Vitrified bond superabrasive wheel

Abstract

The vitrified bond superabrasive wheel comprises superabrasive grains, fillers, and a vitrified bond, and includes a superabrasive grain layer in which pores are formed. The proportion of fillers with a peripheral length envelope degree of less than 0.90 is between 10% and 40%.

Description

Technical Field

[0001] The present disclosure relates to a vitrified bond superabrasive wheel. This application claims priority based on Japanese Patent Application No. 2024-133794, filed on August 9, 2024. All the descriptions contained in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] Conventionally, vitrified bond superabrasive wheels are disclosed, for example, in Japanese Patent Application Laid-Open No. 2014-61585 (Patent Document 1) and Japanese Patent Application Laid-Open No. 3-228578 (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The vitrified bond superabrasive wheel of the present disclosure includes superabrasives, fillers, and a vitrified bond, and includes a superabrasive layer in which pores are formed. The ratio of the number of fillers with a peripheral length envelope less than 0.90 is 10% or more and 40% or less.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a schematic view showing a crack 7 in a vitrified bond 2 having a single filler 4 with a peripheral length envelope of 1. [Figure 2] FIG. 2 is a schematic view showing a crack 7 in a vitrified bond 2 having a filler 4 with a peripheral length envelope smaller than 1. [Figure 3]Figure 3 is a schematic diagram of one filler shown to illustrate the perimeter envelope of filler 4. [Figure 4] Figure 4 is a schematic diagram of the superabrasive layer 6 of sample number 3. [Figure 5] Figure 5 is a schematic diagram of the superabrasive layer 6 of sample number 1. [Figure 6] Figure 6 is a graph showing the relationship between the periphery length envelope of filler 4 in sample number 3 shown in Figure 4 and the number of fillers, and the relationship between the periphery length envelope of filler 4 in sample number 1 shown in Figure 5 and the number of fillers. [Figure 7] Figure 7 is a photograph of the connected filler 4, which has not been crushed. [Figure 8] Figure 8 shows a superabrasive wheel 20 having a superabrasive layer 6 used for processing SiC wafers. [Figure 9] Figure 9 is a cross-sectional view of the superabrasive wheel 20 along the line IX-IX indicated by arrow IX in Figure 8. [Figure 10] Figure 10 is a schematic diagram of the superabrasive wheel 20 and table 110 shown to illustrate the grinding method using the superabrasive wheel 20. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] There was a need for a vitrified bond superabrasive wheel that offered both excellent cutting performance and high wear resistance. [Effects of this disclosure] According to this disclosure, it is possible to provide a vitrified bond superabrasive wheel that has good cutting performance and is resistant to wear.

[0007] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0008] In the vitrified bond superabrasive wheel described in Patent Document 1, α-Al2O3 (alumina) is added to the superabrasive grains (usually diamond) with an average particle size of 1 μm or less in order to process wafers with high precision.

[0009] Patent Document 2 discloses a vitrified bond superabrasive wheel in which the filler (aggregate) is not limited to alumina, and the hardness can be a wider range of ceramics in general (silicon carbide, zircon, hBN, etc.).

[0010] In conventional techniques, excessive alumina addition leads to a deterioration of cutting performance and increased tool wear when machining difficult-to-cut materials. Alumina is essential for maintaining the framework of the superabrasive layer and enabling the superabrasive grains to penetrate the workpiece. However, when machining hard materials such as silicon carbide (SiC) and sapphire, the alumina added to the wheel cannot penetrate the material. This worsens the cutting performance (grinding resistance), and as a result, wear also increases.

[0011] Reducing alumina to improve cutting performance can lead to increased wear. In other words, one might consider reducing the amount of alumina and increasing the amount of superabrasive grains (diamonds) that form the cutting edge to improve cutting performance. However, doing so impairs the function of alumina as an aggregate. As a result, the grinding wheel breaks easily during processing, and the amount of wear increases. This is because, in vitrified bond superabrasive wheels, the amount of solid material (vitrified bond, superabrasive grains, and filler) cannot be changed independently, and the amount of superabrasive grains reduced must be compensated for by the alumina filler.

