JPH08206962A - Conductive grinding wheel and its manufacture - Google Patents

Abstract

PURPOSE: To provide a conductive grinding wheel having both sufficient electric conductivity and strength. CONSTITUTION: In a grinding wheel, conductive nickel 24 is constituted on a surface of a binding agent 20 to bind abrasive grains 18 by being generated by heat decomposition of Ni3 B. Since such deposited nickel 24 forms a metallic layer on a surface of the binding agent 20, an addition quantity of the nickel 24 easily becoming a factor to reduce joining strength of the grinding wheel can be compratively reduced, the grinding wheel having both sufficient electric conductivity and strength can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive grindstone used for electrolytic polishing, electric discharge grinding, electrolytic electric discharge composite grinding and the like.

[0002]

2. Description of the Related Art Difficult-to-cut materials such as SUS steel and silicon nitride ceramics cannot obtain a good ground surface or high working efficiency by ordinary grinding. Therefore, in order to grind such a difficult-to-cut material, electrolytic polishing, electric discharge grinding, electrolytic electric discharge composite grinding, or the like is performed. These grinding processes are generally performed by applying a voltage between the grindstone and the work piece to generate an electric discharge or an electrolytic action, and the surface layer of the work material is changed to facilitate the grinding, and at the same time, the electric discharge action is performed. Since the grindstone is dressed at all times, high-efficiency and high-quality grinding is possible. Therefore, the grindstone used for this processing is required to have conductivity, and conventionally, a metal bond grindstone having conductivity in the binder itself has been mainly used.

[0003]

However, in grinding, a vitrified grindstone is often required because of the ease of truing and dressing and the fact that the work material is not limited. As a method of imparting conductivity to the vitrified grindstone, for example, there is a method of utilizing the porosity of the grindstone to perform electroless plating of nickel or the like on the internal pore surfaces after the bonding of the abrasive grains. However, even if conductivity is imparted in this way, peeling of the plating on the surface layer is likely to occur due to chips during the grinding process, so conductivity at the grinding point disappears and discharge or electrolytic action occurs in a relatively short time. It will be gone. Particularly, in the case of a grindstone using CBN abrasive grains, it is difficult to obtain the plating strength, so the above-mentioned inconvenience is remarkable.

Therefore, as a method for imparting conductivity to the vitrified grindstone, a metal oxide such as IrO ₂ , SnO ₂ , Ag ₂ O, which is easily reduced, is added at the time of mixing the abrasive grains and the vitrified bond, and this is used after firing. Technology for reducing
No. -41833), a technique of adding an organic compound in place of the above metal oxide and carbonizing the organic compound during firing (for example, Japanese Patent Publication No. 53-36638), or a part of the abrasive grains is Ti.
A technique (for example, Japanese Unexamined Patent Publication No. 62-264855) that uses a conductive material such as C has been proposed. However, these techniques have a problem that the strength of the grindstone becomes insufficient because the conductivity is insufficient and the binding force of the binder is impaired by the added metal or the like.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a conductive grindstone having both sufficient conductivity and strength.

[0006]

The first aspect of the present invention for achieving the above object is to provide a conductive material containing abrasive grains and a vitrified bonding agent binding the abrasive grains. It is a grindstone, and includes (a) a metal generated by thermal decomposition on the surface of the vitrified binder.

[0007]

In this way, the electrically conductive grindstone is constituted by heat-decomposing a metal on the surface of the vitrified bonding agent for bonding the abrasive grains. The metal thus formed forms a metal layer on the surface of the vitrified binder, and thus tends to cause a decrease in the bonding strength of the grindstone (a metal that does not form glass).
It is possible to obtain a conductive grindstone having both a sufficient conductivity and a sufficient strength, since the addition amount of can be relatively reduced. The generated metals are Ni (nickel), Fe (iron),
Mn (manganese), Mo (molybdenum), Nb (niobium), W
(Tungsten) or the like is preferably used. For example, it is mixed with a grindstone raw material in the form of a metal compound such as a boride that is decomposed by heat to generate those metals, and is fired to sinter the grindstone. As a result, it is generated in the above conductive grindstone.

