WO2025206380A1 - Superabrasive grain vitrified grindstone having large diameter pores, manufacturing method therefor, and cup-type grindstone wheel - Google Patents

Abstract

Provided is a superabrasive grain vitrified grindstone having large diameter pores with which grindstone preparation adjustment can be performed easily because cracks do not readily form, stable manufacturing is possible, and there is no uneven distribution of pore diameters. This segment grindstone (superabrasive grain vitrified grindstone having large diameter pores) 14 includes hollow granulated bodies 20 having outer shells 26 to which diamond abrasive grains (superabrasive grains) 18 are bonded by a vitrified bond, wherein the inner cavities of the hollow granulated bodies 20 form large diameter pores 22 in a multi-pore structure of the segment grindstone 14. As a result, the hollow granulated bodies 20 are uniformly mixed with little unevenness in a kneading material to be used for molding, and thus a segment grindstone 14 is obtained in which grindstone preparation adjustment can be performed easily because cracks do not readily form, stable manufacturing is possible, and there is no uneven distribution of pore diameters.

Description

Superabrasive vitrified grinding wheel with large pores, its manufacturing method, and cup-type grinding wheel

The present invention relates to a superabrasive vitrified grinding wheel with large pores, in which superabrasive grains are bonded using a vitrified bond, a method for manufacturing the same, and a cup-shaped grinding wheel.

Generally, when surface grinding semiconductors such as SiC, superabrasive grains such as diamond are bonded using a vitrified bond to increase grain retention and favorably generate self-sharpening cutting edges. This type of superabrasive grain vitrified grinding wheel is proposed, with many large pores included. Because such superabrasive grain vitrified grinding wheels ensure sufficient grinding strength, they can be used for grinding with sufficient grinding pressure, resulting in good grinding performance. Examples of such superabrasive grain vitrified grinding wheels are those described in Patent Documents 1, 2, 3, and 4.

The superabrasive vitrified grinding wheels described in Patent Documents 1 and 2 use a resin pore-forming material to create large pores, and the large pores are formed by eliminating the resin pore-forming material during the firing process. However, the resin pore-forming material has a smooth surface and a large difference in density from the abrasive grains and vitrified bond, which means that even when kneaded, the resin pore-forming material tends to become uneven, causing large pores to be distributed ubiquitously and making the wheels prone to cracking.

The superabrasive vitrified grinding wheel described in Patent Document 3 is manufactured by mixing superabrasive grains, vitrified bond, gelling agent, water, and surfactant to obtain a meringue-like foam material, then cooling the foam material in a molding die to create a molded body, which is then dried and baked, and then immersed in liquid resin to coat the bond bridge, which is the outer shell surrounding the pores, with a resin coating layer to increase its strength. However, when manufacturing superabrasive vitrified grinding wheels using this manufacturing method, the molded body shrinks, making it difficult to produce products with a stable shape.

The superabrasive vitrified grinding wheel described in Patent Document 4 is obtained by placing a molded body with frozen particles formed inside it under vacuum, causing the frozen particles inside the molded body to sublimate, forming large pores in the areas after sublimation, and then firing the molded body. However, there are drawbacks in that it is difficult to adjust the grinding wheel's formulation, and the pore size is likely to differ between the surface and interior of the grinding wheel.

Patent No. 5414706 JP 2017-1185575 A Patent No. 4769488 Patent No. 6737975

The present invention was made against the backdrop of the above circumstances, and its purpose is to provide a superabrasive vitrified grinding wheel that is less susceptible to cracking, can be manufactured stably, and has large pores with no bias in pore size, allowing for easy wheel blend adjustment.

As a result of extensive research conducted against the background of the above circumstances, the inventors discovered that densely packed hollow granules can be reliably obtained by spraying a slurry containing superabrasive grains, vitrified bond, binder, etc. in a spray dryer and drying it in air. They then discovered that by press-molding the classified hollow granules and sintering them, a superabrasive vitrified grinding wheel with large pores that is less likely to crack, can be manufactured stably, and has no bias in pore size, allowing for easy wheel blend adjustment. The present invention was made based on these findings.

