JP2010184325A - Porous vitrified bond grindstone and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous vitrified bond grindstone excellent in its sharpness and its life and excellent in its continuity of sharpness and its grinding efficiency. <P>SOLUTION: In the porous vitrified bond grindstone 5 having pores 4 in which diamond abrasive grains 1a, 1b and 2 are bonded by a vitrified bond 3, the diamond abrasive grains 1a, 1b and 2 include the diamond abrasive grains 1a arranged in the peripheries of the spaces of the pores 4 and the diamond abrasive grains 2 arranged in the vitrified bond 3. The individual diamond abrasive grains 1a arranged in the peripheries of the spaces of the pores 4 have surfaces in contact with the vitrified bond 3 and surfaces in contact with the spaces of the pores 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diamond grindstone used for grinding a hard and brittle material such as a diamond sintered body, and particularly to one using vitrified bond as a binder for superabrasive grains.

  Conventionally, a vitrified bond grindstone in which superabrasive grains such as diamond abrasive grains and CBN abrasive grains are bonded by vitrified bonds is known as a tool for grinding hard and brittle materials such as diamond sintered bodies. In the vitrified bond diamond grindstone, crushing occurs as grinding is performed, so that the sharpness is not maintained, and uncut portions are generated, resulting in deterioration of grinding efficiency and processing accuracy. For this reason, it is necessary to frequently perform dressing (sharpening) for dropping the clogged diamond and protruding diamond abrasive grains having a cutting edge.

  The vitrified bond diamond wheel has no pores and is inferior in sharpness, but the diamond abrasive grain holding power is strong, the wear of the wheel is low, and the wheel life is long. There is a perforated vitrified bond diamond wheel.

  The conventional porous vitrified bond diamond grindstone has a problem that since the vitrified bond content is reduced by the amount of pores, the holding power of diamond abrasive grains is low and the grindstone life is short. The porous vitrified bond diamond wheel increases the vitrified bond content, which increases the retention of the diamond abrasive and improves the life of the wheel. Will get worse. For this reason, there is a need for a porous pore-bonded diamond diamond wheel that is excellent in both sharpness sustainability and wheel life.

    As what solves this problem, for example, as described in Patent Document 1, by using diamond grains having different crushability and holding power, diamond grains having low holding power and low crushability fall off. A method in which the cutting edge is created and the sharpness is maintained by crushing high crushing diamond abrasive grains that have high holding power and crushing with high holding power and crushing diamond grains. Is disclosed.

  Further, Patent Document 2 discloses a method in which the CBN fine powder or diamond fine powder added in the vitrified bond cuts long chips to shorten the wear of the bond due to the long chips and to improve the life of the grindstone. ing.

  Further, in Patent Document 3, the diamond abrasive grains are heat treated at 850 ° C. in air or 1000 ° C. in vacuum as shown in the examples, thereby improving the bondability with the vitrified bond and increasing the holding power of the diamond abrasive grains. A method of increasing the wheel life by increasing the number is disclosed.

JP-A-11-277439 JP 7-96464 A JP 59-69266

  However, in the method of Patent Document 1, since the grinding becomes impossible when the high holding force and the high crushability of the diamond abrasive grains disappear, there is a limit in the durability of the sharpness, and the time until the next dressing is performed. Represents a short life span.

  In the method of Patent Document 2, since the wear resistance of the bond is increased by adding CBN fine powder or diamond fine powder to the bond, the clogged diamond abrasive grains are difficult to fall off during grinding, and the sharpness is not sustained. .

  Moreover, in the method of patent document 3, since the diamond abrasive grain is heat-processed and only the thing of a high holding power state is used, it will be in the state where the diamond abrasive grain which was crushed is hard to fall off during grinding, and a sharpness is not maintained. . Further, since the heat treatment is performed at 650 ° C. or more, which is thermally damaged by diamond, the diamond abrasive grains are excessively worn.