[0012] In this disclosure, the vitrified bond superabrasive wheel comprises superabrasive grains, fillers, and a vitrified bond, and has pores. The proportion of fillers with a peripheral envelopment degree (also simply called "envelopment degree") of less than 0.90 is 10% or more and 40% or less.

[0013] In a vitrified bond superabrasive wheel constructed in this manner, the proportion of fillers with a perimeter length envelopment degree of less than 0.90 is between 10% and 40%, resulting in a longer perimeter length and suppressing the occurrence of cracks in the vitrified bond.

[0014] FIG. 1 is a schematic view showing a crack 7 in a vitrified bond 2 having a single filler 4 with a perimeter envelope degree of 1. FIG. 2 is a schematic view showing a crack 7 in a vitrified bond 2 having a filler 4 with a perimeter envelope degree smaller than 1. FIG. 3 is a schematic view of one filler shown to explain the perimeter envelope degree of the filler 4.

[0015] As shown in FIG. 1, in the superabrasive grain layer 6, the filler 4 is held by the vitrified bond 2. The filler 4 of alumina constituting the vitrified bond 2 is nearly circular in shape and is a so-called single grain. The bonding strength between the filler 4 and the vitrified bond 2 is related to the contact area between the filler 4 and the vitrified bond 2.

[0016] Since the filler 4 shown in FIG. 2 has a shape in which a plurality of fillers 4 shown in FIG. 1 are connected, the surface area per grain of the filler 4 becomes larger in FIG. 2. As a result, the strength of holding the filler 4 by the vitrified bond 2 becomes higher.

[0017] Furthermore, in FIG. 1, since there are many gaps between the plurality of fillers 4, the crack 7 can propagate from various paths. On the other hand, in FIG. 2, since the filler 4 has a complex shape, the shape between the fillers 4 is also complex. As a result, the crack 7 is difficult to propagate. And the vitrified bond 2 and the superabrasive grain layer 6 are difficult to be broken.

[0018] FIG. 3 is a schematic view of one filler shown to explain the perimeter envelope degree of the filler 4. The perimeter envelope degree is shown in FIG. 3. The perimeter envelope degree can be calculated by the following formula.

[0019] Perimeter envelope degree = Envelope perimeter length / Actual perimeter length [[ID=!]] If a rubber band is wound around the perimeter of the particle contour, the length of the rubber band in the stretched state is called the "envelope perimeter length". The actual perimeter length refers to the sum of the lengths of the contour lines of the filler 4 particles. As described above, the convex hull of the contour of the filler 4 particles is used as the envelope line, and the perimeter envelope degree is obtained by dividing the length of the envelope line by the length of the contour.

[0020] If there are no irregularities on the surface of the particles, the perimeter-length enveloping degree is 1. When the filler 4 according to this disclosure is applied, a high skeletal structure maintenance effect can be obtained even with a small amount of filler 4. As a result, the amount of abrasive grains that form the cutting edge can be increased without impairing the skeletal structure maintenance function of the grinding wheel. This makes it possible to properly cut into the workpiece with the cutting edge.

[0021] In filler 4, which has an uneven surface due to the interconnected shape of individual grains, there are many particles with a small degree of envelopment over the surrounding area. This reduces the interface between filler 4 and glass, preventing the filler 4 from falling off starting from that interface, and allowing the strength of the grinding wheel to be maintained with a small amount of filler 4.

[0022] Filler 4 may be, for example, particles of ceramic material (mainly oxides or carbides). Filler 4 can be, for example, titanium oxide (TiO2), zirconium oxide (ZrO2), cubic boron nitride (CBN), alumina (Al2O3), silicon dioxide (SiO2), and silicon carbide (SiC). Filler 4 is preferably at least one of alumina (Al2O3), silicon dioxide (SiO2), and silicon carbide (SiC). Alumina, silicon dioxide, and silicon carbide have good wettability with glass and are highly effective in suppressing filler detachment at the interface with glass. Alumina (especially α-alumina) is particularly preferred due to its good wettability with glass.