Here, Ni is preferably used as the metal (b) generated in the grindstone. By doing so, Ni has higher conductivity than Mn and the like, and Nb,
Since it has better oxidation resistance and corrosion resistance than Mo, W, Fe, etc., it has the advantage that stable high conductivity can be obtained over a long period of time.

[0009]

A second aspect of the present invention for attaining the above object is to provide a conductive material containing abrasive grains and a vitrified bonding agent binding the abrasive grains. (C) The vitrified binder contains a rare earth metal hexaboride.

[0010]

In this way, since the rare earth metal hexaboride contained in the binder has conductivity and is easily dispersed in the vitrified binder, the strength of the grindstone is impaired. However, good conductivity can be obtained for the entire binder of the abrasive grains, that is, for the entire grindstone, and a conductive grindstone having both sufficient conductivity and strength can be obtained. As the rare earth metal hexaboride, various rare earth metal hexaborides such as LaB ₆ , CeB ₆ and YB ₆ can be used.

Preferably, in the first and second inventions, (d) the conductive grindstone has open pores,
A nickel plating layer is formed on the inner surface of the open pores. In such a conductive grindstone, the conductivity of the generated metal or rare earth metal hexaboride is supplemented by the nickel plating layer on the surface of the pores, so that the grindstone as a whole has higher conductivity.

[0012]

A third aspect of the invention for achieving the above object is a method for producing a conductive grindstone in which abrasive grains are bonded with a vitrified binder. A mixing step of mixing a grindstone raw material containing (e) a vitrified binder, a metal boride and abrasive grains, (f) a molding step of molding the grindstone raw material into a grindstone-generating shape having a predetermined shape, and (g) By firing the grindstone-forming form at a predetermined firing temperature, the abrasive grains are bound by the vitrified binder, and at the same time, at least a part of the metal boride is thermally decomposed to produce a metal element. , To include.

[0013]

In this way, the metal boride mixed in the grindstone raw material is thermally decomposed in the firing step to generate the metal element.
A layer of the produced metal is formed on the surface of the vitrified bond that binds the abrasive grains. Therefore, it is possible to obtain high conductivity even if the amount of the metal, which tends to decrease the bonding strength of the grindstone, is relatively small, and furthermore, the boron in the metal boride decomposed by heating is oxygen. As a glass component such as B ₂ O _{3 and the} like acts as a binder that contributes to the strength of the grindstone, the vitrified binder hardly reduces the bond strength. Therefore, a conductive whetstone having both sufficient conductivity and strength can be obtained. The metal borides include nickel borides such as NiB, Ni ₂ B and Ni ₃ B, FeB,
Iron borides such as Fe ₂ B, manganese borides such as MnB ₂ , molybdenum borides such as Mo ₂ B, niobium borides such as NbB and NbB ₂ , W ₂ B
Tungsten boride and the like are preferably used.

Preferably, (h) nickel boride is used as the metal boride. By doing so, Ni has a higher conductivity than Mn, and at the same time Nb, M
Since it has better oxidation resistance and corrosion resistance than o, W, Fe, etc., it has the advantage that stable high conductivity can be obtained over a long period of time.

Preferably, (i) Ni ₃ B is used as the metal boride. By doing this, Ni ₃ B becomes
Since the metal content is as large as 3: 1 in molar ratio, the amount of Ni produced during decomposition and production is large and the conductivity is excellent, while the amount of B produced is small and the binding strength of the vitrified binder is improved. There is an advantage that the reduction is suppressed.
Moreover, since the amount of B 2 generated is relatively small, the amount of metal boride added can be increased, and higher conductivity can be obtained.