  This invention is made | formed in view of the said problem, The process which makes it the objective is to provide the porous pore-bonded bond grindstone excellent in the sustainability of a sharpness, the grindstone life, and the grinding efficiency.

  The porous vitrified bond grindstone according to the first aspect of the present invention is a porous vitrified bond grindstone in which superabrasive grains are bonded and held by vitrified bonds in a state including pores. And a second superabrasive grain group, wherein the first and second superabrasive grain groups have different surface properties.

  The second superabrasive grain group may be larger in size than the first superabrasive grain group.

  The first superabrasive grain group and the second superabrasive grain group may be made of the same material.

  Further, both the first superabrasive grain group and the second superabrasive grain group may be made of diamond abrasive grains.

  Moreover, a part of said 1st superabrasive grain group has the superabrasive grain which contacts the said pore, and the surface area of the surface which contacts the said pore of the said superabrasive grain becomes a ratio of 50% or more. It may be.

  The first superabrasive grain group may be 10 to 50% by volume with respect to all superabrasive grains contained therein.

Moreover, the average particle size of the first superabrasive grain group may be 1/20 to 1/1 of the average particle size of the second superabrasive grain. You may make it be 10 to 40% of the volume.

  Further, the porous vitrified bond grindstone according to the second aspect of the present invention is a porous vitrified bond grindstone in which superabrasive grains are bonded and held by vitrified bonds in a state including pores. The first superabrasive grain group having a plurality of abrasive grains arranged at the boundary between the pores and the vitrified bond; and the vitrified bond is higher in wettability than the first superabrasive grain group, and the vitrified And a plurality of second superabrasive grains arranged substantially in a bond.

  The method for producing a porous vitrified bond grindstone according to the third aspect of the present invention comprises molding a mixture containing two or more types of superabrasive grains having the same material and different surface properties, and a vitrified bond. It is manufactured by firing so as to form.

  The superabrasive grain group may include diamond grains that have been heat-treated and diamond grains that have not been heat-treated.

  Moreover, it is preferable that the said heat processing is performed at a temperature range of 300-600 degreeC in air | atmosphere atmosphere.

  According to the invention of claim 1, the superabrasive grains are composed of a first superabrasive grain group and a second superabrasive grain group, and the first and second superabrasive grain groups have surface properties. Since they are configured differently, a part of the abrasive grains in the first superabrasive grain group is fixed in a state where the holding force against the vitrified bond is weak in a state where it is in contact with the boundary between the pores and the vitrified bond. For this reason, during the grinding process, the abrasive grains arranged around the pores are dropped before becoming clogged, so that grinding with new abrasive grains is performed and a sharp state can always be maintained.

  Moreover, since the dropped abrasive grains become free abrasive grains and cause the effect of grinding the work material, and further the vitrified bond is scraped, the wetness with the vitrified bond is high, and the second super-disposed in the vitrified bond. Since the abrasive grains constituting the abrasive grain group are protruded or the diamond abrasive grains arranged inside the vitrified bond are dropped, the sharpness is further maintained.

  Furthermore, since the abrasive grains arranged in the vitrified bond are in a state where the entire surface is covered with the vitrified bond, the abrasive grains are firmly held. Therefore, excessive wheel wear can be prevented and the life of the wheel can be improved.

  According to the invention of claim 2, since the second superabrasive grain group is larger in size than the first superabrasive grain group, it is possible to improve the detachability of the abrasive grains, and the sharpness is further improved. Sustainability can be improved.

  According to the invention of claim 3, the first superabrasive grain group and the second superabrasive grain group are composed of the superabrasive grain group having a plurality of properties from the same material, thereby reducing the manufacturing cost. Can do.

  According to the invention of claim 4, since both the first superabrasive grain group and the second superabrasive grain group are made of diamond abrasive grains, it is possible to manufacture a grindstone having good grinding performance.

