Method for manufacturing vitrified grinding stone, abrasive material used therefor and vitrified grinding stone

Abstract

To provide a method for manufacturing a vitrified grinding stone capable of improving grinding stone strength.SOLUTION: A method for manufacturing a vitrified grinding stone disclosed herein includes: a step (A) of providing an abrasive material in which glass flux 14 is attached to a surface of each abrasive grain; and a step (B) of sintering a mixture including the abrasive material and a vitrified bond. The step (B) is characterized in that the glass flux 14 and the vitrified bond are made to react with each other to promote melting or softening of the vitrified bond in the vicinity of the surface of the abrasive grain 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a vitrified grinding wheel, an abrasive material used therefor, and a vitrified grinding wheel. [Background technology]

[0002] Grinding wheels, in which abrasive grains are bonded with a bonding agent, are used as grinding tools for finishing the surfaces and cross sections of metal materials, etc. Known types of such grinding wheels, depending on the type of bonding agent, include vitrified grinding wheels, resinoid grinding wheels, and metal grinding wheels.

[0003] In the above-mentioned grinding wheels, depending on the combination of abrasive grains and binder, the wettability and adhesion between the abrasive grains and binder tend to be poor, resulting in insufficient grinding wheel strength and insufficient grain retention. To address this issue, it has been proposed to improve grinding wheel strength and grain retention by coating the abrasive grains with a material other than the abrasive grains themselves. For example, Patent Document 1 discloses that the surface of cubic boron nitride (hereinafter also referred to as "CBN") is coated with an aluminum oxide layer or a silicon oxide layer, thereby improving grain retention. Patent Document 2 discloses that the surface of superabrasive grains such as diamond or CBN is coated with a particulate oxide to improve grain retention through an anchoring effect. Furthermore, Patent Document 3 discloses that the surface of superabrasive grains is coated with a ceramic material other than an oxide to improve the grain retention of the grinding wheel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-108461 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-12545 [Patent Document 3] Japanese Patent Application Publication No. 4-331076 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when using the method described in Patent Document 2, the coating can create unevenness on the surface of the abrasive grains, which can reduce the fluidity of the abrasive grains, for example, when mixing the abrasive grains with the binder. Furthermore, as described in Patent Document 1, coating the surface of the abrasive grains with a layer of aluminum oxide or silicon oxide can increase the softening point of the binder or promote its crystallization, which can affect the properties of the abrasive grains and reduce their grain retention. Furthermore, as described in Patent Document 3, CBN can improve the wetting of the abrasive grains with the vitrified bond by reacting with them, but this can lead to the problem of grain loss. Furthermore, Patent Document 3 also describes that when boron oxide is generated between the abrasive grains and the vitrified bond due to the reaction between them, the strength of the boron oxide is quite low and its adhesion to the abrasive grains is weak, resulting in reduced grain retention. Therefore, there is still room for improvement in terms of improving grinding wheel strength and grain retention.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a vitrified grinding wheel that improves the strength of the grinding wheel, an abrasive material used therefor, and a vitrified grinding wheel with improved strength. [Means for solving the problem]

[0007] The method for manufacturing a vitrified grinding wheel disclosed herein includes the steps of: (A) preparing an abrasive having a glass flux attached to the surface of the abrasive grains; and (B) firing a mixture containing the abrasive and a vitrified bond. The step (B) is characterized by reacting the glass flux with the vitrified bond to promote melting or softening of the vitrified bond near the surface of the abrasive grains.

[0008] By using an abrasive material with a glass flux attached to the surface of the abrasive grains in the manufacture of a vitrified grinding wheel, the glass flux promotes melting and softening of the vitrified bond in the vicinity of the abrasive grains when the mixture of the abrasive material and the vitrified bond is fired. As a result, after the manufacture of the grinding wheel, the abrasive grains are suitably held in the vitrified bond, making it possible to provide a vitrified grinding wheel with high grinding wheel strength.

[0009] In a preferred embodiment of the manufacturing method disclosed herein, step (B) is performed under firing conditions such that the glass flux contained in the abrasive prepared in step (A) does not remain in its original composition and shape. According to this configuration, the fluidity of the vitrified bond near the surface of the abrasive grains can be more suitably increased, and the reduction in strength due to the glass flux remaining in the manufactured grinding wheel 100 can be suppressed, thereby providing a grinding wheel with high strength.

[0010] In a preferred embodiment of the manufacturing method disclosed herein, step (A) includes a mixing treatment of mixing the abrasive grains with the glass flux or a material containing the glass flux. According to this configuration, the glass flux can be adhered to the surface of the abrasive grains in an appropriate manner.

[0011] In a preferred embodiment of the manufacturing method disclosed herein, step (A) includes a firing treatment of firing the abrasive material having the glass flux adhered to the surface of the abrasive grains, and in a preferred embodiment of such firing treatment, firing is carried out at a temperature of 150°C or higher and 1000°C or lower. According to this configuration, the glass flux adhering to the surface of the abrasive grains can be stabilized.

[0012] In a preferred embodiment of the production method disclosed herein, the firing in step (B) is carried out at a temperature of 300°C or higher and 1000°C or lower. According to this configuration, it is possible to provide a vitrified grinding wheel having high grinding wheel strength without affecting the properties of the abrasive grains.

[0013] In a preferred embodiment of the manufacturing method disclosed herein, in the step (B), the ratio (Y / X) of the weight Y of the glass flux to the weight X of the vitrified bond is 0.1 or less. According to this configuration, it is possible to improve the wetting of the abrasive grains with the vitrified bond without affecting the grinding function of the abrasive grains.

[0014] Furthermore, the technology disclosed herein provides an abrasive material used in the manufacture of a vitrified grinding wheel. The abrasive material disclosed herein includes abrasive grains and a glass flux adhered to the surfaces of the abrasive grains. The abrasive material has a volumetric amount of the glass flux adhered per unit surface area of the abrasive grains of 0.2 mm 3 / m 2 More than 50mm 3 / m 2 The following is the result. According to this configuration, when manufacturing a vitrified grinding wheel, the glass flux improves the fluidity of the vitrified bond near the surface of the abrasive grains, thereby favorably forming a network between the abrasive grains and the vitrified bond regardless of the properties of the abrasive grains, and providing a grinding wheel with high grinding wheel strength.

[0015] In a preferred embodiment of the abrasive material disclosed herein, the glass flux is a compound containing at least one element selected from the group consisting of boron, lead, fluorine, alkali metal elements, and alkaline earth metal elements. According to this configuration, when a mixture of an abrasive material and a vitrified bond is fired to manufacture a grinding wheel, melting of the vitrified bond, which is a vitreous binder, can be suitably promoted.

[0016] In a preferred embodiment of the abrasive material disclosed herein, the abrasive grains are either diamond or cubic boron nitride. According to this configuration, the effect of improving the abrasive grain retention force by providing the glass flux on the surface of the abrasive grains is more suitably exhibited.

[0017] In a preferred embodiment of the abrasive material disclosed herein, the glass flux is partially attached to the surface of the abrasive grains. With this configuration, the abrasive grains can be made to exhibit their grinding function in an optimal manner.

[0018] In a preferred embodiment of the abrasive material disclosed herein, the BET specific surface area A (m 2 / g) to the BET specific surface area B (m 2 / g) ratio (B / A) is 1.3 or less. According to this configuration, the abrasive and the vitrified bond are mixed appropriately, and the vitrified bond can be easily melted and softened near the surfaces of the abrasive grains.

[0019] In a preferred embodiment of the abrasive material disclosed herein, the amount of glass flux deposited per unit area of the abrasive grains (mg / m 2 ) is 0.02 mg / m 2 More than 50mg / m 2 In another preferred embodiment, the content of the glass flux is 10 wt % or less when the entire abrasive is taken as 100 wt %. According to this configuration, the wetting between the abrasive grains and the vitrified bond can be improved without reducing the grinding function of the abrasive grains.

