JPH02212074A - Diamond grindstone for cutting - Google Patents

Abstract

PURPOSE:To promote the spontaneous action of a diamond abrasive grain, meanwhile, to improve the wear resistance of a bonding agent and to improve the cutting property and efficiency by mixing the spontaneous promoting agent of the diamond abrasive grain consisting of a carbon grain or graphite grain into the bonding agent. CONSTITUTION:The spontaneous action of a diamond abrasive grain 3 is promoted by the carbon grain or graphite grain 4 mixed into a bonding agent 2 and the wear resistance of the bonding agent is improved as well. Consequently, the cutting property and cutting efficiency of a diamond grindstone 1 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diamond grindstone suitable for machining such as drilling and cutting.

[Conventional technology]

Diamond whetstones are attached to cutting edges, blades, etc. of power tools, etc., and are used for drilling and cutting work on concrete, rocks, asphalt, etc. Conventional diamond whetstones are made by using diamond abrasive grains, which serve as cutting abrasive grains, with a binder. It is mixed in a certain metal bond, and is manufactured by mixing methane bond and diamond abrasive grains, and then compressing and molding the mixture. Note that bronze-based, cobalt-based, tungsten carbide-based, iron-based, or the like is used for the metal bond.

[Problem to be solved by the invention]

The metal bond used in diamond grinding wheels has the function of holding diamond abrasive grains and the self-growth of diamond abrasive grains due to wear. During cutting, the metal bond constantly wears down, and a certain amount of diamond abrasive grains are always protruding from the surface of the grindstone due to its self-growth effect. If chips, etc. adhere to the outer periphery of the grinding wheel and the surface of the metal bond, and the amount of protrusion of the diamond abrasive grains disappears, it will become clogged, reducing cutting efficiency and becoming unusable. In this case, redressing becomes necessary and is a tedious task.

By the way, the metal bond that has a high ability to hold diamond abrasive grains has a dense structure, is hard, and has high wear resistance.Dungesten carbide powder is mixed in this metal bond, which reduces the lifespan of the cutting edge. We are trying to improve. However, since the metal bond has little wear, the amount of protrusion of the diamond abrasive grains that form the cutting edge is small, and the self-growth effect is poor, resulting in a decrease in cutting efficiency.

On the other hand, with metal bonds that have a low ability to hold diamond abrasive grains, such as brittle metal bonds, the diamond abrasive grains will easily fall off and have a short life. are in a contradictory relationship with each other, and it is difficult to reconcile them.

The present invention aims to eliminate the drawbacks of the prior art and provide diamond abrasive grains for cutting that can promote self-growth of diamond abrasive grains, improve the wear resistance of the binder, and improve machinability and cutting efficiency. purpose.

[Means to solve the problem]

The present invention is characterized in that a diamond abrasive grain self-growth promoter made of carbon grains or graphite grains is mixed into the binder.

[Effect]

In the present invention, the carbon grains or graphite grains mixed in the binder can promote the self-growth of the diamond abrasive grains and improve the wear resistance of the binder, thereby improving the cutting performance and cutting efficiency of the diamond whetstone. can.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged view showing a half cross section of the diamond grinding wheel for cutting according to this embodiment. In FIG. 1, diamond abrasive grains 3 are mixed in the metal bond 2 forming the diamond grinding wheel 1. In this embodiment, additives 4 such as carbon grains and graphite grains are mixed into the metal bond 2 in order to promote the independent action of the diamond abrasive grains 3. Additive 4
are randomly mixed among the abrasive grains 3, and similarly to the abrasive grains 3, they are firmly held by the metal bond 2.

The cutting edge of the diamond grinding wheel 1 is manufactured by mixing metal bond 2 made of metal or alloy powder and abrasive grains 3, adding an additive 4, pressurizing and molding. If the grain size is larger than , the additive 4 on the surface of the metal bond 2 will be destroyed during sharpening of the grindstone, and the metal bond 2 itself will also be destroyed, causing the abrasive grains 3 to fall off. When the particle size of additive 4 is equal to or smaller than that of abrasive grain 3, even if additive 4 is crushed or chipped during sharpening of the whetstone, it will have little effect on abrasive grain 3, and chip pockets will occur. This creates a good outlet for chips and prevents clogging.

In addition, the amount of the additive 4 is also related to the volume of the abrasive grains 3, but in particular, the volume ratio of the diamond abrasive grains 3 is 5 to 10%, and the amount of the additive 4 is
The sharpness is the best when 5 to 30% by volume is added.

In this case, the embrittled portion due to the carbon grains and graphite grains in the metal bond 2 is worn away during cutting, forming a type of chip pocket, which prevents clogging due to chips.

If the additive 4 is added in a volume ratio of 30% or more, chipping and chipping of the cutting edge will occur during sharpening, making it unusable, so it is necessary to suppress the volume ratio to 30% or less. On the other hand, when the volume ratio of additive 4 is suppressed to 5% or less, no such effect is observed. An example of a prototype is shown below.