  According to invention of Claim 5, a part of 1st superabrasive grain group has a superabrasive grain which contacts the said pore, and the surface area of the surface which contacts the said pore of the said superabrasive grain is 50%. Since it is the above ratio, the 1st superabrasive grain group can be effectively dropped off.

  According to the invention of claim 6, the first superabrasive grain group has a volume ratio of 10 to 50% with respect to the total superabrasive grains contained therein, thereby further improving the effect as a free abrasive grain. be able to.

  According to the invention of claim 7, the average particle size of the first superabrasive grain group is 1/20 to 1/1 of the average particle size of the second superabrasive grain, so that it works as a free abrasive grain. A sufficient effect can be obtained and the work finish of the work material can be enhanced.

  According to the eighth aspect of the present invention, when the pore volume is 10 to 40% of the total volume, the diamond abrasive grains arranged around the pore space can be effectively dropped off.

  According to the invention of claim 9, in the porous vitrified bond grindstone formed by bonding and holding the superabrasive grains with vitrified bonds in a state including pores, the superabrasive grains are at the boundary between the pores and the vitrified bonds. A plurality of first superabrasive grain groups and a second superabrasive grain group having a higher wettability with vitrified bonds than the first superabrasive grain groups, and a plurality of second superabrasive grain groups substantially enclosed in the vitrified bonds. A grinding wheel that improves grinding efficiency by separating superabrasive grains into abrasive grains that separate from the binder and grind between the workpiece and abrasive grains that grind inside the binder. Can be realized.

  According to the invention of claim 10, since it is manufactured by molding a mixture containing two or more types of superabrasive grains having the same material and different surface roughnesses and vitrified bonds, and firing to form pores, Abrasive grains with different wettability with the binder are internally generated, and a plurality of superabrasive grains arranged at the boundary between the pores and the vitrified bond, and a plurality of superabrasive grains arranged inside the vitrified bond. And can be configured.

  According to the invention of claim 11, two or more types of superabrasive grains having different surface properties with the same material include diamond grains by performing heat treatment and diamond grains that have not been heat treated, Diamond abrasive grains can be placed in the vitrified bond and around the pore space.

According to the twelfth aspect of the present invention, the diamond abrasive grains are subjected to heat treatment in the air atmosphere at a temperature range of 300 to 600 ° C., so that the diamond abrasive grains are not thermally damaged. Oxygen is chemically bonded to carbon, which is the constituent element on the outermost surface, and wettability with the vitrified bond can be improved.

1 is an overall view of a porous hole vitrified bond grindstone according to an embodiment of the present invention. The cross-sectional schematic diagram of the porous hole vitrified bond grindstone which concerns on embodiment of this invention. The cross-sectional schematic diagram at the time of grinding of the porous pore vitrified bond grindstone concerning the embodiment of the present invention. The cross-sectional schematic diagram of the conventional porous hole vitrified bond grindstone (comparative example).

  DESCRIPTION OF EMBODIMENTS Hereinafter, a porous hole vitrified bond grindstone according to an embodiment of the present invention will be described with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is an overall view of a porous hole vitrified bond diamond grindstone according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a porous hole vitrified bond diamond grindstone according to an embodiment of the present invention. The perforated vitrified bond diamond grindstone 5 includes a disc-shaped grindstone substrate 7 provided with a tool attachment portion at the center and a grindstone layer 6 fixed to the outer periphery thereof by sintering. The abrasive grain layer 6 is composed of diamond abrasive grains 1 a, 1 b, 2, vitrified bonds 3 that connect the diamond abrasive grains 1 a, 1 b, 2, and pores 4 formed inside the vitrified bond 3. Diamond abrasive grains contained in the porous vitrified bond diamond grindstone 5 are diamond abrasive grains 1a (first superabrasive grain group) arranged around the pores 4 and diamond abrasive grains arranged in the vitrified bond 3. 2 (second superabrasive grain group). The diamond abrasive grains 1a arranged around the pores 4 are arranged such that 50% or more of the surface area of the abrasive grains faces the pores. On the other hand, the diamond abrasive grains 2 arranged in the vitrified bond 3 are almost in contact with the vitrified bond 3 in the entire surface area.