[0020] The technology disclosed herein also provides a vitrified grinding wheel. The vitrified grinding wheel disclosed herein includes a plurality of abrasive grains and a vitrified bond that bonds the plurality of abrasive grains to one another. The concentration of a glass flux component at a position P1 where the abrasive grains and the vitrified bond contact each other is higher than the concentration of a glass flux component at a position P2 where the abrasive grains and the vitrified bond do not contact each other. Here, the glass flux component is at least one of boron, lead, fluorine, an alkali metal element, and an alkaline earth metal element. According to this configuration, the above-mentioned effects are preferably exhibited, and a vitrified grinding wheel with high grinding wheel strength can be realized.

[0021] In a preferred embodiment of the vitrified grinding wheel disclosed herein, the softening point of the vitrified bond at position P1 where the abrasive grains and the vitrified bond contact each other is lower than the softening point of the vitrified bond at position P2 where the abrasive grains and the vitrified bond do not contact each other. According to this configuration, the effect of including a plurality of abrasive grains with a glass flux adhered to the surface is preferably exerted, and a vitrified grinding wheel with high grinding wheel strength can be realized. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram schematically illustrating an abrasive grain having a glass flux attached to its surface according to one embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating the structure of a grindstone according to one embodiment. [Figure 3] FIG. 3 is an SEM image (150x) of Example 1. [Figure 4] FIG. 4 is an SEM image (150x) of Example 2. [Figure 5] FIG. 5 is an SEM image (150x) of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention are described below. Matters necessary for implementing the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. In this specification, the notation "A to B" indicating a numerical range means "A or more and B or less" unless otherwise specified. The drawings are schematic, and the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships. Furthermore, the term "dispersion" in this specification refers to a mixture in which some or all of the solid components are dispersed in a liquid dispersion medium, and includes so-called "pastes," "slurries," "inks," etc., regardless of dispersion stability.

[0024] FIG. 1 is a diagram schematically illustrating abrasive grains 12 having a glass flux 14 attached to their surfaces. FIG. 2 is a diagram schematically illustrating the structure of a grinding wheel 100. The abrasive material disclosed herein includes abrasive grains 12 and a glass flux 14 attached to the surfaces of the abrasive grains 12. The grinding wheel 100 disclosed herein also includes a plurality of abrasive grains 12 and a vitrified bond 20 that bonds the plurality of abrasive grains 12 to one another. The grinding wheel 100 can be produced by firing a mixture of an abrasive material and a bond (here, the vitrified bond 20) at an appropriate temperature. When manufacturing the grinding wheel 100, using an abrasive material having a glass flux 14 attached to the surfaces of the abrasive grains 12 can enhance wetting between the abrasive grains 12 and the vitrified bond 20. Furthermore, when firing the mixture of the abrasive and the vitrified bond 20, the glass flux 14 promotes the melting and softening of the vitrified bond 20, which allows the vitrified bond 20 to flow favorably in the vicinity of the abrasive grains 12, thereby improving the abrasive grain retention force in the fired grinding wheel 100. This improves the grinding wheel strength of the grinding wheel 100. The abrasive material and grinding wheel 100 disclosed herein will now be described.

[0025] <Abrasive material> The abrasive material includes abrasive grains 12. The abrasive grains 12 function to directly grind the workpiece. The properties of the abrasive grains 12 are not particularly limited and may be appropriately selected depending on the purpose of the grinding process, the mode of use, and other factors. The abrasive grains 12 can be determined taking into account the physical properties, such as the hardness, of the workpiece. Examples of the abrasive grains 12 include particles made of minerals, metals, or semimetals, such as carbides, oxides, and nitrides. Specific examples include diamond, cubic boron nitride (hereinafter also referred to as "CBN"), silica, alumina, and ceria. Among these, diamonds with a Knoop hardness of 4000 or more (Knoop hardness: approximately 7000 to 8000) and CBN (Knoop hardness: approximately 4700) are preferably used. The diamond may be natural or artificial. For example, artificial diamonds are preferred because they are easily obtained in high purity and various types of artificial diamonds are readily available as materials.

[0026] The shape of the abrasive grains 12 is not particularly limited and may be, for example, spherical, plate-like, or irregularly shaped. The size of the abrasive grains 12 can also be determined appropriately depending on the purpose and manner of use of the grinding wheel 100. For example, the average particle size of the abrasive grains 12 may be approximately 0.1 μm or more and 1000 μm or less, and preferably approximately 1 μm or more and 100 μm or less. Furthermore, although not particularly limited, the average aspect ratio (ratio of major axis to minor axis) of the abrasive grains 12 is preferably 1 or more and 2 or less, and more preferably 1.1 or more and 1.8 or less. The average particle size of the abrasive grains can be determined, for example, by microscopic observation. Specifically, the abrasive grains are observed using a microscope (optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM)), and the equivalent circle diameters of a predetermined number (e.g., 100) or more abrasive grains in the resulting image are determined by image analysis, and the arithmetic mean value of these diameters can be used as the average particle size of the abrasive grains. The average aspect ratio can be determined as follows: In the resulting image, the smallest rectangle circumscribing each particle is drawn, and the length of the long side (major axis) and the length of the short side (minor axis) of the rectangle are determined. The value obtained by dividing the major axis by the minor axis (major axis / minor axis) is then calculated, and the arithmetic mean value is calculated, thereby determining the average aspect ratio of the abrasive grains.

[0027] Although not particularly limited, the BET specific surface area (m 2 / g) is, for example, 0.01m 2 / g or more 100m 2 / g or less, and 2 / g or more 10m 2 / g or less. In this specification, the "BET specific surface area of the abrasive grains" refers to a value obtained by analyzing, by the BET method, an adsorption isotherm measured by a gas adsorption method using nitrogen (N) gas as the adsorbate.

[0028] The abrasive material disclosed herein contains a glass flux 14. Here, the glass flux is a flux component that promotes the melting and softening of the vitrified bond 20. In other words, the glass flux 14 is a component that exhibits the effect of increasing the softening and fluidity of the vitrified bond 20. When manufacturing the grinding wheel 100, by using an abrasive material having the glass flux 14 adhered to the surfaces of the abrasive grains 12, the vitrified bond 20 and the glass flux 14 react with each other, making it easier for the vitrified bond 20 to melt and soften near the surfaces of the abrasive grains 12. This increases the fluidity of the vitrified bond 20 near the surfaces of the abrasive grains 12, allowing for the favorable formation of a network. This improves the grain retention and the grinding wheel strength of the grinding wheel 100.

[0029] Examples of such glass flux 14 include compounds containing boron (B), lead (Pb), fluorine (F), alkali metal elements, alkaline earth metal elements, etc. For example, oxides, hydroxides, carbonates, nitrates, fluorides, organometallic compounds, and resinates containing these elements can be preferably used. More specifically, examples of the glass flux 14 include oxides such as boron oxide (BO), lithium oxide (LiO), potassium oxide (KO), barium oxide (BaO), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), and lead oxide (PbO); hydroxides such as potassium hydroxide (KOH) and sodium hydroxide (NaOH); fluorides such as lithium fluoride (LiF), sodium fluoride (LiNa), and calcium fluoride (CaF); carbonates such as sodium carbonate (NaO), potassium carbonate (KCO), and magnesium carbonate (MgCO); nitrates such as sodium nitrate (NaNO) and potassium nitrate (KNO); and boron-containing compounds such as boric acid (B(OH)) and borax (NaBO). The glass flux 14 may be composed of one of the above-described glass flux components, or a mixture of two or more of them.

