Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
2000-08-11
2002-05-07
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S296000, C051S307000, C051S309000
Reexamination Certificate
active
06383238
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a resin bonded abrasive tool particularly useful, for example, for mill grinding of hard and brittle.
The disclosure of Japanese Application No. H11-230909, H11-246748, and 2000-038653 is hereby incorporated by reference into the present application.
2. Description of the Background
Generally, resin bonded abrasive tools are produced by the following method. The raw powders of thermosetting resin, such as, for example, an epoxy resin and phenol resin, are mixed with the super abrasive grains of a diamond and CBN, etc. This mixture is molded independently, or with a base metal if needed. Then, it is pressed and sintered. The result is a resin bonded abrasive tool having a super abrasive grains layer.
When the grinding is performed to comparatively hard work materials, the resin bonded phase holding super abrasive grains is crushed or worn out. Super abrasive grains drop out rather than decrease in sharpness by the wear in a tip of the super abrasive grain, because, in resin bonded tool, the resin bonded phase holding the super abrasive grains is comparatively elastic and brittle. Therefore, although resin bonded tools are susceptible to intense wear, clogging on a surface of grinding and a decrease in sharpness of a super abrasive grain due to wear are not common. Thus, resin bonded tools are able to perform grinding efficiently as compared with metal bonded tool, etc. Moreover, the damage to work materials is small and the finished surface is good, due to the elastic effect of the super abrasive grains held by resin bonded phase. Therefore, it has the advantage of being used for the grinding where small surface roughness such as mill grinding of work materials of semi conductor wafer for example is required. By the way, in the conventional resin bonded tool, solid lubricant, such as hBN and graphite for example, is dispersed inside of the resin bonded phase as filler in order to control the frictional heat generated by grinding resistance.
For example, in resin bonded tool
1
shown in
FIG. 9
, diamond abrasive grain
4
dispersed inside of resin bonded phase
3
consisted of phenol resin as grain layer
2
. Solid lubricant
5
such as CaF
2
(calcium fluoride), etc. is added and further distributed. In case of the grinding by using these resin bonded abrasive tool, the solid lubricant
5
inside of resin bonded phase
3
has a function as lubricant in omitting one by one with resin bonded phase
3
and abrasive grain
4
and aids smoothly performed grinding by a super abrasive grain
4
. The solid lubricant
5
may also aid in controlling the friction heat of grain layer
2
and work material.
OBJECT OF THIS INVENTION
However, although cutting resistance can be reduced by the addition of solid lubricant which is distributed as filler in resin bonded abrasive tool of above mentioned composition, the problem remains that the life of abrasive tool is short by the reason that the binder phase of resin is brittle. Also, increasing the wear resistance of abrasive particle layer is difficult to achieve. This invention aims at offering resin bonded abrasive tool which can raise wear resistance and reduce the grinding resistance.
SUMMARY OF THE INVENTION
In order to attain the purpose which solves the above mentioned subject, the resin bonded abrasive tool of this invention is characterized by distributing amorphous carbon in the above mentioned resin binder phase in resin bonded abrasive tool which comes to distribute super abrasive particle in resin binder phase. The amorphous carbon (also referred to as “glassy carbon”) has the characteristics that the bending strength is at about 16 kg/mm2, a value about 5 times to graphite (“also referred to as “crystal carbon”). Also, the compressive strength is at about 120 kg/mm2, a value about 20 times greater than for graphite. The modulus of elasticity is about 3 times greater than for graphite, and the shore hardness Hs is at about 110, a value about 3 times greater than for graphite. Here, the binder phase of resin bonded abrasive tool is made, for example, from phenol resin, the modulus of elasticity of the phenol resin is at about 7×102 kg/mm2, The rate of modulus of elasticity of abrasive particle layer of resin bonded abrasive tool can be raised by adding and distributing amorphous carbon in resin binder phase of resin bonded abrasive tool. This can raise the compressive rigidity of abrasive particle layer. Also, the abrasive particle layer can carry out compressive deformation by grinding resistance at the time of grinding, or it can prevent super abrasive particle from being buried into resin binder phase even where the super abrasive particle projects from the surface of abrasive particle layer and forms the cutting tooth of resin bonded abrasive tool which receives the grinding resistance. Further, the mechanical strength of abrasive particle layer holding super abrasive particle can be raised. Furthermore, the amorphous carbon distributed in resin binder phase acts as lubricant, can reduce the grinding resistance between work materials, and can control the generation of grinding heat. In addition, for example, it can control more effectively the deformation of resin bonded abrasive tool, or the wear of the tool because the hardness, compressive strength and bending strength of amorphous carbon is large compared with solid lubricant such as graphite. Furthermore, the resin bonded abrasive tool in this invention has the characteristics that the above mentioned amorphous carbon is the shape of spherical type. In above mentioned resin bonded abrasive tool, spherical amorphous carbon can raise the compressive strength of resin binder phase, and it also relieves the stress which acts to the abrasive particle layer at the time of grinding machining.
Moreover, as the spherical amorphous carbon exposed from the surface of abrasive particle layer contacts the grinding surface of work materials, the frictional resistance is small and the generation of frictional heat is suppressed small even if the friction with the work materials arises. Moreover, if the resin binder phase which holds spherical amorphous carbon on the surface of abrasive particle layer is worn out and approximately half grade of the whole volume of the spherical amorphous carbon comes to project from the surface of abrasive particle layer, this amorphous carbon will be omitted from the surface of abrasive particle layer, and a tip pocket will be formed in the position where the amorphous carbon was held. That is, compared with non uniform shape particles by which unevenness was formed, for example, on the outside surface, amorphous spherical carbon promotes a decrease in the holding force by resin binder phase and omission from resin binder phase. The discharge ability of scraps improves in that the grinding liquid is introduced at the time of grinding machining or grinding waste etc. enters into the formed tip pockets.
On the other hand, as the amorphous carbon is spherical, the compressive strength is high compared with non uniform type, the grinding load and the deformation by grinding can be controlled, and it can prevent effectively burying into the resin binder phase of super abrasive particle which exists in the outside surface. Furthermore, the mobility and formability of raw materials can be raised in case that the abrasive particle layer is formed. Furthermore, the resin bonded abrasive tool has the characteristics that the above mentioned amorphous carbon is non uniform shape.
In resin bonded abrasive tool mentioned above, particularly, in case that the minute amorphous carbon is dispersed in resin binder phase, the spherical amorphous carbon is in the tendency of dropping out from resin binder phase. The holding force can be raised by using the amorphous carbon of non uniform shape. Furthermore, the resin bonded abrasive tool in this invention has the characteristics that the amorphous carbon of the above mentioned non uniform shape results from grinding spherical amorphous
Nakamura Masato
Takahashi Tsutomu
Takano Toshiyuki
Marcheschi Michael
Mitsubishi Materials Corporation
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