  Next, the effect | action at the time of grinding of the porous hole vitrified bond grindstone 5 by this Embodiment is demonstrated using FIG.

  The perforated vitrified bond grindstone 5 is structured as described above, and the main grinding is performed by the diamond abrasive grains 2 protruding from the contact surface with the work material. The diamond abrasive grains 2 that are almost in contact with the vitrified bond 3 are in a state in which the bonds are good and the diamond abrasive grain holding power is strong, so that the diamond abrasive grains 2 are unlikely to fall off. Therefore, even if the grinding resistance increases to some extent, no drop occurs, and grinding is performed in a form in which the diamond abrasive grains 2 are crushed, so wear of the grindstone can be suppressed.

  At this time, the diamond abrasive grains 1a arranged around the pores 4 are fixed in a state where the diamond abrasive grains have a low holding power and are likely to fall off because the surface area in contact with the vitrified bond 3 is less than 50%. Yes. Accordingly, the diamond abrasive grains 1a that can no longer withstand the grinding resistance fall off and new cutting edges appear, so that the sharpness is excellent.

  Further, the dropped diamond abrasive grains 1a enter between the diamond abrasive grains 2 firmly held by the vitrified bond 3 and the work material, and work as free abrasive grains, so that the grinding efficiency is higher than in the case of only fixed abrasive grains. Will improve. In addition, the diamond abrasive grains 1a that have fallen off as free abrasive grains appropriately conspicuously crush the diamond abrasive grains 2 and the vitrified bond 3, so that a grindstone with excellent sharpness can be obtained.

  In addition, since the porous vitrified bond grindstone 5 according to the present embodiment has pores 4 inside, the diamond abrasive grains 1a in which the pores 4 function as free abrasive grains are captured and again acted as grinding. Therefore, a grindstone with high grinding efficiency can be obtained.

  Due to the above-described effects, a sharpness and a grinding wheel life are excellent, and a grinding stone having excellent sharpness and grinding efficiency can be obtained.

  Next, the manufacturing method of the porous hole vitrified bond grindstone 5 which is this Embodiment is demonstrated.

  The porous vitrified bond grindstone 5 having pores in the present embodiment includes an unheated (non-heat treated) diamond abrasive grain 1, a thermally treated diamond abrasive grain 2, and a vitrified bond 3. It can be manufactured by weighing and mixing, placing in a mold, performing a cold press, and performing firing at a temperature that is equal to or higher than the softening point of the vitrified bond 3 in a state containing air inside.

  The diamond abrasive grains 2 subjected to the heat treatment are preliminarily heat-treated in the air atmosphere in the range of 300 to 600 ° C. before mixing, so that oxygen is chemically bonded to carbon that is a constituent element of the diamond abrasive grain outermost surface, The wettability (so-called bond strength) with the vitrified bond 3 is in a good state. Further, the higher the heating temperature, the better the wettability of the diamond abrasive grains. When the heating temperature is low, the effect of improving the wettability is reduced, so that the wettability can be adjusted by the heating temperature.

  By adjusting the wettability by the heat treatment, the vitrified bond 3 that has been softened and melted in the firing stage preferentially takes in and bonds the heat treated diamond abrasive grains 2 with good wettability. Grain 2 can be arranged. Further, since most of the non-heat-treated diamond abrasive grains 1 are repelled out of the vitrified bond 3, the diamond abrasive grains 1a can be arranged around the pore 4 space. Even in the case of the non-heat-treated diamond abrasive grain 1, when there are many vitrified bonds 3 around the periphery of the diamond abrasive grains 1 and there are few pores 4, the diamond abrasive grains 1 are arranged in the vitrified bond 3 and almost all the surface area is in contact with the vitrified bond 3. Diamond abrasive grains 1b are obtained.

