Method for manufacturing vitrified grinding wheel, abrasive used therefor, and vitrified grinding wheel

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 used therefor, and a vitrified grinding wheel.

Background Art

[0002] As a grinding tool for finishing the surface or cross-section of a metal material or the like, a grinding wheel in which abrasive grains are bonded by a binder is used. As such grinding wheels, for example, depending on the type of binder, vitrified grinding wheels, resinoid grinding wheels, metal grinding wheels, etc. are known.

[0003] In the above-described grinding wheels, depending on the combination of abrasive grains and binder, the wettability and adhesion between the abrasive grains and the binder tend to be low, and sufficient grinding wheel strength may not be obtained, or the abrasive grain holding force may become insufficient. In contrast, it has been conventionally proposed to coat the abrasive grains with a material different from the abrasive grains to improve the grinding wheel strength and the abrasive grain holding force. For example, in Patent Document 1, it is disclosed 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, whereby the abrasive grain holding force is improved. In Patent Document 2, it is disclosed that by coating the surface of superabrasives such as diamond and CBN with particulate oxides, the abrasive grain holding force is improved by an anchor effect. Further, in Patent Document 3, it is disclosed that the surface of superabrasives is coated with a ceramic other than an oxide to improve the abrasive grain holding force of the grinding wheel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the method described in Patent Document 2 above is used, irregularities are generated on the surface of the abrasive grains due to the coating, and for example, there is a risk that the fluidity of the abrasive grains will decrease when the abrasive grains and the binder are mixed. Further, for example, when the surface of the abrasive grains is coated with a layer of aluminum oxide or silicon oxide as described in Patent Document 1, there is a possibility of increasing the softening point of the binder and promoting the crystallization of the binder, which may affect the properties of the abrasive grains and cause a decrease in the abrasive grain holding force. Further, as described in Patent Document 3, for CBN, the wettability between the abrasive grains and the vitrified bond can be improved by the reaction with the vitrified bond, but there is a problem that the abrasive grains wear down. Furthermore, Patent Document 3 describes that when boron oxide is generated between the abrasive grains and the vitrified bond by the reaction between them, the strength of boron oxide is quite low and the adhesion to the abrasive grains is also weak, so that the abrasive grain holding force becomes low. Therefore, there is still room for improvement from the viewpoint of improving the grinding wheel strength and the abrasive grain holding force.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for manufacturing a vitrified grinding wheel for improving the grinding wheel strength, an abrasive material used therefor, and a vitrified grinding wheel having improved grinding wheel strength.

Means for Solving the Problems

[0007] The method for manufacturing a vitrified grinding wheel disclosed herein includes a step (A) of preparing an abrasive material having a glass flux adhered to the surface of abrasive grains, and a step (B) of firing a mixture containing the abrasive material and a vitrified bond. The step (B) is characterized by reacting the glass flux and the vitrified bond to promote melting or softening of the vitrified bond in the vicinity of 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 production of a vitrified grinding wheel, when firing a mixture of the abrasive material and the vitrified bond, the melting and softening of the vitrified bond are promoted in the vicinity of the abrasive grains by the glass flux. As a result, after the production of the grinding wheel, the abrasive grains are suitably held by the vitrified bond, so that a vitrified grinding wheel with high grinding wheel strength can be provided.

[0009] In a preferred embodiment of the manufacturing method disclosed herein, in the above step (B), the firing is carried out under firing conditions such that the glass flux contained in the abrasive material prepared in the above step (A) does not remain in its prepared composition and shape. According to such a configuration, the fluidity of the vitrified bond in the vicinity of the surface of the abrasive grains can be more suitably increased, and a decrease in strength due to the remaining glass flux in the grinding wheel 100 after production is suppressed, and a grinding wheel with high strength can be provided.

[0010] In a preferred embodiment of the manufacturing method disclosed herein, in the above step (A), a mixing process of mixing the abrasive grains and the glass flux or a material containing the glass flux is included. According to such a configuration, the glass flux can be suitably attached to the surface of the abrasive grains.

[0011] In a preferred embodiment of the manufacturing method disclosed herein, in the above step (A), a firing process of firing the abrasive material with the glass flux attached to the surface of the abrasive grains is included. Further, in a preferred embodiment of such a firing process, firing is carried out at a temperature of 150°C or higher and 1000°C or lower. According to such a configuration, the glass flux attached to the surface of the abrasive grains can be stabilized.