Further, preferably, in the first to third inventions, the abrasive grains are diamond abrasive grains or C.
BN abrasive grains are used. In such a conductive grindstone, since the abrasive grains themselves have high grinding performance, it is possible to obtain a higher processing ability together with the electric discharge or the electrolytic action.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a conductive grindstone 1 according to an embodiment of the present invention.
It is a perspective view which shows 0. The conductive grindstone 10 is used for electrolytic polishing, discharge grinding, electrolytic discharge combined grinding, etc. in cylindrical grinding, surface grinding, roll grinding, etc., and has a mounting hole 12 at the center, for example, a disk made of steel. Core 14 and a plurality of substantially rectangular segment grindstones 16 fixed to the outer peripheral surface of the core 14 with a conductive adhesive such as silver paste.
The segment grindstones 16 are also bonded to each other with the same adhesive to increase the strength of the conductive grindstone 10. This segment grindstone 16 is formed, for example, by bonding superabrasive grains such as diamond grains and CBN grains with a vitrified binder to give, for example, a grain ratio of about 45 vol%,
It has a porosity of about 35 vol% and is manufactured as follows.

First, for example, glass frits (that is, vitrified binders) having the compositions shown in Table 1 below are pulverized and mixed in a pot mill to obtain glass powder having an average particle diameter of 3 to 10 μm. Then, for example, this glass powder 80v
ol% nickel boride (Ni ₃ B) powder (average particle size 4.19 μm)
Add 20 vol% and mix to obtain the binder. Furthermore, for example, 45 vol% of CBN abrasive grains (TYPE-I # 80 manufactured by GE), 20 vol% of the above-mentioned binder, and 10 vol% of a primary binder which is an organic adhesive such as dextrin are mixed to prepare a grindstone raw material powder. Prepare. This grindstone raw material powder is pressure-molded by using, for example, a hydraulic press device to obtain, for example, a substantially rectangular grindstone-generating body having a size of about 40 × 17 × 4 mm. Then, by grinding this grindstone-forming form, for example, at 900 ° C. in a nitrogen atmosphere, the abrasive grains are bonded by a vitrified binder,
The segment grindstone 16 shown in FIG. 1 is obtained. The firing temperature is appropriately changed depending on the composition of the vitrified binder. In this embodiment,
The above steps to the mixing step, the step to the molding step, and the step to the firing step.

[0020]

[Table 1]

As shown schematically in FIG. 2, the structure of the segment grindstone 16 is such that CBN abrasive grains 18 are bonded by a binder 20, and a large number of open pores are present between the abrasive grains 18. 22 is formed. As shown in FIG. 3 in which the vicinity of the abrasive grains 18 is further enlarged, Ni ₃ B is thermally decomposed in the above-mentioned firing step on the surface and inside of this binder 20 to form metallic nickel 24 in a layered form. Are provided with conductivity. Therefore, the segment grindstone 16 has a resistance value between the core 14 and the outer peripheral surface 26 of the segment grindstone 16 in a state of being fixed to the core 14,
For example, conductivity is given so that it becomes 1 Ω or less.
Note that, in FIG. 3, the nickel 24 is depicted as dispersed in an island shape, but most of the nickel 24 located on the surface of the open pores 22 is continuous on the surface of the binder 20 and inside. This imparts conductivity to the entire segment grindstone 16.

Here, according to the present embodiment, in the grindstone 10, as described above, conductive nickel 24 is formed on the surface of the binder 20 for bonding the abrasive grains 18 by thermal decomposition of Ni ₃ B. It is made to be composed. The nickel 24 thus formed forms a metal layer on the surface of the binder 20, so that the amount of the nickel 24 that is likely to be a factor that lowers the bonding strength of the grindstone 10 can be relatively small, and sufficient conductivity can be obtained. Thus, the grindstone 10 having both strength and strength can be obtained.