[0030] The BET specific surface area (m 2 / g) is, for example, 0.01m 2 / g or more 100m 2 / g or less, and 2 / g or more 10m 2 / g or less. In the abrasive material disclosed herein, the BET specific surface area A (m 2 / g) versus the BET specific surface area B(m 2The ratio (B / A) of the glass flux 14 to the surface of the abrasive grains 12 (g) is preferably 1.3 or less, and may be 1.2 or less, or may be 1.1 or less. In other words, even if the glass flux 14 adheres to the surface of the abrasive grains 12, it is preferable that the surface unevenness of the abrasive grains 12 does not increase significantly. With this configuration, when manufacturing the grinding wheel 100, the abrasive material and the vitrified bond 20 are suitably mixed, and in the firing stage of the mixture, the vitrified bond 20 can be easily melted and softened near the surface of the abrasive grains 12.

[0031] The content of the glass flux is preferably 10 wt% or less, assuming the entire abrasive to be 100 wt%. The content of the glass flux is more preferably 7 wt% or less, and even more preferably 5 wt% or less, and may be 3 wt% or less, 2 wt% or less, 1 wt% or less, or 0.8 wt% or less. This improves the wetting between the abrasive and the vitrified bond 20 without reducing the grinding function of the workpiece. Furthermore, the abrasive grain retention force of the grinding wheel 100 can be improved without affecting the properties of the vitrified bond 20. On the other hand, if the content of the glass flux is too low, the above-mentioned effects will not be fully exhibited. Therefore, the content of the glass flux is preferably 0.05 wt% or more, and may be 0.1 wt% or more, or 0.5 wt% or more, for example. The content of the glass flux in the entire abrasive can be determined, for example, by dissolving and removing the glass flux, and quantifying the glass flux component contained in the solution by ICP emission analysis or the like.

[0032] Amount of glass flux attached per unit surface area of abrasive grain (mg / m 2 ) is 0.02 mg / m from the viewpoint of sufficiently improving the fluidity of the vitrified bond 20 on the surface of the abrasive grains 12. 2 It is preferable that the concentration is 0.05 mg / m or more. 2 It may be 0.1 mg / m or more. 2 It may be 1.5 mg / m or more. 2On the other hand, if an excessive amount of glass flux 14 adheres to the surface of the abrasive grains 12, there is a possibility that an excessive amount of glass flux will remain in the manufactured grinding wheel 100, which may reduce the strength and workability. From these viewpoints, the amount of glass flux adhered per unit surface area of the abrasive grains is 50 mg / m 2 Preferably, it is 30 mg / m or less. 2 may be less than 25 mg / m 2 More preferably, it is 5 mg / m or less. 2 may be less than 4 mg / m 2 More preferably, it is 3 mg / m or less. 2 The amount of glass flux attached per unit surface area of abrasive grain (mg / m 2 ) can be determined from the content of the glass flux and the BET specific surface area of the abrasive grains.

[0033] In addition, the amount of glass flux attached per unit surface area of the abrasive grain (in terms of volume) (mm 3 / m 2 ) is set to 0.2 mm from the viewpoint of sufficiently improving the fluidity of the vitrified bond 20 on the surface of the abrasive grains 12. 3 / m 2 It is preferable that the thickness is 0.4 mm or more. 3 / m 2 It may be more than 0.7mm 3 / m 2 It may be more than 1 mm 3 / m 2 On the other hand, if an excessive amount of glass flux 14 adheres to the surface of the abrasive grains 12, there is a possibility that an excessive amount of glass flux will remain in the manufactured grinding wheel 100, which may reduce the strength and workability. Therefore, the amount of glass flux adhered in volume terms per unit surface area of the abrasive grains is 50 mm 3 / m 2 Preferably, it is less than 30 mm 3 / m 2 May be less than 20mm 3 / m 2 May be less than 15mm 3 / m 2May be less than 14mm 3 / m 2 It is more preferable that it is 5 mm or less. 3 / m 2 May be less than 3mm 3 / m 2 It is more preferable that the amount of glass flux attached per unit surface area of the abrasive grain (in terms of volume) is less than 1 / 2 mm. 3 / m 2 ) can be determined from the volumetric content of the glass flux calculated from the weight and density of the constituent components of the abrasive and the BET specific surface area of the abrasive grains.

[0034] The glass flux 14 is fixed to the surface of the abrasive grains 12, for example. The shape and form of the glass flux 14 when attached to the surface of the abrasive grains 12 are not particularly limited. For example, the shape of the glass flux 14 on the surface of the abrasive grains 12 may be particulate or film-like. If the glass flux 14 is attached in particulate form, irregularities of approximately 0.05 μm to 300 μm may occur on the surface of the abrasive grains 12, reducing the flowability of the powder. For this reason, from the viewpoint of mixing with the vitrified bond 20 and moldability, it is preferable that the shape of the glass flux 14 when attached to the surface of the abrasive grains 12 is film-like. Furthermore, the glass flux 14 may exist in the form of an amorphous structure on the surface of the abrasive grains 12. Alternatively, the amorphous structure may form a skeleton, and various metal elements (or semi-metal elements) may exist within the skeleton as oxides or cations (hereinafter also referred to as an "amorphous matrix structure"). The form of the glass flux 14 can be confirmed by observation under a microscope.

[0035] The glass flux 14 may be adhered to the entire surface of the abrasive grain 12, or may be adhered only partially to the surface of the abrasive grain 12. Preferably, the glass flux 14 is adhered only partially to the surface of the abrasive grain 12. For example, as shown in FIG. 1, the glass flux 14 may be present in the form of islands (i.e., scattered) on the surface of the abrasive grain 12. This prevents the glass flux from covering the entire surface of the abrasive grain 12 that is not in contact with the vitrified bond 20 in the manufactured grinding wheel 100, thereby enabling the grinding wheel 100 to exhibit optimal processing performance (e.g., cutting function). The scattered presence of the glass flux 14 on the surface of the abrasive grain 12 can be confirmed by a conventionally known method. For example, this can be confirmed by observing the surface or cross section of the abrasive grain using an electron microscope.

[0036] If the average thickness of the glass flux 14 is too thick, irregularities that cause an anchoring effect on the surface of the abrasive grains 12 may occur, hindering the fluidity of the abrasive. Therefore, the average thickness of the glass flux 14 is preferably, for example, 30 nm or less, and may be 20 nm or less, more preferably 15 nm or less, or even 10 nm or less. On the other hand, if the thickness is too thin, the effect of the glass flux 14 in improving the wetting between the abrasive grains 12 and the vitrified bond 20 is not fully realized. For example, the average thickness of the glass flux 14 is preferably 0.1 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. The thickness of the glass flux 14 can be determined, for example, using the volume ratio of the abrasive grains to the glass flux and the BET specific surface area of the abrasive grains. Alternatively, the thickness can be determined by calculating the average thickness of the glass flux at multiple locations (e.g., 10 locations) arbitrarily selected on an elemental map of the constituent elements (e.g., boron) of the glass flux on the cross section of the abrasive.

[0037] In a preferred embodiment, the abrasive grains are made of diamond, and a glass flux is attached to the surface of the diamond abrasive grains. When diamond is used as the abrasive grains, it is necessary to sinter at a relatively low temperature (for example, 700°C or less) to prevent the diamond from oxidizing. In addition, the wettability between diamond and the vitrified bond 20, which is an oxide, tends to be low. In contrast, by attaching a glass flux to the surface of the diamond abrasive grains, it is possible to promote the melting and softening of the vitrified bond 20 even when sintered at a relatively low temperature. Therefore, when the abrasive grains are made of diamond, the effect of having a glass flux attached to the surface can be more pronounced.

[0038] In another preferred embodiment, the abrasive grains are made of cubic boron nitride (CBN), and a glass flux is attached to the surface of the CBN abrasive grains. When the abrasive grains are made of CBN, there is a risk that the CBN will react with the vitrified bond 20 when mixed with the vitrified bond 20 and fired, resulting in the abrasive grains being worn down. Furthermore, boron oxide may be generated at the interface between the abrasive grains and the vitrified bond 20, reducing the abrasive grain retention. By attaching a glass flux to the surface of the CBN abrasive grains, the glass flux reacts more actively with the vitrified bond 20 during heat treatment, for example, to manufacture the grinding wheel 100, thereby preventing the abrasive grains (CBN) from being worn down. In this case, the glass flux preferably contains a boron-containing compound. This more effectively prevents boron from diffusing from the CBN abrasive grains (CBN) to the vitrified bond 20.