[0023] A method for manufacturing a filler 4 having such a peripheral length envelope is described below. To combine multiple fillers 4, for example, by crushing, mixing, and heat-treating the fillers 4, a filler 4 having a predetermined peripheral length envelope can be manufactured. This manufacturing method is merely one example. The time for crushing the filler 4, the time for mixing, and the temperature and time for heat treatment can be appropriately set depending on the type of filler 4 and the desired peripheral length envelope.

[0024] In this disclosure, instead of single-grain filler 4 as shown in Figure 1, linked filler 4 as shown in Figure 2 is used as the filler material. Furthermore, it is preferable to pre-grind the raw material for linked filler 4 using a method that can crush the raw material for filler 4 with strong force (for example, a wet planetary ball mill) before mixing it with the raw material for diamond, etc. This makes it possible to crush the coarse linked shape into smaller linked shapes while keeping the perimeter length enveloping degree low.

[0025] If pre-grinding is not performed, there will be a large number of coarsely linked filler 4. As a result, there will be fewer filler 4 with a peripheral length envelope degree of 0.9 to 1. In other words, there will be too many filler 4 with a peripheral length envelope degree of less than 0.9. This will result in the proportion of filler 4 with a peripheral length envelope degree of less than 0.90 exceeding 40%. In contrast, pre-grinding allows the filler 4 to be crushed into smaller linked shapes. As a result, there will be more filler 4 with a peripheral length envelope degree of 0.9 to 1. This will allow the proportion of filler 4 with a peripheral length envelope degree of less than 0.9 to be kept within the range of 10% to 40%.

[0026] When pre-grinding the raw material for filler 4, if the grinding force is too strong, the particles become too small, and the filler 4 gradually approaches single particles (the degree of envelopment approaches 1). If the grinding force is too weak, the particles cannot be made small enough, and the proportion of particles with an envelopment degree of less than 0.9 cannot be sufficiently suppressed. From this viewpoint, it is preferable to control the grinding rotation speed and grinding time.

[0027] As described above, filler raw materials that have been pre-ground in a connected form are mixed with diamond raw materials, a bond, a pore-forming agent, and a binder in a mixer, and then dried and ground to obtain granulated powder. A superabrasive layer is obtained by molding the obtained granulated powder. A wheel is obtained by bonding this superabrasive layer to a base metal and processing it as appropriate.

[0028] Under the above manufacturing conditions, it is preferable that the raw material for filler 4 is crushed so that the filler 4 has a sufficiently small diameter. For example, the average cross-sectional area of ​​filler 4 is 0.09 μm. 2 More than 0.30μm2 The following is desirable: If the diameter of filler 4 is too large, localized areas without superabrasive grains will be created, increasing grinding friction. However, if it is within the specified range, grinding friction can be sufficiently suppressed.

[0029] <How to determine the filler cross-sectional area> The cross-sectional area of ​​the filler is calculated as follows:

[0030] The surface of the sample (superabrasive layer) is highly smoothed (e.g., by ion milling) and observed using a Scanning Electron Microscope (SEM). The magnification of the field of view can be, for example, 5000x. The size of the field of view can be, for example, 24.2 μm x 18.1 μm.

[0031] From the SEM image, an EDS (Energy Dispersive X-ray Spectroscopy) mapping image is obtained, which is color-coded according to elements corresponding to abrasive grains, binder components, filler components, etc.

[0032] The particles of filler 4 are identified from the elemental portions corresponding to the filler components in the EDS mapping image. The area of ​​the contour of the filler 4 particles is measured. For area generation, it is possible to use the area generation function of commercially available software (e.g., Winroof). First, the number of pixels of each contour is determined. Next, the relationship between the number of pixels and length of the scale provided in the electron microscope image is measured. Based on this number, the area of ​​the contour (px) is calculated. 2 to μm 2 Convert to this value. This is calculated for all filler contours, and the sum is obtained. The average cross-sectional area is then divided by the number of contours. For example, the average cross-sectional area can be calculated for 150 fillers.