The nitrogen atmosphere at the time of firing is, for example,
For example, heating while flowing nitrogen gas into the firing furnace.
The atmosphere in which nitrogen and oxygen coexist.
Is. Therefore, the above Ni₃For example, the thermal decomposition reaction of B is
For example, 4Ni₃B + 3O₂→ 12Ni + 2B ₂O₃, Or Ni₃B →
 It is considered to be 3Ni + B, but due to the presence of oxygen,
It is estimated that at least some of the reactions occur. You
That is, Ni decomposed by heating₃At least the boron in B
Part of it combines with oxygen to become a glass component, increasing the strength of the grindstone.
As a contributing binder (ie as part of binder 20)
The strength of the segment grindstone 16 is sufficient
can get. Therefore, the conductive grindstone 10 is used for electric discharge grinding or
Suitable as a conductive grindstone for use in electro-composite grinding
And difficult-to-cut materials such as SUS steel and silicon nitride ceramics
When used for grinding, high quality processing with high efficiency
You can do it. In addition, the atmosphere at the time of firing, that is, nitrogen and acid
Elementary ratio is mixed Ni₃Various ratios depending on the amount of B, etc.
Is appropriately selected.

Further, since Ni is used as a metal that gives conductivity to the grindstone 10, it has higher conductivity than Mn which can be similarly produced by thermal decomposition, and N
Since it has better oxidation resistance and corrosion resistance than b, Mo, W, Fe, etc., it has the advantage that stable high conductivity can be obtained over a long period of time. Also, since Ni is added as Ni ₃ B, the metal content is as large as 3: 1 in molar ratio,
The amount of Ni produced during decomposition and production is high and the conductivity is excellent, while the amount of B produced is low and the binder 2
There is an advantage that the decrease in the bond strength of 0 is suppressed. Moreover, since the amount of B produced is relatively small, Ni ₃
The added amount of B can be increased, and higher conductivity can be obtained.

Further, in this embodiment, since the abrasive grains used for the segment grindstone 16 are CBN abrasive grains and the abrasive grains themselves have a high grinding ability, a higher machining ability can be obtained together with the electric discharge or the electrolytic action. To be

The mixing ratio of the Ni ₃ B powder (hereinafter, simply referred to as the mixing ratio means the mixing ratio of the metal boride to the glass powder) is determined by the following experiment. For example, in the above glass frit powder, the above
After mixing the Ni ₃ B powders at the ratios shown in Table 2, press molding is performed into a cylindrical shape of φ10 × 10 mm to prepare a test piece. Place one end face of this test piece on the upper side, heat at 900 ° C, cool,
The resistance value between two arbitrary points facing each other in the radial direction on the circumference of the end face was measured. In addition, the resistance value between two points corresponding to the above two points was measured for those that were melted and deformed during heating. The results are shown in the right column of Table 2. For the measurement of the resistance value, a tester with a full scale of 1 kΩ and a minimum scale of 1 Ω (for example, 3127 CLAMP ON Hi TESTER manufactured by HIOKI) was used, and “<1” in the table below indicates that it was below the measurement limit.

[0027]

[Table 2]

The segment grindstone 16 of the conductive grindstone 10 is
It is desirable that the resistance be low, and that its conductivity not deteriorate or become non-uniform from place to place during grinding. If the mixing ratio of Ni ₃ B powder is 5 vol% or more, the resistance value will be sufficiently low, 1 Ω or less, but there will be large variations at the measurement points, and in order to obtain a uniform resistance value, the mixing ratio should be 20 vol% or more. Is desirable. On the other hand, in the Ni ₃ B powder, boron is a glass component when it is decomposed by heat in the firing step to form metallic nickel, so that the bonding strength of the binder 20 is not easily reduced, and for example, the mixing ratio is 95 vol.
%, It has a strength that can withstand practical use, but the generation of such a glass component changes the composition of the binder 20. Therefore, in order to keep the bonding strength relatively high, the mixing ratio should be as high as possible. It is preferably low. Therefore, in the segment grindstone 16 of the present embodiment, the mixing ratio of Ni ₃ B is 2
About 0 vol% is appropriate.