[0039] The technology disclosed herein provides an abrasive (powder material) for use in manufacturing vitrified grinding wheels. The abrasive (powder material) is preferably substantially composed of abrasive grains 12 having glass flux 14 attached to their surfaces. Here, "substantially composed" means that the abrasive grains 12 having glass flux 14 attached to their surfaces are present in a significant proportion, and means that they account for 60% by number or more, 80% by number or more, more preferably 90% by number or more, and even more preferably 95% by number or more of the total abrasive grains that make up the abrasive (powder material).

[0040] <Grinding stone> 2, the grinding wheel 100 includes a plurality of abrasive grains 12 and a vitrified bond 20, and is configured by bonding the abrasive grains 12 together via the vitrified bond 20. The grinding wheel 100 is also a porous body having a plurality of voids 30. These voids 30 function as spaces for temporarily storing grinding chips generated when a workpiece is ground.

[0041] The vitrified bond 20 is a bonding agent that bonds the plurality of abrasive grains 12 to one another. As the vitrified bond 20, any conventionally known vitrified bond can be used without any particular limitation. For example, the vitrified bond 20 is a vitreous bonding agent whose main components are Bi2O3-ZnO-B2O3-SiO2-based glass, SiO2-RO (R represents, for example, Mg, Ca, Zn, Ba, or Sr; the same applies below), SiO2-R'2O (R' represents, for example, Li, K, or Na; the same applies below), SiO2-RO-Al2O3-based glass, SiO2-RO-Bi2O3-based glass, SiO2-RO-Y2O3-based glass, SiO2-RO-B2O3-based glass, SiO2-Al2O3-based glass, SiO2-ZnO-based glass, SiO2-ZrO2-based glass, RO-R'2O-based glass, RO-based glass, lead-based glass, lead-lithium-based glass, borosilicate-based glass, etc. Note that the vitrified bond 20 may contain one or more components in addition to the above-mentioned glass components. Furthermore, one of the above glass components may be used alone, or two or more of them may be used in combination.

[0042] In the grinding wheel 100, the concentration of the glass flux component differs between a position P1 where the abrasive grains 12 and the vitrified bond 20 contact each other and a position P2 where the abrasive grains 12 and the vitrified bond 20 do not contact each other. Here, the "glass flux component" refers to at least one of boron, lead, fluorine, an alkali metal element, and an alkaline earth metal element. Preferably, in the grinding wheel 100, the concentration of the glass flux component at the position P1 where the abrasive grains 12 and the vitrified bond 20 contact each other is lower than the concentration of the glass flux component at the position P2 where the abrasive grains 12 and the vitrified bond 20 do not contact each other. The concentration may have a concentration gradient that decreases stepwise or continuously from the position P1 where the abrasive grains 12 contact each other to the position P2 where the abrasive grains 12 do not contact each other. This allows the abrasive grains 12 to be properly held in the vitrified bond 20.

[0043] As an example, let us consider a case where the glass flux component is boron. In this case, the boron concentration at position P1 where the abrasive grain and the vitrified bond contact each other is preferably lower than the boron concentration at position P2 where the abrasive grain and the vitrified bond do not contact each other. Specifically, for example, point a is the surface of the abrasive grain, and point b is a point located in an area not in contact with the abrasive grain, at least 3 μm away from point a and at least 3 μm away from other abrasive grains. In this case, the boron concentration B at point b is lower than the boron concentration A at point a (concentration A > concentration B). For example, the ratio of the boron concentration A at point a to the boron concentration B at point b (concentration A / concentration B) is preferably 1.1 or greater, but may also be 1.2 or greater, or 1.3 or greater. The boron concentration at each point can be measured using an EPMA (electron probe microanalyzer). Furthermore, although the above description has been given as an example in which the glass flux component is boron, the same applies to cases in which the glass flux component is lead (Pb), fluorine (F), an alkali metal element, an alkaline earth metal element, or the like.

[0044] In the grinding wheel 100, it is preferable that the softening point of the vitrified bond 20 be different between a position P1 where the abrasive grains 12 and the vitrified bond 20 contact each other and a position P2 where the abrasive grains 12 and the vitrified bond 20 do not contact each other. Specifically, in the grinding wheel 100, it is preferable that the softening point of the vitrified bond 20 at the position P1 where the abrasive grains 12 and the vitrified bond 20 contact each other is lower than the softening point of the vitrified bond 20 at the position P2 where the abrasive grains 12 and the vitrified bond 20 do not contact each other. For example, the surface of the abrasive grain 12 is defined as point a, and a point located in an area not in contact with the abrasive, which is 3 μm or more away from point a and 3 μm or more away from other abrasive grains is defined as point b. In this case, the softening point A of the vitrified bond at point a is lower than the softening point B of the vitrified bond at point b (softening point A<softening point B). For example, the difference between the softening point A of the vitrified bond at point a and the softening point B of the vitrified bond at point b is preferably 10°C or more, and may be 30°C or more, or even 50°C or more. The softening point of the vitrified bond at each point can be determined by measuring a bond that reproduces the composition of points a and b using a TMA (thermomechanical analyzer). The composition of points a and b can be measured using an EPMA.

[0045] In the grinding wheel 100, the proportion of abrasive grains 12 in the entire grinding wheel (i.e., the sum of the abrasive grains 12 and the vitrified bond 20) can be appropriately set depending on the application of the grinding wheel. If the proportion of abrasive grains 12 is too low, it is undesirable because it can reduce grinding efficiency. On the other hand, if the proportion of abrasive grains 12 is too high, the proportion of the vitrified bond 20 decreases relatively, and the abrasive grains 12 are not properly fixed. This is undesirable because it can cause the abrasive grains 12 to fall off, the vitrified bond 20 to crack, and the durability to decrease. Therefore, the proportion of abrasive grains 12 in the entire grinding wheel is preferably 5 wt% or more and 90 wt% or less, and may be, for example, 20 wt% or more and 80 wt% or less. The grinding wheel 100 disclosed herein may contain additives such as dispersants and foaming agents, or decomposition products thereof, within the scope of the present invention.

[0046] <Method of manufacturing grindstones> Next, an example of a method for manufacturing the vitrified grinding wheel disclosed herein will be described. This manufacturing method includes at least step (A) of preparing an abrasive material in which a glass flux 14 is adhered to the surfaces of abrasive grains 12, and step (B) of firing a mixture containing the abrasive material and a vitrified bond 20. The manufacturing method disclosed herein is characterized in that in step (B), the glass flux 14 and the vitrified bond 20 are reacted to promote melting or softening of the vitrified bond 20 near the surfaces of the abrasive grains 12; otherwise, the manufacturing process may be the same as conventional methods. Furthermore, the manufacturing method disclosed herein may include other steps at any stage.

[0047] In step (A), an abrasive material is prepared in which glass flux 14 is adhered to the surfaces of abrasive grains 12. Step (A) is not particularly limited as long as it is possible to adhere glass flux 14 to the surfaces of abrasive grains 12. For example, glass flux 14 can be adhered to the surfaces of abrasive grains 12 by mixing abrasive grains 12 with glass flux 14 or a material containing a glass flux. Alternatively, glass flux 14 can be adhered to the surfaces of abrasive grains 12 by gas phase methods such as CVD (Chemical Vapor Deposition) and PVD (Physical Vapor Deposition), liquid phase reduction, hydrothermal synthesis, coprecipitation, or the like.