[0033] Preferably, the volume percentage of superabrasive grains in the superabrasive layer 6 is 2% or more and 25% or less. When the proportion of superabrasive grains is within this range, the cutting performance is particularly excellent and the load during grinding is reduced. More specifically, when the proportion of superabrasive grains is 2 to 25% by volume, it is possible to provide superabrasive grains that are the minimum necessary for material cutting and not excessive.

[0034] Superabrasive grains include, for example, diamond and CBN (cubic boron nitride). In particular, diamond is preferred as the superabrasive grain because it can effectively cut silicon carbide (SiC), which has high hardness. The particle size D50 of the superabrasive grains is preferably, for example, 1 μm or less. When D50 is within this range, high smoothness can be obtained as a grinding wheel for finishing SiC. D50 is also called the median value. D50 is defined as the value at which half of all particles are above this value and the other half are below this value.

[0035] Preferably, the volume ratio of filler 4 is 10% or more and 40% or less. When the volume ratio of filler 4 is within this range, the wear rate becomes particularly low. More specifically, when the volume ratio of filler 4 is 10-40% and has a corresponding peripheral length envelopment, it has a crack propagation suppression effect of the binder in the superabrasive layer 6, can be given sufficient strength as a grinding wheel, and the superabrasive grains can be effectively retained in the binder. Note that the volume ratio of superabrasive grains and filler 4 refers to the volume ratio of each component, such as superabrasive grains, to all components of the superabrasive layer 6, such as superabrasive grains, filler 4, vitrified bond 2, and pores.

[0036] Preferably, the vitrified bond 2 is a glass binder, and the glass binder comprises borosilicate glass containing silicon, boron, and aluminum. The borosilicate glass contains at least one alkali metal and an alkaline earth metal, the alkali metal being at least one selected from the group consisting of lithium, sodium, potassium, and rubidium, and the alkaline earth metal being at least one selected from the group consisting of magnesium, calcium, strontium, and barium. When the material of the glass binder is as described above, if the workpiece is silicon carbide (SiC), the high rigidity of the glass allows for effective cutting into the workpiece while preventing contamination of the workpiece.

[0037] Preferably, the volume percentage of vitrified bond 2 is 2% or more and 10% or less. A volume percentage of vitrified bond 2 within this range is preferable because it optimizes the self-sharpening action, where abrasive grains detach during machining to maintain cutting performance, thereby achieving a balance between cutting performance and wear. A volume percentage of vitrified bond 2 of 3% or more and 6% or less is even more preferable.

[0038] Preferably, the volume ratio of pores 8 is 50% to 80%. A volume ratio of pores 8 within this range is preferable because it ensures an appropriate amount of solid material in the wheel, suppressing excessive wear, while also providing adequate chip pockets for collecting and removing chips generated during machining, thereby maintaining good cutting performance. A volume ratio of pores 8 of 50% to 65% is even more preferable.

[0039] The softening point of vitrified bond 2 is preferably, for example, between 500°C and 900°C. Having a softening point within this range suppresses thermal damage to the diamond abrasive grains during the grinding wheel manufacturing process.

[0040] <How to calculate the circumference envelope> The perimeter-length envelope degree is calculated as follows:

[0041] The surface of the sample (superabrasive layer) is highly smoothed (e.g., by ion milling) and observed using a Scanning Electron Microscope (SEM). The magnification of the field of view can be, for example, 5000x. The size of the field of view can be, for example, 24.2 μm x 18.1 μm.

[0042] From the SEM image, an EDS (Energy Dispersive X-ray Spectroscopy) mapping image is obtained, which is color-coded according to elements corresponding to abrasive grains, binder components, filler components, etc.