On the other hand, in order to determine the composition of the glass frit capable of sufficiently maintaining the strength as the segment grindstone 16 in the above Ni ₃ B mixing ratio, glass frit powders of several kinds of compositions are prepared and the segment grindstone is prepared. Bending test pieces of 40 × 4 × 6 mm having the same abrasive grain ratio and the same porosity were prepared in the same manner as in No. 16, and their characteristics were compared. As a result, the resistance value between both end faces in the longitudinal direction was 1 Ω or less, and there was no big difference, and the three-point bending strength was the highest with the glass frit of the composition shown in Table 1 being about 50 MPa, and the conventional nickel plating made it conductive. The strength was the same as that of the whetstone that was given. The three-point bending strength was measured according to JIS R1601.

Next, another embodiment of the present invention will be described. In the following embodiments, the same parts as those in the above-mentioned embodiments are designated by the same reference numerals and the description thereof will be omitted.

A binder and a grindstone raw material were prepared in the same manner as in the above-mentioned embodiment, and a similar segment grindstone 16 was produced. However, the metal boride mixed when preparing the binder was lanthanum hexaboride (LaB ₆ average particle size 3.85 μm) in place of Ni ₃ B, and the mixing ratio was 40 vol%, for example.
The segment grindstone 16 is also used as the grindstone 10 by being fixed to the outer peripheral surface of the core 14 with a conductive adhesive or the like.

In this embodiment as well, although not as great as the above-mentioned embodiments, the grindstone 10 having both sufficient conductivity and strength.
was gotten. However, in the present embodiment, LaB ₆ itself has conductivity and cannot be thermally decomposed at the firing temperature (about 900 ° C.) of the segment grindstone 16 as described above, so that the LaB ₆ particles in the binder 20 are Exist in contact with each other. Then, the contact between the particles having the conductivity imparts conductivity to the entire segment grindstone 16.

The mixing ratio of LaB ₆ is determined by preparing a cylindrical test piece and measuring the resistance value in the same manner as in the above-mentioned embodiment. Formulation examples and measurement results are shown in Table 3 below. In order to use for electric discharge grinding or electrolytic discharge composite grinding, it is desirable that the resistance value of the grindstone 10 is as low as possible as described above. However, in general, when the segment grindstone 16 is fixed to the core 14,
If it is 1 kΩ or less, it can be sufficiently practically used, and for that purpose, the resistance value in the test piece may be several hundreds Ω or less. As shown in Table 3 below, it does not show conductivity at a mixing ratio of 20 vol%, but a resistance value of about several hundred Ω is added at about 25 vol%, and a practical value of 100 to 300 Ω at a mixing ratio of 40 vol%. However, if the mixing ratio is increased, the bonding force of the binder 20 is reduced and the strength of the grindstone 10 cannot be obtained. Therefore, the mixing ratio is desired to be as low as possible. Therefore, the mixing ratio is 40 vol% as described above.

[0034]

[Table 3]

Since LaB ₆ exists in the inside of the binder 20 in the state of mixed particles having a relatively large diameter without being decomposed by heat, the strength decrease when added in a large amount is the same as that of the above-mentioned embodiment. The grindstone has a mixing ratio of about 80 vol%.
When used as 0, it is a limit in terms of strength.

FIG. 4 shows that when the segment grindstone 16 is manufactured using the above Ni ₃ B or LaB ₆ , after the segment grindstone 16 is sintered, the inner surface of the pores 22 formed therein is plated with nickel, for example. It is the figure which showed typically the structure of the segment grindstone 30 with a plating layer in which the layer 28 was formed. Since most of the pores 22 are formed as open pores, the nickel plating layer 28 is formed even inside the segment grindstone 30. The nickel plating layer 28 is formed on the inner surfaces of the pores 22 by electroless plating, for example, by causing the nickel plating solution to flow through the segment grindstone 16 that has been subjected to pretreatment including degreasing.