[0048] Here, as an example of step (A), a process of adhering the glass flux 14 to the surface of the abrasive grains 12 by mixing the abrasive grains 12 with the glass flux 14 or a material containing the glass flux will be described. For example, step (A) may include a mixing process (hereinafter also referred to as a "first mixing process") in which a liquid medium is mixed with the abrasive grains 12 and the glass flux 14 or a material containing the glass flux, and a preheating process in which the liquid medium is removed after the first mixing process. The method for mixing the materials in the first mixing process is not particularly limited, and can be performed using various known mixing devices, such as a three-roll mill, a magnetic stirrer, a planetary mixer, or a disperser. The preheating process is not particularly limited as long as it can remove the liquid medium. For example, heating at a temperature of approximately 50°C to 150°C for approximately 30 minutes to 4 hours is preferable. The preheating process may also be performed under reduced pressure.

[0049] Examples of the abrasive grains 12 include particles made of the above-mentioned minerals, metal or semimetal carbides, oxides, nitrides, etc. Diamond and CBN are preferably used, for example. Examples of the glass flux include compounds containing boron (B), lead (Pb), fluorine (F), alkali metal elements, alkaline earth metal elements, etc. Preferred examples include boric acid powder, Ca resinate, borax, and soluble compounds containing the above elements.

[0050] The liquid medium may be, for example, a solvent that dissolves the glass flux 14 or a dispersion medium that disperses the glass flux 14. The liquid medium may be aqueous or organic. Examples of aqueous liquid media include water and water-based mixtures (e.g., a water and ethanol mixture). Examples of organic liquid media include alcohols such as sclareol, citronellol, phytol, geranylinalool, texanol, benzyl alcohol, ethanol, phenoxyethanol, 1-phenoxy-2-propanol, terpineol, dihydroterpineol, isoborneol, butylcarbitol, and diethylene glycol; esters such as terpineol acetate, dihydroterpineol acetate, isobornyl acetate, carbitol acetate, and diethylene glycol monobutyl ether acetate; and mineral spirits. Among these, alcohol-based and ester-based liquid media are preferred. The liquid medium may be used alone or in combination of two or more.

[0051] Preferably, the glass flux 14 is dissolved in a solvent in the first mixing process. In another preferred embodiment, the glass flux 14 is dispersed in a dispersion medium in the first mixing process. This allows the glass flux 14 to adhere to the surfaces of the abrasive grains 12 with little bias.

[0052] Preferably, step (A) further includes a process of firing the abrasive grains 12 to which the glass flux 14 is attached. The firing process in step (A) (hereinafter also referred to as the "first firing process") is not particularly limited as long as it is performed under conditions that stabilize the glass flux 14 attached to the surfaces of the abrasive grains 12. The first firing process is preferably performed in an oxidizing atmosphere (e.g., in air). The maximum firing temperature in step (A) varies depending on the type of abrasive grains 12 and glass flux 14 and is not generally specified. However, it is preferably, for example, 150°C to 1000°C, and may be 200°C to 900°C, or 300°C to 800°C. When diamond is used as the abrasive grains 12, a maximum firing temperature that is too high may oxidize the diamond, so it is preferably set to, for example, 700°C or less. The firing time is not particularly limited, but it is preferably, for example, 30 minutes to 4 hours.

[0053] In step (B), the mixture containing the abrasive and the vitrified bond 20 is fired. Specifically, step (B) may include a mixing process (hereinafter also referred to as "second mixing process") in which the abrasive, the vitrified bond 20, and the binder are mixed until they become a paste, a process in which the mixture is molded, and a firing process in which the molded body is fired. The stirring and mixing method in the second mixing process is not particularly limited, and can be carried out using various conventionally known stirring and mixing devices as described above. The molding process is not particularly limited, and can be performed by, for example, press molding.

[0054] Any glass powder having the above-described composition after firing can be used as the vitrified bond 20. From the viewpoint of adhesion for favorably bonding the abrasive grains 12, glass powders containing Bi2O3-ZnO-B2O3-SiO2 glass, SiO2-B2O3-R2O-RO glass, etc. can be preferably used.

[0055] The binder functions to bind the abrasive grains 12 together and to the vitrified bond 20 before firing. This improves shape stability until firing. However, the binder can become an unnecessary component after the abrasive grains 12 and the vitrified bond 20 are integrated by firing. Therefore, it is preferable that the binder be a component that is burned away by firing and does not remain in the fired grinding wheel 100. As such a binder, any organic compound with binder function can be used without particular limitation. For example, specifically, binder resins based on acrylic resins such as polybutyl methacrylate, polymethyl methacrylate, and polyethyl methacrylate; cellulose-based polymers such as ethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose; epoxy resins, phenolic resins, alkyd resins, vinyl resins such as polyvinyl alcohol and polyvinyl butyral; and rosin-based resins such as rosin and maleated rosin are preferably used. Note that one type of binder may be used alone, or two or more types may be used in combination. It should be noted that various additives other than those described above may be added to the grinding wheel 100 without departing from the scope of the present invention. Suitable examples of such additives include pore-forming agents, surfactants, antifoaming agents, antioxidants, dispersants, and rheology modifiers.

[0056] Although not particularly limited, the ratio of the weight Y of the glass flux contained in the abrasive to the weight X of the vitrified bond (weight Y / weight X) is preferably 0.1 or less. This makes it possible to improve the fluidity of the vitrified bond 20 near the surface of the abrasive grains 12 without changing the bulk properties of the vitrified bond 20, even when an abrasive containing a glass flux 14 is used. The ratio of the weight Y of the glass flux contained in the abrasive to the weight X of the vitrified bond (weight Y / weight X) is preferably 0.1 or less, and may be 0.05 or less, 0.02 or less, 0.01 or less, or 0.005 or less. The lower limit is not particularly limited, and may be, for example, 0.001 or more.

[0057] Step (B) may include a process of drying the mixture containing the abrasive and the vitrified bond 20 after the second mixing process. The drying process is not particularly limited, but may be performed, for example, at a temperature of about 50°C to 120°C for about 1 hour to 6 hours. For drying, a conventionally known drying method such as forced air drying, heat drying, or vacuum drying can be used. Then, it is preferable to carry out a molding process after the drying process.

[0058] In step (B), a firing process (hereinafter also referred to as a "second firing process") is preferably performed under conditions such that the glass flux 14 contained in the abrasive prepared in step (A) does not remain in the prepared state. This more preferably enhances the fluidity of the vitrified bond 20 near the surface of the abrasive grains 12. Furthermore, a decrease in strength due to the glass flux 14 remaining in the manufactured grinding wheel 100 is suppressed. Specifically, step (B) is preferably performed under conditions such that the glass flux prepared in step (A) is suitably oxidized by firing so that the composition of the glass flux in step (B) differs from that of the glass flux in step (A). Furthermore, step (B) is preferably performed under conditions such that the glass flux prepared in step (A) is suitably melted by firing so that the shape of the glass flux in step (B) differs from that of the glass flux in step (A).

[0059] In step (B), the mixture of the abrasive and the vitrified bond 20 is preferably fired at a temperature higher than the softening point of the vitrified bond 20. This causes the glass flux 14 contained in the abrasive to react with the vitrified bond 20, promoting melting and softening of the vitrified bond 20 near the surface of the abrasive grains 12. Therefore, even when firing at a relatively low temperature (e.g., 700°C or less) or when abrasive grains 12 with low wettability with the vitrified bond 20 are used, the abrasive grain retention force of the fired grinding wheel 100 can be improved. Here, when a material that easily oxidizes (e.g., diamond) is used as the abrasive grains 12, the firing temperature must be set relatively low (typically 800°C or less in air, e.g., 700°C or less). Diamond is generally known to have poor wettability with the vitrified bond 20. In the technology disclosed herein, the glass flux 14 adheres to the surface of the diamond abrasive grains 12, thereby effectively exerting the above-mentioned effect, and therefore a grinding wheel 100 with high strength can be realized even when fired at a relatively low temperature.