  According to such a configuration, in the porous hole vitrified bond grindstone 5 in which diamond abrasive grains as superabrasive grains are bonded and held by the vitrified bond 3 in a state including the pores 4, the super abrasive grains are wettable. The first superabrasive grain group 1 that is low and disposed around the pores in the vitrified bond and the second superabrasive grain group 1 are arranged in the vitrified bond 3 by improving the wettability by performing heat treatment in advance. The first superabrasive grain group 1 is in contact with the boundary portion between the pores 4 and the vitrified bond 3 by configuring the superabrasive grain group 2 and making the properties of the respective surfaces different. The vitrified bond 3 is fixed in a weak state. Therefore, since the superabrasive grains 1a fall off before the crushing state during grinding, grinding with new abrasive grains can be performed and a sharp state can always be maintained.

  Further, the dropped abrasive grains 1a become free abrasive grains to generate an effect of grinding the work material, and further, the vitrified bond 3 is shaved, so that the second superabrasive grain group 2 is protruded or the vitrified bond 3 is formed. Since the crushed diamond abrasive grains are removed, the sharpness is further maintained.

  Further, since the abrasive grains 2 disposed in the vitrified bond are in a state where the entire surface is covered with the vitrified bond 3, the holding force is strong. Therefore, excessive wear of the grindstone 5 can be prevented and the life of the grindstone can be improved.

  In addition, the second superabrasive grain group 2 is larger in size than the first superabrasive grain group, so that it is possible to improve the detachability of the abrasive grains, and to further improve the sharpness. .

  In addition, since the first superabrasive grain group 1a and the second superabrasive grain group 2 are made of the same material, it is possible to reduce the manufacturing cost.

  Further, since both the first superabrasive grain group 1a and the second superabrasive grain group 2 are made of diamond abrasive grains, it is possible to manufacture the grindstone 5 having good grinding performance.

  The superabrasive grains 1a constituting the first superabrasive grain group have a surface that contacts the pores 4 and a surface that contacts the vitrified bond 3, and the surface area of the surface that contacts the pores 4 is 50% or more. Since it is a ratio, the 1st superabrasive grain group 1a can be effectively dropped off. If it is less than 50%, the holding force of the diamond abrasive grains 1 arranged around the space of the pores 4 becomes large and it is difficult to fall off, which may cause crushing and reduce grinding efficiency. .

  Moreover, the 1st superabrasive grain group 1a can heighten the effect as a free abrasive grain more by being 10 to 50% by volume ratio with respect to all the superabrasive grains contained inside. If it is less than 10%, the number of abrasive grains acting as loose abrasive grains is small, so there is no effect of grinding the work material. Moreover, when it exceeds 50%, since the abrasive grains arrange | positioned in the vitrified bond 3 decrease, the lifetime of the grindstone 5 will fall.

  In addition, since the average particle size of the first superabrasive grain group 1a is 1/20 to 1/1 of the average particle size of the second superabrasive grain 2, the effect of acting as free abrasive grains is sufficiently obtained. In addition, the work finish of the work material can be enhanced. When the average grain size of the diamond abrasive grains arranged around the pore space is less than 1/20 of the average grain diameter of the diamond abrasive grains 2 arranged inside the vitrified bond 3, grinding is performed as free abrasive grains. When the average particle size exceeds 1/1, the load when working as free abrasive grains increases, which causes a problem of increased chipping of the processed surface, which is not preferable.