In the grindstone 10 using the plated segment grindstone 30, when the nickel-plated layer 28 of the surface layer is peeled off by chips when used in discharge grinding or electrolytic discharge compound grinding, Nickel 2
The conductive thin film 4 or the binder 20 has conductivity, and the nickel plating layer 28 has higher conductivity inside. Therefore, as compared with the conventional conductive grindstone in which the abrasive grains are simply bonded with the vitrified bond and then plated, the segment grindstone 1 has high durability in the electric discharge grinding or the electrolytic discharge composite grinding.
It has a higher conductivity than that of 6. Therefore, in particular,
As in the case where LaB ₆ is used, in the segment wheel 16 having a relatively low conductivity in which the mixed metal boride is present in the binder 20 in its original form, the effect of applying the nickel plating layer 28 is high.

FIG. 5 shows that CBN abrasive grains 18 are mixed with LaB ₆ or a binder containing LaB ₆ as mentioned above, for example, in an amount of 2 to 3 vol%, and are fired at, for example, 900 ° C. and then crushed to form coated abrasive grains. For example, 45 vol% of the coated abrasive grains, 20 to 19 vol% of the glass frit powder, and 10 vol% of the primary binder are mixed and molded and fired in the same manner as the segment grindstone 16, and then Nickel-plated abrasive-coated segment grindstone 32 similar to the plated segment grindstone 30
It is a figure which shows the organization of typically. This segment grindstone 3
A coating 34 containing LaB ₆ is formed around the second abrasive grain 18, and the binder 36 binding the abrasive grain 18 is La diffused from the coating 34 of the abrasive grain 18 into the vitrified binder.
Is constructed contains B _6.

In the abrasive grain-coated segmented grindstone 32, the mutual conductivity of the nickel plating layer 28 on the inner surfaces of the pores 22 is enhanced by the coating 34 that coats the abrasive grains 18, and the LaB also exists inside the binder 36. _The diffusion of ₆ provides sufficient conductivity. Therefore, as well as having sufficient conductivity as in the above-mentioned embodiment, compared with the conventional, the wheel which is plated with nickel after simply binding with a vitrified binder, the conductivity when the nickel plating of the surface layer is peeled off. Is excellent in maintaining. Also, the binder 36
Since most of them are composed of a vitrified binder, a segment grindstone 32 having a higher strength can be obtained as compared with the case where the above binder is prepared by mixing LaB ₆ with glass frit.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in still another mode.

For example, as the metal boride mixed in the vitrified binder, not only one kind but also two or more kinds of metal boride may be used together in an appropriate ratio. For example, the two types of metal borides used in the above-mentioned examples are Ni ₃ B 10vol%, LaB ₆ 10v
Even if they are used together at a ratio such as ol%, each acts as described above and conductivity is obtained. In addition, among the metal borides, compounds that generate a metal by thermal decomposition similar to Ni ₃ B include other nickel borides such as NiB and Ni ₂ B, FeB and Fe.
An iron boride such as ₂ B, a manganese boride such as MnB ₂ , a molybdenum boride such as Mo ₂ B, a niobium boride such as NbB or NbB ₂ or a tungsten boride such as W ₂ B may be used, and As the rare earth metal hexaboride dispersed in the binder 20 and imparting conductivity to the binder 20 itself like LaB ₆ and LaB ₆ , various rare earth metal hexaborides such as CeB ₆ and YB ₆ are used. obtain. The amount and type of these metal borides are determined not only by the strength required for the grindstone 10 but also by the grinding conditions and the properties of the work material.

Further, although CBN abrasive grains 18 are used as the abrasive grains in the above-mentioned embodiment, the same effect can be obtained by using diamond abrasive grains, and there is some difficulty in the life of the grindstone. It is also applied to general abrasives as needed. The grain size of the abrasive grains is appropriately determined according to the application.

The composition of the glass frit as the binder is not necessarily limited to that described in the examples, but may be appropriately determined according to the strength required of the grindstone. For example, a glass frit having a composition shown in Table 1 in which a part of the composition is changed may be used.