Hereinafter, a prototype example of Sukiko will be explained with reference to FIG.

Prototype example-1 30/40 mesh of diamond abrasive grains 3 in metal bond 2 whose main component is bronze powder Cu-10wt%Sn.
The concentration level is 10, the particle size of the carbon particles is 40150 mesh, and the volume ratio is 5.10, 20, 30, 40.
The cutting edge was pressure-fired with the ratio changed to 50%. #1llll this
A plurality of pieces were fixed at equal intervals in an arc shape to the tip of a base metal 5 of a cylinder (diameter 80 wm). This diamond grindstone for drilling was attached to a hand-held power tool, and a concrete drilling test was conducted in a wet state. For comparison, a drilling test was also conducted under the same conditions without the addition of carbon particles. The drilling conditions were such that the depth of each drilling was 80°* and the number of tests was 100 times. Also, the pressing force at that time is 15-1 and the cutting speed is 250.
m/min.

The results are shown in the graph of FIG. 4, which shows the relationship between the drilling speed ratio, the wear volume ratio, and the amount of carbon particles added. In FIG. 4, the drilling speed of the diamond grindstone without carbon grains is expressed as 1, and the ratio thereof was determined.

As the amount of carbon grains added increased, the perforation speed increased as shown by dotted line A, but reached a maximum at a volume ratio of 20% and tended to decrease as the volume ratio increased.

Similarly to the drilling speed ratio, the wear volume of the cutting edge is expressed as 1 for a diamond grindstone without carbon grains, and as the amount of carbon grains added increases, the wear volume ratio increases as shown by the solid line B. When the carbon particles accounted for 40% or more by volume, the wear became so great that it could not withstand use.

From the above, considering the drilling speed of the diamond grinding wheel and the life of the cutting edge, the amount of carbon grains added should be 5% to 30%.
I came to the conclusion that % is good.

FIG. 3 is a partial bottom view of the diamond blade grindstone according to this embodiment, showing another prototype example according to this embodiment.

This prototype example will be explained below with reference to FIG.

Prototype Example-2 Bronze powder Cu-10wt%Sn, cobalt powder, iron powder, and tungsten carbide powder were mixed in a weight ratio of 1:1:1:1, and the particle size of carbon particles was 40150 mesh, and the volume ratio was Added 10%. Further, diamond abrasive grains were blended with a particle size of 35,150 mesh and a concentration of 20. This was pressurized and fired to form cutting blades, and a plurality of cutting blades were fixed at equal intervals around the outer circumference of a disc. This cutting diamond blade grindstone was attached to a hand-held power tool, and a concrete cutting test was conducted at a cutting speed of 406 m/min in a dry state. The cutting conditions were such that the cutting length was 150 m and the cutting length per cut was 0.5 m.

As a result, the cutting speed of the diamond blade grindstone with carbon particles added at a cutting length of 50 m was 2.0 times that of the diamond blade grindstone without additives. In addition, the effect of the additive was seen, being 1.8 times greater at a cutting length of 100 m and 1.5 times greater at a final cutting length of 150 m, the cutting speed was improved, and the sharpness was good.

On the other hand, regarding the wear of the cutting blade, there was almost no difference between the presence and absence of additives up to a cutting length of 80 m, and there was no problem even with a cutting length of 150 m.

In this embodiment, diamond is used as the abrasive grain 3, but the same effect can be obtained using cubic boron nitride BN abrasive grain.

As described above, according to this example, a highly tough part and a weak part coexist around the diamond abrasive grains mixed in the metal bond, so that the holding power of the metal bond is increased and at the same time By promoting the self-growth of diamond abrasive grains, machinability and cutting efficiency can be improved.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a diamond grinding wheel for cutting that eliminates the drawbacks of the prior art, promotes the self-growth of diamond abrasive grains, and improves the wear resistance of the binder to improve cutting performance and cutting efficiency. Can be done.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view showing a half cross section of a diamond grinding wheel for cutting according to an embodiment of the present invention, FIG. 2 is a bottom view of the cutting edge of a diamond core drill using the diamond grinding wheel of FIG. 1, viewed from the cutting edge. FIG. 3 is a partial bottom view of a diamond blade grinding wheel using the diamond grinding wheel of FIG. 1, and FIG. 4 is a graph showing the relationship between the drilling speed ratio, the wear volume ratio, and the amount of carbon particles added. 1 is a diamond whetstone, 2 is a metal bond, 3 is an abrasive grain,
4 is an additive 6 Name of patent applicant Hitachi Koki Co., Ltd.

Claims (1)

[Claims] 1. A diamond grinding wheel for cutting in which diamond abrasive grains are mixed in a binder, in which a diamond abrasive grain self-growth promoter made of carbon grains or graphite grains is mixed in the binder. A diamond grinding wheel for cutting. 2. Mixing carbon particles or graphite particles in a volume ratio of 5 to 30%,
The diamond grindstone for cutting according to claim 1, characterized in that the particle size is equal to or smaller than the particle size of diamond abrasive grains.