In other words, the gist of the first invention is (a) a superabrasive vitrified grinding wheel in which superabrasive grains are bonded together with a vitrified bond and have large-diameter pores within a porous structure, and (b) the superabrasive grains include hollow granules having an outer shell bonded together with the vitrified bond, and the inner cavity of the hollow granules forms the large-diameter pores.

The gist of the second invention is that, in the first invention, the ratio of the shell thickness to the outer diameter of the hollow granule is 0.1 to 0.4.

The gist of the third invention is that, in the first invention, the porous structure contains pores with an average pore diameter of 5 to 60 μm.

The gist of the fourth invention is that, in the first or second invention, the superabrasive grains are 10 μm diameter or less, and the hollow granules have an outer shell with a thickness of 5 to 10 μm and an outer diameter of 10 to 100 μm.

The gist of the fifth invention is that the superabrasive vitrified grinding wheel with large pores of the first invention is a cup-shaped grinding wheel in which the large pore-containing superabrasive vitrified grinding wheel is fixed to the outer periphery of a metal base metal in a series at predetermined radial intervals.

The gist of the sixth invention is a method for manufacturing a superabrasive vitrified grinding wheel in which superabrasive grains are bonded together with a vitrified bond and the superabrasive grains have large pores within their porous structure, and the method includes: a slurry preparation step for preparing a slurry containing the superabrasive grains, the vitrified bond, and a binder; a spray-dry granulation step for spraying the slurry in a dryer and drying it in air to obtain hollow granules from the slurry droplets; a molding step for press-molding the hollow granules obtained in the spray-dry granulation step in a mold to obtain a green body; and a firing step for firing the green body to obtain a superabrasive vitrified grinding wheel in which the superabrasive grains are bonded together with the vitrified bond and the superabrasive grains have large pores within their porous structure.

In the superabrasive vitrified grinding wheel with large pores of the first invention, the superabrasive grains contain hollow granules with an outer shell bound by a vitrified bond, and the inner cavities of these hollow granules form the large pores within the porous structure of the superabrasive vitrified grinding wheel. As a result, the hollow granules are uniformly mixed in the mixed material with little uneven distribution, resulting in a superabrasive vitrified grinding wheel with large pores that is less likely to crack, can be manufactured stably, and has no bias in pore size, allowing for easy wheel blend adjustment.

In the superabrasive vitrified grinding wheel with large pores of the second invention, the ratio of the shell thickness to the outer diameter of the hollow granules is 0.1 to 0.4. This ensures that the hollow structure of the hollow granules is maintained appropriately during press molding. If the ratio of the shell thickness to the outer diameter of the hollow granules is less than 0.1, the strength of the hollow granules decreases and the hollow structure is destroyed. If the ratio of the shell thickness to the outer diameter of the hollow granules exceeds 0.4, the hollow structure deforms during the spray drying process, resulting in the formation of defective granules with no internal cavity, making it difficult to obtain a superabrasive vitrified grinding wheel with large pores within its porous structure.

In the superabrasive vitrified grinding wheel with large pores of the third invention, the porous structure contains pores with an average pore diameter of 5 to 60 μm. This results in a superabrasive vitrified grinding wheel with large pores that has high grinding performance.

In the superabrasive vitrified grinding wheel with large pores of the fourth invention, the superabrasive grains are 10 μm diameter or less, and the hollow granules have an outer shell 5 to 10 μm thick and an outer diameter of 10 to 100 μm. This results in a superabrasive vitrified grinding wheel with large pores that is less prone to cracking, can be manufactured stably, has no bias in pore diameter, and can be easily adjusted for grinding wheel blending.

In the cup-shaped grinding wheel of the fifth invention, the superabrasive vitrified grinding wheels with large pores of the first invention are fixed in a row at predetermined intervals in the radial direction to the outer periphery of the metal base, allowing for the effective use of expensive superabrasive grains.