The amount of nickel boride mixed in the binder is appropriately determined depending on the grinding conditions, the work material, the bond volume ratio of the grindstone, and the like.

Further, the mixing ratio of the metal boride may be reduced when the nickel plating 28 is also used. For example, in the case of NiB ₆ , if it is less than 20 vol% and in the case of LaB ₆ , it is possible to obtain a sufficiently high conductivity as the whole grindstone 10 even if it is less than 40 vol%. This is because in such a case, the conductivity from the core 14 to the vicinity of the surface layer of the segment grindstone 30 is secured by the nickel plating 28, so that it is sufficient to increase the conductivity for a short distance only near the surface layer.

In the abrasive grain-coated segment grindstone 32, the content of LaB _{6 in} the binder used for the coating 34 is 4
It may be more than 0 vol%. By doing so, the amount of LaB ₆ diffused from the inside of the film 34 into the binder 36 is increased, the conductivity is further improved, and the binder 36
Is still composed of a vitrified binder, so that the strength of the segment grindstone 32 is maintained.

In addition to steel, the core 14 may be made of carbon fiber reinforced resin, surface-plated fiber reinforced resin, or the like. The core 14 may have conductivity in addition to characteristics such as strength normally required as a grinding wheel.

Further, the conductive grindstone 10 is formed into a disc shape used for cylindrical grinding or the like by adhering the segment grindstone 16 to the outer peripheral surface of the metal core 14 in the above-mentioned embodiment. A grindstone, a cutting grindstone, or the like may be used, or a single segment grindstone may be used by being attached to a holder having a predetermined conductivity. When using the holder, the core 14 is unnecessary.

In the examples, the case where a metal such as Ni is formed in layers on the surface and inside of the binder 20 by thermal decomposition has been described. However, a continuous metal layer is formed on the surface of the binder 20. In that case, it does not matter if the metal layer is not formed therein.

Although not illustrated one by one, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a perspective view showing a conductive grindstone according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing the structure of the segment grindstone in FIG.

FIG. 3 is a view showing the vicinity of the abrasive grains in FIG. 2 in a further enlarged manner.

FIG. 4 is a view showing another embodiment of the present invention and corresponds to FIG.

FIG. 5 is a diagram showing still another embodiment of the present invention, and FIG.
It is a figure corresponding to.

[Explanation of symbols]

 16: Segment grindstone 18: Abrasive grain 20: Binder 24: Nickel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sumito Left Ago Noritake Company Limited No. 1-33 No. 36, Noritake Shinmachi, Nishi-ku, Nagoya City, Aichi Prefecture

Claims (7)

[Claims] 1. A conductive grindstone containing abrasive grains and a vitrified binder binding the abrasive grains, wherein the surface of the vitrified binder contains a metal generated by thermal decomposition. Conductive grindstone. 2. The conductive grindstone according to claim 1, wherein the metal is Ni (nickel). 3. A conductive grindstone containing abrasive grains and a vitrified binder binding the abrasive grains, wherein the vitrified binder contains a rare earth metal hexaboride. Conductive grindstone. 4. The conductive grindstone according to claim 1, wherein the conductive grindstone has open pores, and a nickel plating layer is formed on the inner surface of the open pores. 5. A method for producing a conductive grindstone in which abrasive grains are bonded with a vitrified bond, comprising: a mixing step of mixing a grindstone raw material containing a vitrified bond, a metal boride, and abrasive grains; A forming step of forming the raw material into a grindstone forming body having a predetermined shape, and by firing the grindstone forming body at a predetermined firing temperature, the abrasive grains are bound by the vitrified binder and at least one of the metal borides is formed. And a firing step of thermally decomposing the part to generate a metal element. 6. The method for manufacturing a conductive whetstone according to claim 5, wherein the metal boride is nickel boride. 7. The metal boride is Ni ₃ B. 5.
The method for manufacturing a conductive whetstone.