[0012] In a preferred embodiment of the manufacturing method disclosed herein, in the above step (B), firing is carried out at a temperature of 300°C or higher and 1000°C or lower. According to such a configuration, a vitrified grinding wheel with high grinding wheel strength can be provided without affecting the properties of the abrasive grains.

[0013] In a preferred embodiment of the manufacturing method disclosed herein, in the above step (B), the ratio (Y / X) of the weight Y of the glass frit to the weight X of the vitrified bond is 0.1 or less. According to such a configuration, wetting with the vitrified bond can be improved without affecting the grinding function of the abrasive grains.

[0014] Further, according to the technology disclosed herein, an abrasive material used for manufacturing a vitrified grinding wheel is provided. The abrasive material disclosed herein includes abrasive grains and a glass frit attached to the surface of the abrasive grains. The amount of the glass frit attached in terms of volume per unit surface area of the abrasive grains is 0.2 mm 3 / m 2 or more and 50 mm 3 / m 2 or less. According to such a configuration, when manufacturing a vitrified grinding wheel, the fluidity of the vitrified bond in the vicinity of the surface of the abrasive grains is improved by the glass frit. As a result, regardless of the properties of the abrasive grains, a network between the abrasive grains and the vitrified bond can be preferably formed, and a grinding wheel with high grinding wheel strength can be provided.

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

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

[0017] In a preferred embodiment of the abrasive material disclosed herein, the glass frit is partially adhered to the surface of the abrasive grains. According to such a configuration, the grinding function of the abrasive grains can be preferably exhibited.

[0018] In a preferred embodiment of the abrasive material disclosed herein, the BET specific surface area B (m 2 / g) of the abrasive grains with the glass frit adhered to the surface thereof with respect to the BET specific surface area A (m 2 / g) of the abrasive grains is 1.3 or less. According to such a configuration, while the abrasive material and the vitrified bond are preferably mixed, it is possible to easily melt and soften the vitrified bond in the vicinity of the surface of the abrasive grains.

[0019] In a preferred embodiment of the abrasive material disclosed herein, the amount of the glass frit adhered 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. In another preferred embodiment, the content of the glass frit is 10 wt% or less when the total amount of the abrasive material is 100 wt%. According to such a configuration, it is possible to improve the wetting between the abrasive grains and the vitrified bond without reducing the grinding function of the abrasive grains.

[0020] Also, according to the technology disclosed herein, a vitrified grinding wheel is provided. The vitrified grinding wheel disclosed herein includes a plurality of abrasive grains and a vitrified bond that binds the plurality of abrasive grains to each other. The concentration of the glass frit component at the position P1 where the abrasive grains and the vitrified bond are in contact is higher than the concentration of the glass frit component at the position P2 where the abrasive grains and the vitrified bond are not in contact. Here, the glass frit component is at least one of boron, lead, fluorine, alkali metal elements, and alkaline earth metal elements. According to such a configuration, the above-described effects are preferably exhibited, and a vitrified grinding wheel having 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 the position P1 where the abrasive grains and the vitrified bond are in contact is lower than the softening point of the vitrified bond at the position P2 where the abrasive grains and the vitrified bond are not in contact. According to such a configuration, the effect of including a plurality of abrasive grains with a glass frit attached to the surface is preferably exhibited, and a vitrified grinding wheel with high grinding wheel strength can be realized.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge 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 schematically drawn, and the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. In this specification, the "dispersion" refers to a mixture in which part or all of the solid content is dispersed in a liquid dispersion medium, including so-called "paste", "slurry", "ink", etc., regardless of the dispersion stability.

[0024] FIG. 1 schematically shows abrasive grains 12 with a glass frit 14 adhering to the surface. FIG. 2 schematically shows the structure of the grinding wheel 100. The abrasive material disclosed herein includes abrasive grains 12 and a glass frit 14 adhering to the surface of the abrasive grains 12. Further, the grinding wheel 100 disclosed herein includes a plurality of abrasive grains 12 and a vitrified bond 20 that binds the plurality of abrasive grains 12 to each other. The grinding wheel 100 can be produced by firing a mixture of the abrasive material and a binder (here, the vitrified bond 20) at an appropriate temperature. When manufacturing the grinding wheel 100, by using an abrasive material with a glass frit 14 adhering to the surface of the abrasive grains 12, the wetting between the abrasive grains 12 and the vitrified bond 20 can be enhanced. Further, when firing the mixture of the abrasive material and the vitrified bond 20, the glass frit 14 promotes the melting and softening of the vitrified bond 20, so that the vitrified bond 20 preferably flows in the vicinity of the abrasive grains 12, and the abrasive grain holding force of the fired grinding wheel 100 can be improved. Thereby, the strength of the grinding wheel 100 can be improved. Hereinafter, the abrasive material and the grinding wheel 100 disclosed herein will be described.

