In place of or in addition to cobalt serving as a porous constituent, the metal may preferably include, for example, nickel, iron, zinc or copper, and further, may contain tin or silver as a bonding constituent.
In the composite bond wheel of the third aspect of the invention, the pores account for 5 to 60 vol. % relative to the total volume of the grain layer.
In the composite bond wheel of the third
Hoshi Junji
Ikeda Yoshitaka
Sawada Yoshihiro
Suzuki Ken'ichi
Marcheschi Michael
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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