The sixth invention of the method for producing a superabrasive vitrified grinding wheel with large pores includes a slurry preparation process in which a slurry containing superabrasive grains, a vitrified bond, and a binder is prepared; a spray-drying granulation process in which the slurry is sprayed in a dryer and dried in air to produce hollow granules from the slurry droplets; a molding process in which the hollow granules are press-molded in a mold to produce a green body; and a firing process in which the green body is fired to produce a superabrasive vitrified grinding wheel with large pores within a porous structure in which the superabrasive grains are bonded by the vitrified bond. The spray-drying granulation process allows for the preferable production of hollow granules from the slurry droplets by spraying a slurry containing superabrasive grains, a vitrified bond, and a binder in a dryer and drying it in air. Hollow granules produced in this manner have a relatively uniform particle size and a sharp particle size distribution, resulting in less variation and bias in the pores within the grinding wheel and less cracking.

FIG. 1 is a perspective view showing a cup-shaped grinding wheel equipped with a superabrasive vitrified grinding stone having large-diameter pores according to an embodiment of the present invention. 2 is an optical microscope photograph showing an enlarged view of the surface of the superabrasive vitrified grinding wheel having large pores shown in FIG. 1. 3 is an SEM photograph showing an enlarged view of hollow granules contained in a vitrified bond in the superabrasive vitrified grinding wheel of FIG. 2. FIG. 2 is a diagram illustrating a method for measuring the shell thickness and outer diameter of hollow granules. 2 is a process diagram illustrating a manufacturing process of the superabrasive vitrified grinding wheel having large pores shown in FIG. 1. FIG. 6 is a diagram illustrating the mechanism of formation of hollow granules in the spray-drying granulation process of FIG. 5. FIG. 1 is a process diagram illustrating a method for manufacturing a superabrasive vitrified grinding wheel that does not use hollow granules. 1 is a table showing mixing amounts and grinding test results in grinding test 1. 10 is a table showing mixing amounts and grinding test results in grinding test 2.

Below, one embodiment of the present invention will be described in detail with reference to the drawings. Note that in the following embodiment, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Figure 1 is a perspective view showing a cup-shaped grinding wheel 10 according to one embodiment of the present invention. The cup-shaped grinding wheel 10 comprises a disk-shaped base metal 12 made of metal, for example, aluminum, and a plurality of segment grinding stones 14 fixedly attached at predetermined intervals in a ring-like arrangement along the outer periphery of the underside of the base metal 12. Each segment grinding stone 14 has a grinding surface 16 that is continuous in a ring-like arrangement along the outer periphery of the underside of the base metal 12.

The base metal 12 is a disk made of metal, and is attached to the main shaft of a grinding device (not shown), which rotates the cup-shaped grinding wheel 10. The cup-shaped grinding wheel 10 has an outer diameter of, for example, about 250 mm, and the segment grinding wheel 14 is an arc-shaped plate with a thickness of, for example, about 3 mm. As the base metal 12 rotates, the grinding surface 16 of the segment grinding wheel 14 slides against the workpiece, such as a semiconductor wafer such as SiC, grinding or polishing the workpiece into a flat surface.

The segmented grinding wheel 14 corresponds to the superabrasive vitrified grinding wheel having large-diameter pores 22 of the present invention. As shown in the 200x optical microscope photograph in Figure 2, the segmented grinding wheel 14 is composed of a porous structure including superabrasive grains, such as diamond abrasive grains 18, hollow granules 20, a vitrified bond that bonds the diamond abrasive grains 18 and hollow granules 20, and pores 24 containing the large-diameter pores 22. The inner cavities of the hollow granules 20 form the large-diameter pores 22. The composition of the segmented grinding wheel 14 is, for example, 19-26 vol% diamond abrasive grains 18, 9-12 vol% vitrified bond, and 60-72 vol% pores 24.

The average pore diameter of all pores 24, including the large pores 22 in the porous structure that makes up the segment grinding wheel 14, is, for example, 5 to 60 μm, and preferably 8 to 51 μm, as the average value when the maximum diameter of the pores 24 is measured at 30 or more consecutive points using image measurement under a microscope.