[0060] The firing treatment (second firing treatment) in step (B) is preferably carried out in an oxidizing atmosphere (for example, in air, etc.). The maximum firing temperature in the second firing treatment is not generally specified because it differs depending on the type of abrasive and vitrified bond 20, but is required to be at least equal to or higher than the softening point of the vitrified bond 20. For example, the maximum firing temperature in firing in step (B) is preferably 300°C or higher and 1000°C or lower, and may be 400°C or higher and 800°C or lower, or may be 450°C or higher and 700°C or lower. The firing time is not particularly limited, but it is recommended to fire for, for example, about 1 hour to 10 hours.

[0061] After step (B), the vitrified bond 20 is solidified by cooling to room temperature, and the grinding wheel 100 in which the plurality of abrasive grains 12 are bonded together can be manufactured.

[0062] The vitrified grinding wheel disclosed herein can be used to grind workpieces of various materials and shapes. Examples of the material of the workpiece include metals or semimetals, such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, and stainless steel, or alloys thereof; glass materials, such as quartz glass, aluminosilicate glass, and glassy carbon; ceramic materials, such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; and semiconductor substrate materials, such as silicon carbide, gallium nitride, and gallium arsenide. The workpiece may also be composed of a combination of these materials. In particular, the vitrified grinding wheel disclosed herein is suitable for grinding workpieces made of metals or semiconductor materials. Because the vitrified grinding wheel disclosed herein has high abrasive grain retention and improved durability, it can be used effectively for high-load grinding, such as ultra-high-speed grinding.

[0063] As described above, specific aspects of the technology disclosed herein include those described in the following sections.

[0064] Item 1: A method for manufacturing a vitrified grinding wheel, comprising: a step (A) of preparing an abrasive having a glass flux attached to the surface of the abrasive grain; and a step (B) of firing a mixture containing the abrasive and a vitrified bond, wherein the step (B) causes a reaction between the glass flux and the vitrified bond, thereby promoting melting or softening of the vitrified bond in the vicinity of the surface of the abrasive grain.

[0065] Item 2: In the step (B), the firing is carried out under conditions such that the glass flux contained in the abrasive prepared in the step (A) does not remain in the composition and shape as prepared. The manufacturing method according to item 1.

[0066] Item 3: The manufacturing method according to Item 1 or 2, wherein the step (A) includes a mixing treatment of mixing the abrasive grains with the glass flux or a material containing the glass flux.

[0067] Item 4: The manufacturing method according to any one of Items 1 to 3, wherein the step (A) includes a firing treatment of firing the abrasive material having the glass flux attached to the surface of the abrasive grains.

[0068] Item 5: The method according to Item 4, wherein the firing treatment in step (A) is carried out at a temperature of 150°C or higher and 1000°C or lower.

[0069] Item 6: The method according to any one of Items 1 to 5, wherein the firing in step (B) is carried out at a temperature of 300°C or higher and 1000°C or lower.

[0070] Item 7: The manufacturing method according to any one of Items 1 to 6, wherein in the step (B), the ratio (Y / X) of the weight Y of the glass flux to the weight X of the vitrified bond is 0.1 or less.

[0071] Item 8: An abrasive used in the manufacture of a vitrified grinding wheel, comprising abrasive grains and a glass flux attached to the surface of the abrasive grains, wherein the amount of glass flux attached in volume conversion per unit surface area of the abrasive grains is 0.2 mm 3 / m 2 More than 50mm 3 / m 2 Below is the abrasive.

[0072] Item 9: The abrasive according to Item 8, wherein the glass flux is a compound containing at least one selected from the group consisting of boron, lead, fluorine, alkali metal elements, and alkaline earth metal elements.

[0073] Item 10: The abrasive material according to Item 8 or 9, wherein the abrasive grains are either diamond or cubic boron nitride.

[0074] Item 11: The abrasive material according to any one of Items 8 to 10, wherein the glass flux is partially attached to the surface of the abrasive grains.

[0075] Item 12: BET specific surface area A (m 2 / g) to the BET specific surface area B (m 212. The abrasive material according to any one of items 8 to 11, wherein the ratio (B / A) of the surface roughness of the abrasive material to the surface roughness of the abrasive material (B / A) is 1.3 or less.

[0076] Item 13: The abrasive according to any one of Items 8 to 12, wherein the content of the glass flux is 10 wt % or less when the entire abrasive is taken as 100 wt %.

[0077] Item 14: The amount of glass flux attached per unit area of the abrasive grain (mg / m 2 ) is 0.02 mg / m 2 More than 50mg / m 2 Item 14. The abrasive material according to any one of items 8 to 13, which is:

[0078] Item 15: A vitrified grinding wheel including a plurality of abrasive grains and a vitrified bond that bonds the plurality of abrasive grains to one another, wherein the concentration of a glass flux component at a position P1 where the abrasive grains and the vitrified bond contact each other is higher than the concentration of the glass flux component at a position P2 where the abrasive grains and the vitrified bond do not contact each other, and wherein the glass flux component is at least one of boron, lead, fluorine, an alkali metal element, and an alkaline earth metal element.

[0079] Item 16: The vitrified grinding wheel according to Item 15, wherein the softening point of the vitrified bond at a position P1 where the abrasive grains and the vitrified bond contact each other is lower than the softening point of the vitrified bond at a position P2 where the abrasive grains and the vitrified bond do not contact each other.

[0080] <Test example> Hereinafter, examples of the technology disclosed herein will be described, but it is not intended that the technology disclosed herein be limited to those shown in these examples.

[0081] <First test> In this test, three types of abrasive grains, A to C, were prepared, and the grinding strength of the grinding wheels using each abrasive grain was evaluated.

[0082] 1. Preparing the abrasive (1) Abrasive material A First, 20 g of diamond (FRM4-6, manufactured by Global Diamond Co., Ltd.), 0.094 g of boric acid (B(OH)3) (0.053 g in terms of B2O3), and 25 g of ethanol were prepared. After dissolving the boric acid in ethanol, the diamond was added and stirred. A mixture was then obtained by dispersion using an ultrasonic cleaner. The mixture was dropped onto a glass plate placed on a hot plate at 80°C and allowed to dry. The glass plate was then placed in a vacuum oven at 80°C and dried in the vacuum oven for 1 hour. The dried product was then crushed in a mortar. The mixture was then fired in an air atmosphere at 600°C, with a heating rate of 10°C / min and a heat treatment time of 30 minutes. This oxidized the boric acid, resulting in a fired product with boron oxide (B2O3) attached to the diamond (abrasive grain) surface. The resulting fired product was crushed in a mortar to prepare Abrasive A.

[0083] (2) Abrasive material B The diamond (FRM4-6, manufactured by Global Diamond Co., Ltd.) used in Abrasive A was used as Abrasive B without any glass flux attached.

[0084] (3) Abrasive material C 20 g of the diamond (FRM4-6, manufactured by Global Diamond Co., Ltd.) used in Abrasive A, 0.88 g of Si resinate (SiO2 content: 7.15 wt%) (0.063 g in SiO2 equivalent), and 25 g of ethanol were prepared. After dissolving boric acid in ethanol, the diamond was added and stirred. A dispersion process was then performed using an ultrasonic cleaner to obtain a mixture. The mixture was dropped onto a glass plate placed on a hot plate at 80°C and allowed to dry. The glass plate was then placed in a vacuum oven at 80°C and dried in the vacuum oven for 1 hour. The dried product was then crushed in a mortar. The mixture was then heat-treated in air at 600°C, with a heating rate of 10°C / min and a heat treatment time of 30 minutes. This resulted in a fired product with silicon oxide attached to the diamond (abrasive grain) surface. The fired product was then crushed in a mortar to prepare Abrasive C.

[0085] 2. Evaluation of abrasives (1) BET measurement Each abrasive was tested using a specific surface area measuring device (model: BELSORP-max) manufactured by Microtrac-Bell, and the N2 adsorption isotherm at -196°C was measured to determine the BET specific surface area based on the BET multipoint method. 2 / g), the BET specific surface area of abrasive B is used, and the BET specific surface area A (m 2 / g) of the BET specific surface area B(m 2 The ratio (B / A) of the total weight of the particles to the total weight of the particles (g) was calculated. The results are shown in Table 1.