[0043] The particles of filler 4 are identified from the elemental portions corresponding to the filler components in the EDS mapping image. The periphery envelope degree is measured for the particles of filler 4. For envelope generation, it is possible to use the envelope generation function of commercially available software (e.g., Winroof). The periphery envelope degrees of 100 or more filler 4 particles can be determined and their arithmetic mean averaged to obtain the periphery envelope degree of filler 4 in the superabrasive layer 6.

[0044] <How to determine the content of various components> The content of various components in a vitrified bond superabrasive wheel is determined as follows.

[0045] The superabrasive layer 6 is filled with resin. Specifically, the pores in the superabrasive layer 6 are filled with resin. The superabrasive layer 6 is highly smoothed (e.g., by ion milling). The smoothed surface is observed using an SEM image. The magnification of the field of view can be, for example, 1000 to 5000 times. The size of the field of view can be, for example, 24.2 μm x 18.1 μm. For example, SEM images can be obtained in five fields of view. EDS mapping images are obtained in the same manner as the measurement of the perimeter envelope. Mapping images are obtained for the five fields of view.

[0046] From the elemental components in the EDS mapping image, the superabrasive grains, filler 4, and vitrified bond 2 (binder) are identified.

[0047] Both the diamond abrasive grains that make up the superabrasive particles and the resin used in the resin embedding process contain carbon, but they can be distinguished by the presence or absence of a contour. Those with a contour are diamond abrasive grains. The resin portion is considered to have pores.

[0048] The area ratio of superabrasive grains, filler 4, vitrified bond, and pores is defined as the volume ratio. The arithmetic mean of the volume ratios in the five fields of view can be used as the content of each component in the superabrasive layer 6.

[0049] [Details of the embodiments of this disclosure] (Example 1) (Wheel manufacturing) Fillers of various shapes and compositions were prepared.

[0050] [Table 1]

[0051] In Table 1, "single grain" in the "raw material shape" column refers to a filler with the shape shown in Figure 1. In the "raw material shape" column, "linked" refers to a filler with the shape shown in Figure 2.

[0052] Of these fillers, samples 3 through 9, 11, and 13 were ground using a wet planetary ball mill (with media). The grinding rotation speed and grinding time are shown in Table 1.

[0053] The filler prepared in Table 1, diamond (particle size 0.5 μm), vitrified bond, porosity-forming agent, and binder were mixed using a mixing mixer. The composition of the vitrified bond is as follows:

[0054] SiO2: 30-60% by mass, Al2O3: 5-20% by mass, B2O3: 10-50% by mass, RO (RO is one or more oxides selected from CaO, MgO, and BaO): 0-15% by mass, R2O (R2O is one or more oxides selected from Li2O, Na2O, and K2O): 0-20% by mass.

[0055] The mixture was dried and pulverized to obtain granulated powder. This granulated powder was then press-molded and fired in an air atmosphere to volatilize the binder and porosity-forming material. Furthermore, the diamond and filler were held in place by a vitrified bond matrix to obtain the superabrasive layers, which formed the structure of vitrified bond superabrasive grinding wheels (samples 1 to 13). The superabrasive layers were then bonded to a base metal and processed into a predetermined shape to form a wheel. A portion of the grinding wheel structure was set aside for observation. (Measurement of periphery envelope) For the vitrified bond superabrasive grinding wheels obtained for observation (sample numbers 1 to 13), the periphery envelope of the filler was measured.

[0056] Step 1: The structure of the grinding wheel was filled with a resin whose main component is carbon, and then polished with a cross-section polisher (manufactured by JEOL Ltd.).

[0057] Step 2: The polished sample was observed using a field emission scanning electron microscope (FE-SEM), and an SEM image (backscattered electron image) was acquired so that 100 to 200 fillers were included in the field of view.

[0058] Step 3: Take EDS mapping images that are color-coded with carbon, aluminum, and silicon within the same field of view. That was a good idea. This applies when measuring aluminum oxide filler; for other filler types, appropriate modifications will be necessary.