The particle size of the diamond abrasive grains 18 can be selected depending on the required surface roughness, but is, for example, 10 μm or less, preferably an average particle size of 0.6 μm. The vitrified bond is made of well-known borosilicate glass or borosilicate zinc glass. The glass composition is, for example, 10 to 60 wt% SiO ₂ , 10 to 30 wt% B ₂ O ₃ , 0 to 65 wt% ZnO, 0 to 10 wt% RO, and 0 to 10 wt% R ₂ O.

As shown in the 1000x SEM (scanning electron microscope) photograph in Figure 3, the hollow granules 20 are composed of diamond abrasive grains 18, a vitrified bond that bonds the diamond abrasive grains 18, a spherical outer shell 26 made up of a porous structure including pores 24, and large pores 22 that are internal cavities surrounded by the outer shell 26. It is preferable that the hollow granules 20 have an outer diameter D of 10 to 100 μm. If the outer diameter D is less than 10 μm, there will be more solid granules, and if it exceeds 100 μm, defects such as depressions will be more likely to occur.

The outer diameter D of the hollow granules 20 and the thickness T of the outer shell 26 are measured as shown in Figure 4. First, the segment grinding wheel 14 is ground using a fixed abrasive polishing pad to expose the internal surface, and the exposed surface is observed using an optical microscope or SEM. Next, the hollow granules 20 are extracted from the observed image, and their outer diameter D and thickness T of the outer shell 26 are measured using the image. These measurements are then taken for 30 hollow granules 20 in the image, and the average values are calculated.

The thickness T of the outer shell 26 of the hollow granules 20 is, for example, 5 to 10 μm, preferably 8.2 to 9.6 μm, the outer diameter D of the hollow granules 20 is, for example, 10 to 100 μm, preferably 22 to 82 μm, and the ratio T/D of the thickness T of the outer shell 26 of the hollow granules 20 to the outer diameter D of the hollow granules 20 is, for example, 0.1 to 0.4, preferably 0.1 to 0.37.

FIG. 5 is a process diagram illustrating the main steps of the manufacturing process for the segment grinding wheel 14. In the slurry preparation step P1 in FIG. 5, a slurry, which is the material for granulating the hollow granules 20, is prepared. That is, the slurry is prepared by uniformly mixing diamond abrasive grains 18, vitrified bond, PVA, acrylic resin, and a binder such as wax in a predetermined ratio. The binder is a molding aid, and its addition ratio is experimentally adjusted in advance so that the press molding pressure in the molding step P3 described below is 100 to 400 kgf/ ^cm² . This is because if the molding pressure is less than 100 kgf/ ^cm² , the adhesion between the hollow granules 20 will be weak, and if the molding pressure exceeds 400 kgf/ ^cm² , the hollow granules 20 will deform or break.

In the spray-drying granulation process P2, the slurry is sprayed inside the drying furnace of the spray dryer, causing the droplets of the slurry to dry in the air and form hollow granules 20. As shown in Figure 6, during the drying process, the diamond abrasive grains 18 and vitrified bond particles of the droplet-like slurry move outward, while the inner cavity expands and the outer diameter D contracts, forming an outer shell 26, resulting in the formation of hollow granules 20, such as those shown in Figure 3. The hollow granules 20 are classified as necessary. The method for spraying the slurry is selected from a two-fluid nozzle method, a high-pressure nozzle method, a rotating disk method, etc.

Next, in the molding step P3, the hollow granules 20 obtained in the spray-drying granulation step P2 are filled into a press die and pressed at a molding pressure of, for example, 100 to 400 kgf/cm ² .

In the firing process P4, the compact formed in the molding process P3 is fired at a temperature at which the vitrified bond melts, such as 800°C, to obtain the segmented grinding wheels 14. Then, in the bonding and finishing process P5, multiple segmented grinding wheels 14 are bonded to the base metal 12 and finished using a dresser to obtain the cup-shaped grinding wheel 10 shown in Figure 1.

(Grinding test explanation)
Next, the details of grinding tests 1 and 2 conducted by the present inventors using the grinding (polishing) conditions shown below and the results of these grinding tests 1 and 2 will be described below.