  Moreover, when the volume of the pores 4 is 10 to 40% of the entire volume, the diamond abrasive grains 1 arranged around the pore 4 space can be effectively dropped off. When the volume ratio of the pore 4 space is less than 10%, the number of diamond abrasive grains 1 around the pore 4 space is insufficient and the effect of free abrasive grains is difficult to obtain. When the volume ratio exceeds 40%, the vitrified bond 3 Since the ratio decreases, the holding power of the diamond abrasive grains 2 arranged in the bridge of the vitrified bond 3 is weakened, and even the diamond abrasive grains having a cutting edge are excessively dropped and the grindstone life is impaired.

  Further, in a porous vitrified bond grindstone 5 in which superabrasive grains are bonded and held by vitrified bonds 3 in a state including pores, a plurality of superabrasive grains are arranged at the boundary portions between the pores 4 and the vitrified bonds 3. In addition, the first superabrasive grain group 1a and the second superabrasive grain group 2 that are higher in wettability with the vitrified bond 3 than the first superabrasive grain group 1a and that are substantially contained in the vitrified bond 3 are arranged. The superabrasive grains are separated into abrasive grains 1 that are separated from the binder and ground with the workpiece, and abrasive grains 2 that are ground inside the binder, thereby reducing the grinding efficiency. An improved grindstone can be realized.

  Moreover, since it is manufactured by molding a mixture containing two or more types of superabrasive grains having the same material and different surface roughnesses and vitrified bond 3 and firing so as to form pores 4, Abrasive grains having different wettability are generated therein, and a plurality of first superabrasive grain groups 1a arranged at the boundary portion between the pores 4 and the vitrified bond 3 and a plurality of first superabrasive grains arranged in the vitrified bond 3 are arranged. 2 superabrasive grain groups 2 can be formed.

  In addition, two or more types of superabrasive grains having different surface roughness with the same material include diamond abrasive grains 2 that have been heat-treated before firing and diamond abrasive grains 1 that have not been heat-treated before firing. Diamond abrasive grains can be placed in the vitrified bond and around the pore space.

  In addition, the heat treatment of the diamond abrasive grain 2 performed before firing is performed at a temperature range of 300 to 600 ° C. in the air atmosphere, so that the diamond abrasive grain 2 is not damaged by thermal damage, and the diamond abrasive grain 2 is thermally damaged. Oxygen is chemically bonded to carbon, which is a constituent element on the surface, and wettability with the vitrified bond 3 can be improved. When the heat treatment temperature is less than 300 ° C., oxygen cannot be chemically bonded to carbon, which is the constituent element of the diamond abrasive grain 2, and when it exceeds 600 ° C., the diamond abrasive grain 2 is thermally damaged. It is not preferable because it will receive.

  As mentioned above, although demonstrated based on embodiment which shows this invention, this invention is not limited to the above-mentioned form, A various change is possible within the range which does not deviate from the meaning. For example, in this embodiment, the grindstone having a segment type abrasive layer has been described, but it may be a ring having an abrasive layer in the entire outer periphery, or it is used by being attached to the shaft end like a drill bit. It may be a form. Moreover, the joining method of an abrasive grain layer and a grindstone board | substrate is not restricted to sintering, For example, the method using an adhesive agent may be used.

  Next, the grinding performance of the porous hole vitrified bond grindstone 5 according to the present embodiment will be described. The above-described porous vitrified bond grindstone 5 according to the present embodiment is used as an example, and as shown in FIG. 4, the porous vitrified bond consisting only of diamond abrasive grains 2 arranged so as to be embedded in the vitrified bond 3. The grindstone 5 was used as a comparative example.

  The porous porous vitrified bond wheel 5 of the examples and comparative examples is a mixture of non-heat-treated diamond abrasive grains 1, heat-treated diamond abrasive grains 2, and vitrified bond 3 according to the composition table shown in Table 1, Firing was performed in a nitrogen atmosphere. Non-heat treated diamond abrasive grains used an average particle diameter of 5 μm, and heat-treated diamond abrasive grains used an average grain diameter of 25 μm. Further, in order to adjust the wettability with the vitrified bond 3, non-heat treated diamond abrasive grains were used, and diamond abrasive grains pre-heated at 500 ° C. were used.