[0059] Step 4: The following image analysis was performed using the Winroof software. Binarization was performed on the EDS image of aluminum, and a masking process was applied to paint pixels containing aluminum white in the original SEM image. Aluminum is found in alumina and glass.

[0060] Step 5: The EDS image of carbon was binarized, and pixels containing carbon were masked in black in the original SEM image. This removed the resin and diamond.

[0061] Step 6: Similarly, the silicon EDS image was binarized, and pixels containing silicon were masked in black in the original SEM image. In this process, the glass component overlapped with the aluminum component obtained in Step 4; the overlapping areas were black, while the non-overlapping areas, being alumina, were left white.

[0062] Step 7: The SEM images masked in steps 4 through 6 were binarized to leave the aluminum derived from the filler as white.

[0063] Step 8: Further, perform contour extraction after applying a 5x5 Gaussian filter, and discard any areas smaller than a 20px x 20px square as noise or unclassifiable areas.

[0064] Step 9: Measure the perimeter and envelope perimeter for each colored contour (particle). Note that these perimeter and envelope perimeter are measured automatically using analysis software.

[0065] Step 10: For each contour (particle), calculate the perimeter envelope degree, which is calculated as (envelope perimeter) ÷ (perimeter). This calculation is also performed automatically using the analysis software used in Step 9.

[0066] Step 11: Determine the ratio of the number of particles with a peripheral envelope degree of less than 0.90 to the total number of particles. When silicon dioxide is used as the filler, steps 1 and 2 are the same as when aluminum oxide is used as the filler. Steps 3 through 11 were modified as follows. Step 3: EDS mapping images were acquired that were color-coded with carbon, aluminum, and silicon within the same field of view.

[0067] Step 4: The following image analysis software, Winroof, was used. Binarization was performed on the EDS image of silicon, and a masking process was applied to paint pixels containing silicon white in the original SEM image. Silicon is found in silicon dioxide and glass.

[0068] Step 5: The EDS image of carbon was binarized, and pixels containing carbon were masked in black in the original SEM image. This removed the resin and diamond.

[0069] Step 6: Similarly, the EDS image of aluminum was binarized, and pixels containing aluminum were masked in black in the original SEM image. In this process, the glass component overlapped with the silicon component obtained in Step 4, but the overlapping areas were treated as black, while the non-overlapping areas, being silicon dioxide, were left as white.

[0070] Step 7: The SEM images masked in steps 4 through 6 were binarized to leave silicon from the filler as white.

[0071] Step 8: Further, perform contour extraction after applying a 5x5 Gaussian filter, and discard any areas smaller than a 20px x 20px square as noise or unclassifiable areas.

[0072] Step 9: Measure the perimeter and envelope perimeter for each colored contour (particle). Step 10 For each contour (particle), calculate the perimeter envelope degree, which is calculated as (envelope perimeter) ÷ (perimeter).

[0073] Step 11: Determine the ratio of the number of particles with a peripheral envelope degree of less than 0.90 to the total number of particles. The results are shown in Table 2.

[0074] [Table 2]

[0075] Figure 4 is a schematic diagram of the superabrasive layer 6 of sample number 3. Figure 5 is a schematic diagram of the superabrasive layer 6 of sample number 1.

[0076] In both Figure 4 and Figure 5, the pores 8 in the superabrasive layer 6 were filled with resin. It was confirmed that the filler 4 and superabrasive grains 3 were held in place by the vitrified bond 2.

[0077] Furthermore, Figure 6 shows the relationship between the perimeter length envelope of filler 4 in sample number 3 (shown in Figure 4) and the number of fillers, and the relationship between the perimeter length envelope of filler 4 in sample number 1 (shown in Figure 5) and the number of fillers. Figure 6 is a graph showing the relationship between the perimeter length envelope of filler 4 in sample number 3 (shown in Figure 4) and the number of fillers, and the relationship between the perimeter length envelope of filler 4 in sample number 1 (shown in Figure 5) and the number of fillers. As shown in Figure 6, it was found that in filler 4 of sample number 3 in Figure 4, there were more fillers with a perimeter length envelope of less than 0.90 compared to filler 4 of sample number 1 in Figure 5.