In grinding test 1, comparative example 1 and example examples 1 to 4 shown in the table in Figure 8 were used. Example examples 1 to 4 are superabrasive vitrified grinding wheels manufactured with the composition shown in Figure 8, and have large-diameter pores 22 due to the inclusion of hollow granules 20, and have different compositions as shown in Figure 8. Comparative example 1 is a superabrasive vitrified grinding wheel that does not contain hollow granules 20, manufactured using the composition shown in Figure 8 and the manufacturing process shown in Figure 7. In the manufacturing process shown in Figure 7, in the slurry preparation process P11, diamond abrasive grains 18, vitrified bond, and binders such as PVA, acrylic resin, and wax are uniformly mixed in a predetermined ratio to prepare a slurry. Next, in the drying and stirring process P12, the slurry is dried and stirred using an electric mortar and pestle device, and granulated by sieving. In the molding process P13, firing process P14, and bonding/finishing process P15, molding, firing, bonding, and finishing are carried out in the same manner as in the molding process P3, firing process P4, and bonding/finishing process P5 in Figure 5.

In grinding test 2, comparative example 2 and example examples 5-6 shown in the diagram in Figure 9 were used. Example examples 5-6 are superabrasive vitrified grinding wheels with large pores 22 due to the inclusion of hollow granules 20, manufactured using the composition shown in Figure 9 and the process shown in Figure 5, and have different compositions as shown in Figure 9. Comparative example 2 is a superabrasive vitrified grinding wheel without hollow granules 20, manufactured using the composition shown in Figure 9 and the manufacturing process shown in Figure 7.

(Grinding conditions for grinding test 1)
Grinding machine: vertical surface grinding machine Workpiece: C-face grinding wheel for 4-inch SiC wafers Rotation speed: 2400 rpm
Table rotation speed: 150 rpm
Grinding wheel spindle feed speed: 0.4 μm/sec
Wafer removal allowance: 8 μm
Grinding fluid: Water

(Grinding conditions for grinding test 2)
Grinding machine: vertical surface grinding machine Workpiece: C-face grinding wheel for 6-inch SiC wafers Rotation speed: 2500 rpm
Table rotation speed: 311 rpm
Grinding wheel spindle feed speed: 0.6 μm/sec
Wafer removal allowance: 20 μm
Grinding fluid: Water

In Grinding Test 1, as shown in Figure 8, Examples 1 to 4 did not show a significant difference in current value (A) compared to Comparative Example 1, but the amount of wear (μm) was clearly less, resulting in high grinding wheel performance, i.e., high grinding efficiency. This is presumably because the presence of large-diameter pores 22 formed by the hollow granules 20 increases abrasive grain retention and suppresses clogging, thereby favorably achieving the self-sharpening action of the abrasive grains. Examples 1 to 4 have different shapes of the hollow granules 20 contained within the superabrasive vitrified grinding wheel.

As shown in Figure 8, the compositions containing hollow granules 20 in Examples 1 to 4 have smaller abrasive grain volume fractions and vitrified bond volume fractions, and larger average pore diameters, compared to Comparative Example 1. Examples 1 to 4 have abrasive grain volume fractions of 19.3 to 24.4 vol%, vitrified bond volume fractions of 9.6 to 12.0 vol%, average pore diameters of 8 to 45 μm, and hollow granule 20 outer diameters D of 22 to 82 μm. Furthermore, the ratio T/D of the thickness T of the outer shell 26 of the hollow granules 20 contained in Examples 1 to 4 to the outer diameter D is 0.1 to 0.37.

Among Examples 1 to 4, Example 1 has a ratio T/D of the thickness T of the outer shell 26 of the hollow granules 20 to the outer diameter D of the hollow granules 20 of 0.37, which means that the amount of wear is 2.3 times greater than that of Examples 2 to 4. Compared to Examples 2 to 4, Example 1 has a smaller average pore diameter and a larger T/D ratio, which is thought to be due to the lack of a sufficiently large pore structure.