[0025] <Abrasive Material> The abrasive material contains abrasive grains 12. The abrasive grains 12 are the part that has the function of directly grinding the workpiece. The properties of the abrasive grains 12 are not particularly limited and may be appropriately selected according to the purpose of grinding, the usage mode, etc. The abrasive grains 12 can be determined in consideration of the physical properties such as the hardness of the workpiece. Examples of the abrasive grains 12 include particles made of minerals, carbides, oxides, nitrides of metals or semi-metals, etc. Specifically, diamond, cubic boron nitride (hereinafter also referred to as "CBN"), silica, alumina, ceria, etc. can be mentioned. Among them, diamond with a Knoop hardness of 4000 or more (Knoop hardness: about 7000 - 8000) and CBN (Knoop hardness: about 4700) can be preferably used. Note that the diamond may be natural diamond or artificial diamond. For example, artificial diamond is preferred because high-purity ones are easily obtained and various types of materials can be stably obtained as materials.

[0026] The shape of the abrasive grains 12 is not particularly limited and may be, for example, spherical, plate-shaped, irregular-shaped, etc. The size of the abrasive grains 12 can also be appropriately determined according to the purpose of use and the usage mode of the grindstone 100. For example, the average particle size of the abrasive grains 12 may be about 0.1 μm or more and 1000 μm or less, and it is preferably about 1 μm or more and 100 μm or less. Also, although not particularly limited, the average aspect ratio (major axis / minor axis ratio) 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. Incidentally, the average particle size of such 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 in the image obtained thereby, the equivalent circle diameter is determined by image analysis for a predetermined number (for example, 100 or more) of abrasive grains, and this arithmetic mean value can be taken as the average particle size of the abrasive grains. Further, the average aspect ratio can be determined as follows. In the above-obtained image, draw the smallest rectangle circumscribing each particle, and determine the length of the long side (major axis) and the length of the short side (minor axis) of the rectangle. Then, by calculating the value obtained by dividing the major axis by the minor axis (major axis / minor axis) and calculating the arithmetic mean value, the average aspect ratio of the abrasive grains can be determined.

[0027] Although not particularly limited, the BET specific surface area (m 2 / g) of the abrasive grains is preferably, for example, 0.01 m 2 / g or more and 100 m 2 / g or less, and may be 0.1 m 2 / g or more and 10 m 2 / g or less. In this specification, the "BET specific surface area of the abrasive grains" refers to the value obtained by analyzing the adsorption isotherm measured by the gas adsorption method using nitrogen (N2) gas as the adsorbate by the BET method.

[0028] The abrasive material disclosed herein contains a glass flux 14. Here, the glass flux (glass flux) is a flux component (flux component) that promotes the melting and softening of the vitrified bond 20. That is, the glass flux 14 is a component that exhibits the effect of increasing the softening fluidity of the vitrified bond 20. When manufacturing the grinding wheel 100, by using an abrasive material in which the glass flux 14 adheres to the surface of the abrasive grains 12, the vitrified bond 20 and the glass flux 14 react, and the vitrified bond 20 near the surface of the abrasive grains 12 is likely to melt and soften. As a result, the fluidity of the vitrified bond 20 is increased near the surface of the abrasive grains 12, and a network can be suitably formed. Therefore, the abrasive grain holding force is improved, and the grinding wheel strength of the grinding wheel 100 is improved.

[0029] Examples of such glass fluxes 14 include compounds containing boron (B), lead (Pb), fluorine (F), alkali metal elements, alkaline earth metal elements, and the like. 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 (B2O3), lithium oxide (Li2O), potassium oxide (K2O), 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 (Na2O3), potassium carbonate (K2CO3), and magnesium carbonate (MgCo3); nitrates such as sodium nitrate (NaNO3) and potassium nitrate (KNO3); compounds containing boron such as boric acid (B(OH)3) and borax (Na2B4O7); and the like. As the glass flux 14, one of the above-described glass flux components may be used alone, or two or more thereof may be mixed and used.