The grinding test of an Example and a comparative example was done on condition of the following.
・ Grinder: Makino CNV2-40 Tool grinder Work material: Composite material of diamond sintered body and carbide material Dimensions: Width 8.0 mm, thickness 3.2 mm (diamond sintered body thickness 0.5 mm, Carbide thickness 2.7mm)
・ Wheel peripheral speed: 12m / s
・ Total depth of cut: 0.05mm
-Depth of cut: 0.001 mm / pass
Table 2 shows the results of the grinding test. As for the porous hole vitrified bond grindstone 5 of the example, the grinding amount is improved by 20% compared with the comparative example, and the grinding ratio (the value obtained by dividing the removal volume of the workpiece obtained by grinding by the grinding wheel wear volume) is 30% Improved grinding efficiency and wheel life. Moreover, although the same test was repeated 3 times, the sharpness decline was not recognized but it was confirmed that the grindstone has a good sharpness sustainability.

DESCRIPTION OF SYMBOLS 1a: Diamond abrasive grain 1b arrange | positioned around pore space 1b: Diamond abrasive grain arrange | positioned in vitrified bond 2: Diamond abrasive grain arrange | positioned in vitrified bond 3: Vitrified bond 4: Pore 5: Air hole Vitrified bond whetstone

Claims (12)

In the porous pore vitrified bond grindstone formed by bonding and holding superabrasive grains with vitrified bond in a state including pores,
The superabrasive grain is composed of a first superabrasive grain group and a second superabrasive grain group, and the first and second superabrasive grain groups have different surface properties. Vitrified bond whetstone.   2. The porous vitrified bond grindstone according to claim 1, wherein the second superabrasive grain group is larger in size than the first superabrasive grain group.   The said 1st superabrasive grain group and the said 2nd superabrasive grain group consist of the same raw material, The porous hole vitrified bond grindstone of Claim 1 or Claim 2 characterized by the above-mentioned.   4. The porous vitrified bond grindstone according to claim 3, wherein each of the first superabrasive grain group and the second superabrasive grain group is composed of diamond abrasive grains.   A part of the first superabrasive grain group has superabrasive grains in contact with the pores, and the surface area of the surface of the superabrasive grains in contact with the pores is a ratio of 50% or more. The porous hole vitrified bond grindstone according to any one of claims 1 to 4.   6. The first superabrasive grain group is 10 to 50% in a volume ratio with respect to all superabrasive grains contained therein, 6. The porous hole vitrified bond grindstone described in 1.   7. The average particle size of the first superabrasive grain group is 1/20 to 1/1 of the average particle size of the second superabrasive grain. 8. The porous pore vitrified bond grindstone according to any one of them.   The porous pore-bonded grindstone according to any one of claims 1 to 7, wherein a volume of the pores is 10 to 40% of a total volume. In the porous pore vitrified bond grindstone formed by bonding and holding superabrasive grains with vitrified bond in a state including pores,
The superabrasive grain is a first superabrasive grain group having a plurality of abrasive grains arranged at the boundary between the pores and the vitrified bond;
A porous vitrified bond comprising: a plurality of second superabrasive grains which are higher in wettability with the vitrified bond than the first superabrasive grains and are substantially included in the vitrified bond. Whetstone.   A porous pore-bonded bond grindstone manufactured by molding a mixture containing two or more types of superabrasive grains having the same material and different surface properties and a vitrified bond, and firing to form pores. Manufacturing method.   The method for producing a porous vitrified bond grindstone according to claim 10, wherein the superabrasive grain group includes a diamond grain that has been heat-treated and a diamond grain that has not been heat-treated.   The method for producing a porous hole vitrified bond grindstone according to claim 11, wherein the heat treatment is performed in an air atmosphere at a temperature range of 300 to 600 ° C.

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