In Grinding Test 2, as shown in Figure 9, there was no significant difference in current value (A) between Examples 5 and 6 and Comparative Example 2, just as in Grinding Test 1. However, the amount of wear (μm) was significantly less, resulting in high grinding wheel performance, i.e., high grinding efficiency. This is also presumably due to the presence of large-diameter pores 22 formed by the hollow granules 20, which provide high abrasive grain retention and suppress clogging, thereby enabling the abrasive grains to effectively self-sharpen their cutting edges.

As shown in Figure 9, for the compositions containing hollow granules 20 in Examples 5 and 6, there is not much difference in the abrasive grain volume ratio and vitrified bond volume ratio compared to Comparative Example 2, but the average pore diameter is larger. The abrasive grain volume ratio of Examples 5 and 6 is larger than that of Examples 1 to 4, but there is not much difference in the vitrified bond volume ratio and average pore diameter. The ratio T/D, which is the thickness T of the outer shell 26 of the hollow granules 20 to the outer diameter D, is within the range of Examples 1 to 4.

In Examples 1 to 6, the abrasive grain volume fraction was 19.3 to 25.9 vol%, the vitrified bond volume fraction was 9.3 to 12.0 vol%, the average pore diameter was 8 to 51 μm, and the outer diameter D of the hollow granules 20 was 22 to 82 μm.

As described above, the segmented grinding wheel (superabrasive vitrified grinding wheel with large pores) 14 of this embodiment includes hollow granules 20 with an outer shell 26 in which diamond abrasive grains (superabrasive grains) 18 are bonded with a vitrified bond, and the inner cavity of these hollow granules 20 forms large pores 22 within the porous structure of the segmented grinding wheel 14. As a result, the hollow granules 20 are uniformly mixed in the mixed material with little uneven distribution, resulting in a segmented grinding wheel 14 that is less likely to crack, can be manufactured stably, and has no bias in pore size, allowing for easy grinding wheel blend adjustment.

Furthermore, with the segmented grinding wheel 14 of this embodiment, the hollow granules 20 have a ratio (=T/D) of the thickness T of the outer shell 26 to the outer diameter D of the hollow granules 20 of 0.1 to 0.4, preferably 0.1 to 0.37. This ensures that the hollow structure of the hollow granules 20 is maintained appropriately during press molding. If the ratio (=T/D) of the thickness T of the outer shell 26 to the outer diameter D of the hollow granules 20 is less than 0.1, the strength of the hollow granules 20 will decrease and the hollow structure will be destroyed. If the ratio (=T/D) of the thickness T of the outer shell 26 to the outer diameter D of the hollow granules 20 exceeds 0.37, the hollow structure will deform during the spray drying process, resulting in the formation of defective granules with no internal cavity, making it difficult to obtain a segmented grinding wheel 14 within a porous structure.

Furthermore, according to the segment grinding wheel 14 of this embodiment, the porous structure contains pores 24 with an average pore diameter of 5 to 60 μm, preferably 8 to 51 μm. This results in a segment grinding wheel 14 with high grinding performance.

Furthermore, in the segmented grinding wheel 14 of this embodiment, the diamond abrasive grains 18 are 10 μm diameter or less, and the hollow granules 20 have an outer shell 26 with a thickness T of 5 to 10 μm, preferably 8.2 to 9.6 μm, and an outer diameter D of 10 to 100 μm, preferably 22 to 82 μm. This results in a segmented grinding wheel (super abrasive vitrified grinding wheel) 14 that is less prone to cracking, can be manufactured stably, and has large-diameter pores with no bias in pore diameter, allowing for easy grinding wheel blend adjustment.

In addition, in this embodiment, the cup-shaped grinding wheel 10 is constructed by fastening the segment grinding stones 14 to the outer periphery of the metal base metal 12 in a row at predetermined intervals in the radial direction. This allows the expensive diamond abrasive grains 18 to be used effectively.