[0030] The BET specific surface area (m 2 / g) of the abrasive grains with the glass flux attached to the surface is, for example, preferably 0.01 m 2 / g or more and 100 m 2 / g or less, and may be 0.1 m 2 / g or more and 10 m 2 / g or less. In the abrasive material disclosed herein, the BET specific surface area B (m 2 / g) of the abrasive grains with the glass flux attached to the surface with respect to the BET specific surface area A (m 2The ratio (B / A) of (g) is preferably 1.3 or less, may be 1.2 or less, and may be 1.1 or less. That is, even if the glass frit 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 so much. According to such a configuration, when manufacturing the grinding wheel 100, while suitably mixing the abrasive material and the vitrified bond 20, in the firing stage of the mixture, the vitrified bond 20 can be easily melted and softened in the vicinity of the surface of the abrasive grains 12.

[0031] The content of the glass frit is preferably 10 wt% or less when the total amount of the abrasive material is 100 wt%. The content of the glass frit is more preferably 7 wt% or less, still more preferably 5 wt% or less, may be 3 wt% or less, may be 2 wt% or less, may be 1 wt% or less, and may be 0.8 wt% or less. Thereby, without reducing the function of grinding the workpiece, the wetting between the abrasive material and the vitrified bond 20 can be improved. Also, the abrasive grain holding force in the grinding wheel 100 can be improved without affecting the properties of the vitrified bond 20. On the other hand, when the content of the glass frit is too small, the above-described effects are not sufficiently exhibited. Therefore, the content of the glass frit is preferably, for example, 0.05 wt% or more, may be 0.1 wt% or more, and may be 0.5 wt% or more. The content of the glass frit in the total amount of the abrasive material can be determined, for example, by dissolving and removing the glass frit and quantifying the glass frit component contained in the solution by ICP emission analysis or the like.

[0032] The amount of glass frit adhesion per unit surface area of the abrasive grains (mg / m 2 ) is preferably 0.02 mg / m 2 or more from the viewpoint of sufficiently improving the fluidity of the vitrified bond 20 on the surface of the abrasive grains 12, may be 0.05 mg / m 2 or more, may be 0.1 mg / m 2 or more, and may be 1.5 mg / m 2It is more preferable that it is as described above. On the other hand, when the glass frit 14 adheres excessively to the surface of the abrasive grains 12, there is a possibility that the glass frit remains excessively in the grinding wheel 100 after manufacturing, which may reduce the strength and workability. From these viewpoints, the amount of glass frit adhesion per unit surface area of the abrasive grains is 50 mg / m 2 or less, preferably, and may be 30 mg / m 2 or less, more preferably, and may be 25 mg / m 2 or less, even more preferably, and may be 5 mg / m 2 or less, still more preferably, and may be 4 mg / m 2 or less, and most preferably, and may be 3 mg / m 2 or less. Note that the "amount of glass frit adhesion per unit surface area of the abrasive grains (mg / m 2 )" can be obtained from the content of the above glass frit and the BET specific surface area of the abrasive grains.

[0033] Also, the volume-converted amount of glass frit adhesion per unit surface area of the abrasive grains (mm 3 / m 2 ) is preferably 0.2 mm 3 / m 2 or more from the viewpoint of sufficiently improving the fluidity of the vitrified bond 20 on the surface of the abrasive grains 12, and may be 0.4 mm 3 / m 2 or more, and may be 0.7 mm 3 / m 2 or more, and may be 1 mm 3 / m 2 or more, and more preferably. On the other hand, when the glass frit 14 adheres excessively to the surface of the abrasive grains 12, there is a possibility that the glass frit remains excessively in the grinding wheel 100 after manufacturing, which may reduce the strength and workability. Therefore, the volume-converted amount of glass frit adhesion per unit surface area of the abrasive grains is preferably 50 mm 3 / m 2 or less, and may be 30 mm 3 / m 2 or less, and may be 20 mm 3 / m 2 or less, and may be 15 mm 3 / m 2It may be as follows, 14 mm 3 / m 2 It is more preferably as follows, 5 mm 3 / m 2 It may be as follows, 3 mm 3 / m 2 It is even more preferably as follows. Note that the "amount of vitrified flux adhered in terms of volume per unit surface area of abrasive grains (mm 3 / m 2 )" can be obtained from the content of the vitrified flux in terms of volume 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 vitrified flux 14 is fixed to the surface of the abrasive grains 12, for example. The shape and the existing form when the vitrified flux 14 adheres to the surface of the abrasive grains 12 are not particularly limited. For example, the shape of the vitrified flux 14 on the surface of the abrasive grains 12 may be particulate or film-like. When the vitrified flux 14 adheres in a particulate form, unevenness of about 0.05 μm to 300 μm may occur on the surface of the abrasive grains 12, so that the fluidity as a powder decreases. Therefore, from the viewpoints of mixing with the vitrified bond 20 and moldability, the shape when the vitrified flux 14 adheres to the surface of the abrasive grains 12 is preferably film-like. Further, the vitrified flux 14 may exist in the form of an amorphous structure on the surface of the abrasive grains 12. Alternatively, after an amorphous structure forms a skeleton, various metal elements (or metalloid elements) may exist in the skeleton in the form of oxides or in the form of cations (hereinafter, also referred to as "amorphous matrix structure"). Such a form of the vitrified flux 14 can be confirmed by microscopic observation.