[0078] Furthermore, the cross-section of the uncrushed, interconnected filler 4 was observed. Figure 7 is a photograph of the uncrushed, interconnected filler 4. As shown in Figure 7, it was found that the filler before crushing had a complex shape and was intertwined with each other. (Processing of SiC wafers) Figure 8 shows a superabrasive wheel 20 having a superabrasive layer 6 used for processing SiC wafers. Figure 9 is a cross-sectional view of the superabrasive wheel 20 along the line IX-IX in Figure 8.

[0079] The superabrasive wheel 20 comprises an annular and cup-shaped base metal 120 and a superabrasive layer 6. The superabrasive layer 6 is manufactured using one of the sample numbers 1 to 13 in Table 2. The flat superabrasive layer 6 is fixed to one end face 121 (working surface) of the base metal 120. Multiple superabrasive layers 6 are provided along the circumferential direction of the base metal 120, spaced apart from each other. The bottom surface 113 of the superabrasive layer 6 is fixed to a groove of a predetermined width formed on one end face 121 (working surface) of the base metal 120. Multiple grooves are provided along the circumferential direction of the base metal 120. Each superabrasive layer 6 is fixed to one end face 121 (working surface) of the base metal 120 such that its circumferential end face 111 is approximately parallel to the rotation axis of the superabrasive wheel 20. Each superabrasive layer 6 has a working surface 112 that is substantially perpendicular to the rotation axis of the superabrasive wheel 20. A hole 122 for inserting the rotation axis of the superabrasive wheel 20 is formed in the center of the base metal 120 (working surface).

[0080] Using a superabrasive wheel 20 having a superabrasive layer 6 corresponding to sample numbers 1 to 13, surface machining (C-axis) of a 6-inch diameter SiC wafer is performed. <0001> (The surface perpendicular to the surface was machined.)

[0081] A Fujikoshi RGS34N grinding machine was used. The grinding conditions were as follows: Grinding wheel peripheral speed: 40 m / s Processing thickness: 0.010mm Feed rate: 0.018 mm / min Coolant: Pure water The above grinding was performed using the grinding method 100 shown in Figure 10. Figure 10 is a schematic diagram of the superabrasive wheel 20 and table 110 shown to illustrate the grinding method using the superabrasive wheel 20.

[0082] More specifically, in the grinding method 100, the workpiece 130, which is a SiC wafer, is fixed on the table 110. Here, the table 110 is rotatable in the direction indicated by arrow 110R. The superabrasive wheel 20 is rotatable in the direction indicated by arrow 1R. Furthermore, the direction indicated by arrow 1F is the cutting direction.

[0083] During the grinding process, the wear rate (change in the height of the superabrasive layer 6 before and after grinding / change in the thickness of the workpiece (wafer) in the ground portion before and after grinding), the load current value for rotating the superabrasive wheel, and the load for rotating the superabrasive wheel were measured. These results are shown in Table 2.

[0084] Sample No. 1, being composed of single-grain fillers, was prone to cracking in the superabrasive layer, resulting in a high wear rate.

[0085] Sample No. 2 used a linked filler, and because it was not crushed, the superabrasive grains and filler separated, resulting in a large area consisting only of filler. Consequently, the wear rate was high. In other words, the abrasive grains did not diffuse sufficiently between the fillers, and the grinding performance was not achieved.

[0086] In sample number 3, the grinding time was short, causing the superabrasive grains and filler to separate, similar to sample number 2, resulting in a large portion consisting only of filler. Consequently, the wear rate was high.

[0087] In sample number 9, the grinding time was too long, resulting in excessive grinding and the connected filler particles becoming closer to single particles. Consequently, the percentage of particles with a perimeter envelope degree of less than 0.90 was 3%, leading to a high abrasion rate.