Furthermore, the manufacturing method for the segmented grinding wheel 14 of this embodiment includes a slurry preparation process P1 in which a slurry containing diamond abrasive grains 18, a vitrified bond, and a binder is prepared; a spray-dry granulation process P2 in which the slurry is sprayed in a dryer and dried in air to obtain hollow granules 20 from the slurry droplets; a molding process P3 in which the hollow granules 20 are press-molded in a mold to obtain a green body; and a firing process P4 in which the green body is fired to obtain the segmented grinding wheel 14 in a porous structure in which the diamond abrasive grains 18 are bonded by the vitrified bond. In the spray-dry granulation process P2, a slurry containing diamond abrasive grains 18, a vitrified bond, and a binder is sprayed in a dryer and dried in air, thereby enabling the hollow granules 20 to be suitably obtained from the slurry droplets. The hollow granules 20 granulated in this manner have a relatively uniform particle size and a sharp particle size distribution, which reduces the variation and bias of the pores 24 within the segment grinding wheel 14 and makes cracks less likely to occur.

The above describes in detail one embodiment of the present invention with reference to the drawings, but the present invention is not limited to this embodiment and may be implemented in other forms.

For example, in the above-described embodiment, diamond abrasive grains 18 were used, but other superabrasive grains, such as CBN abrasive grains, may also be used.

Furthermore, in the above-described embodiment, a cup-shaped grinding wheel 10 was used in which multiple segment grinding stones 14 formed into thick, arc-shaped plates were fixed to the outer periphery of the base metal 12, but the segment grinding stones 14 may also be grinding stones of other shapes. For example, they may be cup-shaped or disc-shaped vitrified grinding wheels having a predetermined thickness.

Alternatively, the segment grinding wheel 14 may have a two-layer structure in which the surface layer is made of a super-abrasive vitrified grinding wheel containing diamond abrasive grains 18, and the lower layer is made of aggregate (general abrasive grains or inorganic powder) bonded with a vitrified bond.

Note that the above is merely one embodiment, and although other examples will not be provided, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art, as long as they do not deviate from the spirit of the invention.

10: Cup-shaped grinding wheel 12: Base metal 14: Segment grinding wheel (super abrasive vitrified grinding wheel with large pores)
18: Diamond abrasive grains (super abrasive grains)
20: Hollow granule 22: Large diameter pore 24: Pore 26: Outer shell T: Thickness (thickness of outer shell)
D: Outer diameter (outer diameter of hollow granules)

Claims (6)

A superabrasive vitrified grinding wheel having large pores in a porous structure in which superabrasive grains are bonded by a vitrified bond,
the superabrasive grains include hollow granules having an outer shell bound by the vitrified bond,
The large-diameter pores are formed in the inner cavities of the hollow granules. 2. The superabrasive vitrified grinding wheel having large pores, according to claim 1, wherein the ratio of the thickness of the outer shell to the outer diameter of the hollow granules is 0.1 to 0.4. 2. The superabrasive vitrified grinding wheel having large pores according to claim 1, wherein the porous structure contains pores having an average pore diameter of 5 to 60 μm. The superabrasive grains have a diameter of 10 μm or less,
3. The vitrified superabrasive grinding wheel having large pores, characterized in that the hollow granules have a shell thickness of 5 to 10 μm and an outer diameter of 10 to 100 μm. 10. A cup-type grinding wheel, comprising: a superabrasive vitrified grinding wheel having large pores according to claim 1, fixed to the outer periphery of a metal base metal in a row at predetermined intervals in the radial direction. A method for manufacturing a superabrasive vitrified grinding wheel having large pores in a porous structure in which superabrasive grains are bonded by a vitrified bond, comprising:
a slurry preparation step of preparing a slurry containing the superabrasive grains, the vitrified bond, and a binder;
a spray-drying granulation step in which the slurry is sprayed in a dryer and dried in air to obtain hollow granules from droplets of the slurry;
a molding step of press-molding the hollow granules obtained in the spray-drying granulation step in a mold to obtain a molded body;
and a firing step of firing the compact to obtain a superabrasive vitrified grinding wheel having the large-diameter pores within the porous structure in which the superabrasive grains are bonded by the vitrified bond.