[0086] (2) Calculation of content, etc. Based on the mixing ratio (weight ratio) of the constituent materials of each abrasive, the average thickness (nm) of the attached material and the content (wt%) of the attached material were calculated. In addition, the weight (g) and density of the constituent materials of each abrasive (diamond: 3.52 g / cm 3 , B2O3: 1.85g / cm 3 , SiO2: 2.2 g / cm 3 ) and the volumetric content (vol%) of the adhesive material was calculated using the BET specific surface area and the content value measured above. In addition, the adhesion amount per unit surface area of abrasive grains and the volumetric adhesion amount per unit surface area of abrasive grains were calculated using the BET specific surface area and the content value measured above. The results are shown in Table 1.

[0087] 3. Preparation of grinding wheel test specimens (1) Example 1 8.12 g of the prepared abrasive A, 7.89 g of Bi2O3-ZnO-B2O3-SiO2 glass powder (TMX-501F, manufactured by TOMATEC Corporation) as vitrified bond raw material powder, 1.97 g of pore former (Technopolymer, MB30X-8Y, manufactured by Sekisui Plastics Co., Ltd.), and 3.03 g of binder (Orikox, #2435E, manufactured by Kyoeisha Scientific Co., Ltd.) were prepared. Abrasive A, glass frit, pore former, and binder were mixed using a mixer (Awatori Rentaro, AR-550L-2) until a paste was formed. The mixture was dried at 100°C for 4 hours and crushed in a mortar to obtain grinding stone clay. 3.0 g of this grinding stone clay was press-molded to a length of 55 mm, width d of 6.5 mm, and thickness h of 4 mm, to prepare five compacts. These compacts were fired in an air atmosphere under the following conditions: the temperature was raised to 400°C over 5 hours, held at 400°C for 2 hours, raised to 570°C over 1 hour and 40 minutes, and held at 570°C for 2 hours. The fired compacts were cooled over 4 hours or more to produce five grinding wheel test pieces according to Example 1.

[0088] (2) Example 2 Five grindstone test pieces according to Example 2 were prepared in the same manner as in Example 1, except that abrasive material B was used instead of abrasive material A.

[0089] (3) Example 3 Five grindstone test pieces according to Example 3 were prepared in the same manner as in Example 1, except that abrasive material C was used instead of abrasive material A.

[0090] 4. Evaluation of Grinding Wheel Test Pieces (1) Measurement of three-point bending strength and calculation of three-point bending modulus A three-point bending strength test was performed on the grinding wheel test pieces (five pieces each) of Examples 1 to 3 using an EZ-test made by Shimadzu Corporation, and the arithmetic mean value was calculated. In this test, the distance L between the supports of the support fixture fixing the grinding wheel test pieces was set to 30 mm. The pressure rate during the test was set to 0.5 mm / min. The results are shown in Table 1. The three-point bending modulus is calculated using the following formula: Three-point bending modulus = (L 3 / 4dh 3) × (ΔF / Δs); where L is the distance between supports (30 mm), d is the width of the grinding wheel test piece (6.5 mm), h is the thickness of the grinding wheel test piece (4 mm), ΔF is the change in bending load of the test piece at 25% to 50% of the yield load, and Δs is the change in deflection of the test piece at 25% to 50% of the yield load. In addition, the three-point bending elastic modulus was calculated for five pieces for each example, and the arithmetic average was calculated. The results are shown in Table 1.

[0091] (2) Microscopic observation of grinding wheel test piece After the three-point bending strength test, the cross sections of the grinding wheel test pieces of Examples 1 to 3 were observed under a microscope. Such microscopic observation was carried out using a field emission scanning electron microscope (FE-SEM) manufactured by Hitachi High-Technologies Corporation. FE-SEM photographs of Examples 1 to 3 taken at this time are shown in Figures 3 to 5. Note that the white parts in Figures 3 to 5 represent the vitrified bond, and the black parts represent the abrasive grains.

[0092] [Table 1]

[0093] As shown in Table 1, the three-point bending strength and three-point bending modulus of the grinding wheel test piece in Example 1 are both improved compared to Examples 2 and 3. Therefore, it can be seen that the grinding wheel strength of the grinding wheel can be improved by using an abrasive material in which a glass flux adheres to the surface of the abrasive grains as the grinding wheel material.

[0094] As shown in Figures 3 to 5, in Example 1, the amount of exposed abrasive grains is smaller than in Examples 2 and 3, and wetting between the abrasive grains and the vitrified bond is better. This is presumably because boron oxide functions as a glass flux during the heat treatment used to produce the grinding wheel, increasing the fluidity of the vitrified bond near the abrasive grains. This is presumably why the abrasive grain retention force of Example 1 is improved after heat treatment.

[0095] Furthermore, the BET specific surface area of Example 1, which had boron oxide attached, was equivalent to that of Example 2, which had no attached material, indicating that the structure of the attached boron oxide was not particulate. This is presumably because the boric acid was calcined during the heat treatment used to produce the abrasive, and the resulting boron oxide adhered to the abrasive grain surface in an amorphous form. On the other hand, the BET specific surface area of Example 3, which had silicon oxide attached, was larger than that of Example 2, which had no attached material, indicating that the attached silicon oxide was particulate. This is presumably because the heat treatment used to produce the abrasive caused the silicon oxide to adhere to the abrasive grain surface in a particulate form. Furthermore, as shown in Table 1, despite the presence of silicon oxide attached, Example 3 had the same three-point bending modulus of the grinding wheel test piece as Example 2, which had no attached material, and also had a lower three-point bending strength than Example 2. This is presumably because silicon oxide generally does not function as a glass flux, and therefore does not improve the wetting between the abrasive grains and the vitrified bond, thereby not improving the abrasive grain retention.

[0096] <Second test> In this test, six types of abrasives D to I were prepared by varying the type and amount of glass flux, and the strength of the grinding wheels using each abrasive was evaluated.

[0097] 1.Preparing the abrasive (1) Abrasive material D First, 20 g of pseudo-polycrystalline diamond (FRM-DN-4-6, manufactured by Global Diamond Co., Ltd.), 0.094 g of boric acid (0.053 g in terms of B2O3), and 25 g of ethanol were prepared. After dissolving the boric acid in ethanol, the diamond was added and stirred. A mixture was then obtained by dispersion using an ultrasonic cleaner. The mixture was dropped onto a glass plate placed on a hot plate at 80°C and allowed to dry. The glass plate was then placed in a vacuum oven at 80°C and dried in the vacuum oven for 1 hour. The dried product was then crushed in a mortar. The mixture was then fired in an air atmosphere at 600°C, with a heating rate of 10°C / min and a heat treatment time of 30 minutes. This oxidized the boric acid, resulting in a fired product with boron oxide attached to the diamond (abrasive grain) surface. The resulting fired product was crushed in a mortar to prepare abrasive D.

[0098] (2) Abrasive material E Abrasive E was prepared in the same manner as Abrasive D, except that the amount of boric acid was 10 times greater (ie, 0.94 g).

[0099] (3) Abrasive material F Abrasive F was prepared in the same manner as Abrasive D, except that 1.05 g (0.095 g in terms of CaO) of Ca resinate (content in terms of CaO: 9.08 wt%) was prepared instead of boric acid.

[0100] (4) Abrasive material G Instead of boric acid, 0.15 g of borax (Na2B4O7) was prepared. Also, instead of ethanol, 25 g of pure water was prepared. Abrasive G was prepared in the same manner as Abrasive D, except for these changes.

[0101] (5) Abrasive material H The diamond (FRM-DN 4-6, manufactured by Global Diamond Co., Ltd.) used in Abrasive D was used as Abrasive H without any glass flux attached.

[0102] (4) Abrasive material I Abrasive I was prepared in the same manner as Abrasive D, except that the amount of boric acid was 4.67 g and the amount of ethanol was 50 g.