[0088] Samples 10 and 11 both contain silicon carbide fillers. Sample 11, which has a connected filler shape and has a perimeter length envelope degree of less than 0.90 in the range of 10-40%, showed superior results in load current value, load, and wear rate compared to sample 10, which has a perimeter length envelope degree of less than 0.90 in 1% of samples.

[0089] Samples 12 and 13 both contain silicon dioxide fillers. Sample 13, which has a connected filler shape and where the percentage of perimeter length envelopes less than 0.90 is in the range of 10-40%, showed superior results in load current value, load, and wear rate compared to sample 12, where the percentage of perimeter length envelopes less than 0.90 is 0%.

[0090] (Example 2) (Relationship between the ratio of diamond and filler and grinding performance) We investigated how the ratio of diamond to filler affects grinding performance.

[0091] Samples 40 to 58 were prepared in which the ratio of diamond and filler in sample 4 was varied in the same manner as in Example 1.

[0092] The same SiC wafer processing tests as in Example 1 were performed on these samples. The results are shown in Table 3.

[0093] [Table 3]

[0094] The results from samples 41 to 44 showed that favorable results can be obtained when the diamond content is between 2 and 25 volume percent.

[0095] Results from samples 46 to 50 showed that in sample 46, where the filler content was less than 10 vol%, and in sample 50, where the filler content was greater than 40 vol%, either the load or the wear rate was worse compared to samples 47 to 49. Therefore, it was found that favorable results can be obtained when the filler content is within the range of 10 to 40 vol%.

[0096] From the results for sample numbers 51 to 56, it was found that the most favorable results were obtained when the diamond content was in the range of 2 to 25 volume percent and the filler content was in the range of 10 to 40 volume percent.

[0097] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope. [Explanation of Symbols]

[0098] 2 Vitrified bond, 3 Superabrasive grains, 4 Filler, 6 Superabrasive grain layer, 7 Crack, 8 Pore, 12 Superabrasive grain layer, 20 Superabrasive wheel, 110 Table, 111 Circumferential end face, 112 Working surface, 113 Bottom surface, 120 Base metal, 121 One end face, 122 Hole, 130 Workpiece.

Claims

1. A superabrasive layer comprising superabrasive grains, fillers, and a vitrified bond, having pores formed therein, The filler is at least one of Al₂O₃, SiO₂, and SiC. A vitrified bond superabrasive wheel in which the proportion of fillers with a peripheral length envelopment degree of less than 0.90 is 15% or more and 40% or less.

2. The vitrified bond superabrasive wheel according to claim 1, wherein the volume ratio of the superabrasive grains in the superabrasive layer is 2% or more and 25% or less.

3. The vitrified bond superabrasive wheel according to claim 1 or claim 2, wherein the volume ratio of the filler in the superabrasive layer is 10% or more and 40% or less.

4. The vitrified bond superabrasive wheel according to claim 1 or claim 2, wherein the vitrified bond comprises a glass binder, the glass binder comprises borosilicate glass containing silicon, boron, and aluminum, the borosilicate glass comprises at least one of an alkali metal and an alkaline earth metal, the alkali metal being at least one selected from the group consisting of lithium, sodium, potassium, and rubidium, and the alkaline earth metal being at least one selected from the group consisting of magnesium, calcium, strontium, and barium.

5. The aforementioned filler is Al ２ O ３ A vitrified bond superabrasive wheel according to claim 1 or claim 2.

6. The vitrified bond superabrasive wheel according to claim 1 or claim 2, wherein the superabrasive grains are made of diamond.

7. The vitrified bond superabrasive wheel according to claim 1 or claim 2, wherein the volume ratio of the vitrified bond is 2% or more and 10% or less.

8. The vitrified bond superabrasive wheel according to claim 1 or claim 2, wherein the volume ratio of the pores is 50% or more and 80% or less.

9. The average cross-sectional area of ​​the filler is 0.09 μm ２ 0.30 μm or more ２ The vitrified bond superabrasive wheel according to claim 1 or claim 2, which is as follows:

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