[0103] 2. Evaluation of abrasives (1) BET measurement Each abrasive was tested using a specific surface area measuring device (model: BELSORP-max) manufactured by Microtrac-Bell, and the N2 adsorption isotherm at -196°C was measured to determine the BET specific surface area based on the BET multipoint method. 2 / g), the BET specific surface area of the abrasive grains is used as the BET specific surface area A (m 2 / g) of the BET specific surface area B(m 2 The ratio (B / A) of the total weight of the particles to the total weight of the particles (g) was calculated. The results are shown in Table 2.

[0104] (2) Calculation of content, etc. Based on the mixing ratio (weight ratio) of the constituent materials of each abrasive, the average thickness (nm) of the adhesive (glass flux) and the content (wt%) of the glass flux were calculated. In addition, the weight (g) and density (wt%) of the constituent materials of each abrasive were calculated. 3 , B2O3: 1.85g / cm 3 , CaO: 3.34 g / cm 3 , Na2B4O7: 1.72 g / cm 3 ) and the volumetric content (vol%) of the glass flux was calculated using the BET specific surface area and the content value measured above. In addition, the adhesion amount per unit surface area of the abrasive grains and the volumetric adhesion amount per unit surface area of the abrasive grains were calculated using the BET specific surface area and the content value measured above. The results are shown in Table 2.

[0105] 3. Preparation of grinding wheel test specimens (1) Example 11 8.12 g of the prepared abrasive D, 7.89 g of Bi2O3-ZnO-B2O3-SiO2 glass powder (TMX-501F, manufactured by TOMATEC Corporation) as vitrified bond raw material powder, 1.97 g of pore former (Technopolymer, MB30X-8Y, manufactured by Sekisui Plastics Co., Ltd.), and 3.03 g of binder (Orikox, #2435E, manufactured by Kyoeisha Scientific Co., Ltd.) were prepared. Abrasive D, glass frit, pore former, and binder were mixed using a mixer (Awatori Rentaro, AR-550L-2) until a paste was formed. The mixture was dried at 100°C for 4 hours and crushed in a mortar to obtain grinding stone clay. 3.0 g of this grinding stone clay was press-molded to a length of 55 mm, width d of 6.5 mm, and thickness h of 4 mm, to prepare five compacts. These compacts were fired in an air atmosphere under the following conditions: the temperature was raised to 400°C over 5 hours, held at 400°C for 2 hours, raised to 570°C over 1 hour and 40 minutes, and held at 570°C for 2 hours. The fired compacts were cooled over 4 hours or more to produce five grinding wheel test pieces according to Example 11.

[0106] (2) Examples 12 to 16 Five grindstone test pieces for each of Examples 12 to 16 were prepared in the same manner as in Example 11, except that abrasive grains E to I were used instead of abrasive material D, respectively.

[0107] 4. Evaluation of Grinding Wheel Test Pieces A three-point bending strength test was performed on the grinding wheel test pieces (five pieces each) of Examples 11 to 16 using an EZ-test made by Shimadzu Corporation, and the arithmetic mean value was calculated. In this test, the distance L between the supports of the support fixture fixing the grinding wheel test pieces was set to 30 mm. The pressure rate during the test was set to 0.5 mm / min. The results are shown in Table 2. The three-point bending modulus is calculated using the following formula: Three-point bending modulus = (L 3 / 4dh 3) × (ΔF / Δs); where L is the distance between supports (30 mm), d is the width of the grinding wheel test piece (6.5 mm), h is the thickness of the grinding wheel test piece (4 mm), ΔF is the change in bending load of the test piece at 25% to 50% of the yield load, and Δs is the change in deflection of the test piece at 25% to 50% of the yield load. In addition, the three-point bending elastic modulus was calculated for five pieces for each example, and the arithmetic average was calculated. The results are shown in Table 2. Both the three-point bending strength and the three-point bending modulus are values that indicate the strength of the grinding wheel test piece, and if either one is improved, it can be said that the strength of the grinding wheel test piece is improved.

[0108] [Table 2]

[0109] As shown in Table 2, in Examples 11 to 14, at least one of the three-point bending strength and three-point bending modulus of elasticity of the grinding wheel test pieces is improved compared to Example 15. Therefore, it can be seen that regardless of the type of glass flux, the grinding wheel strength of the grinding wheel can be improved by using, as the grinding wheel material, an abrasive material having a glass flux adhered to the surface of the abrasive grains.

[0110] On the other hand, in Example 16, both the three-point bending strength and three-point bending modulus of the grinding wheel test piece are lower than those in Example 15. It is clear that if the volumetric amount of glass flux attached per unit surface area of the abrasive grains is too large, it will reduce the strength of the grinding wheel. Therefore, the volumetric amount of glass flux attached per unit surface area of the abrasive grains is 0.2 mm 3 / m 2 More than 50mm 3 / m 2 It is preferable that:

[0111] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0112] 12 abrasive grains 14 Glass flux 20 Vitrified Bond 30 void 100 whetstones

Claims

1. A method for manufacturing a vitrified grinding wheel, comprising: A step (A) of preparing an abrasive material having a glass flux attached to the surface of abrasive grains; A step (B) of firing the mixture containing the abrasive and the vitrified bond; Including, In this method for manufacturing a vitrified grinding wheel, the glass flux is a flux component that promotes melting and softening of the vitrified bond.

2. 2. The manufacturing method according to claim 1, wherein the step (B) lowers the softening point (°C) of the vitrified bond in the vicinity of the surface of the abrasive grains by using the glass flux.

3. The manufacturing method according to claim 1 or 2, wherein the step (A) includes a mixing treatment of mixing the abrasive grains with the glass flux or a material containing the glass flux.

4. 3. The manufacturing method according to claim 1, wherein the step (A) includes a firing treatment for firing the abrasive material having the glass flux adhered to the surface of the abrasive grains.

5. The method according to claim 4, wherein the firing treatment in step (A) is carried out at a temperature of 150°C or higher and 1000°C or lower.

6. The method according to claim 1 or 2, wherein the firing in step (B) is carried out at a temperature of 300°C or higher and 1000°C or lower.

7. 3. The manufacturing method according to claim 1, wherein in the step (B), a ratio (Y / X) of a weight Y of the glass flux to a weight X of the vitrified bond is 0.1 or less.

8. A vitrified grinding wheel comprising a plurality of abrasive grains and a vitrified bond that bonds the plurality of abrasive grains to each other, A vitrified grinding wheel, wherein the softening point (°C) of the vitrified bond at a position P1 where the abrasive grains and the vitrified bond contact each other is lower than the softening point (°C) of the vitrified bond at a position P2 where the abrasive grains and the vitrified bond do not contact each other.

9. An abrasive used in the vitrified grinding wheel according to claim 8, The abrasive grains; a glass flux adhered to the surface of the abrasive grain; Including, The glass flux is a flux component that promotes melting and softening of the vitrified bond.

10. The abrasive material according to claim 9, wherein the amount of glass flux attached per unit surface area of ​​the abrasive grains converted into a volume is 0.2 mm 3 / m 2 or more and 50 mm 3 / m 2 or less.

11. The abrasive material described in claim 9, wherein the abrasive grains are either diamond or cubic boron nitride.

12. An abrasive material as described in claim 9, wherein the glass flux is partially adhered to the surface of the abrasive grain.

13. An abrasive material as described in claim 9, wherein the ratio (B / A) of the BET specific surface area B (m 2 / g) of the abrasive grains having the glass flux adhered to their surfaces to the BET specific surface area A (m 2 / g) of the abrasive grains is 1.3 or less.

14. An abrasive as described in claim 9, wherein the content of the glass flux is 10 wt% or less when the entire abrasive is taken as 100 wt%.

15. The abrasive material according to claim 9, wherein the amount of glass flux attached per unit area of ​​the abrasive grains (mg / m 2 ) is 0.02 mg / m 2 or more and 50 mg / m 2 or less.

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