[0035] The glass frit 14 may adhere to the entire surface of the abrasive grains 12, or may partially adhere to the surface of the abrasive grains 12. Preferably, the glass frit 14 may partially adhere to the surface of the abrasive grains 12. For example, as shown in FIG. 1, the glass frit 14 may be present in an island shape (i.e., scattered) on the surface of the abrasive grains 12. Thereby, in the manufactured grinding wheel 100, since the entire surface of the abrasive grains 12 not in contact with the vitrified bond 20 is not covered with the glass frit, the processing performance (e.g., cutting function) of the grinding wheel 100 is preferably exhibited. Note that the fact that the glass frit 14 is scattered on the surface of the abrasive grains 12 can be confirmed by a conventionally known method. For example, it can be confirmed by observing the surface and cross section of the abrasive grains using an electron microscope.

[0036] If the average thickness of the glass frit 14 is too thick, irregularities that cause an anchor effect may occur on the surface of the abrasive grains 12, and the fluidity of the abrasive may be inhibited. Therefore, the average thickness of the glass frit 14 is preferably, for example, 30 nm or less, may be 20 nm or less, more preferably 15 nm or less, and may be 10 nm or less. On the other hand, if it is too thin, the effect of improving the wetting between the abrasive grains 12 having the glass frit 14 and the vitrified bond 20 is not sufficiently exhibited. For example, the average thickness of the glass frit 14 is preferably 0.1 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. Note that the thickness of the glass frit 14 can be obtained, for example, using the volume ratio of the abrasive grains to the glass frit and the BET specific surface area of the abrasive grains. Further, it can be obtained by calculating the average value of the thicknesses of the glass frit at a plurality of arbitrarily set locations (e.g., 10 locations) in the elemental map of the constituent element (e.g., boron) of the glass frit in the cross section of the abrasive.

[0037] In a preferred embodiment, the abrasive grains are composed of diamond, and it is preferable that a glass flux adheres to the surface of the diamond as such abrasive grains. When diamond is used as the abrasive grains, it is necessary to fire at a relatively low temperature (for example, 700 °C or lower) in order to suppress the oxidation of diamond. Further, the wettability between diamond and the vitrified bond 20 which is an oxide tends to be low. On the other hand, since the glass flux adheres to the surface of the diamond as the abrasive grains, even when fired at a relatively low temperature, the melting and softening of the vitrified bond 20 can be promoted. Therefore, when the abrasive grains are composed of diamond, the effect of the glass flux adhering to the surface thereof can be more significantly exhibited.

[0038] Also, in another preferred embodiment, the abrasive grains are composed of cubic boron nitride (CBN), and it is preferable that a glass flux adheres to the surface of the CBN as such abrasive grains. When the abrasive grains are composed of CBN, when mixed with the vitrified bond 20 and fired, there is a risk that the CBN and the vitrified bond 20 react with each other and the abrasive grains become dull. Further, at the boundary between the abrasive grains and the vitrified bond 20, the generation of boron oxide may reduce the abrasive grain holding force. On the other hand, since the glass flux adheres to the surface of the CBN as the abrasive grains, for example, when heat treatment is carried out to manufacture the grindstone 100, the glass flux reacts more actively with the vitrified bond 20, so that it is possible to suppress the dulling of the abrasive grains (CBN). In this case, it is more preferable that the glass flux contains a compound containing boron. Thereby, the diffusion of boron from the abrasive grains (CBN) to the vitrified bond 20 can be more suitably suppressed.

[0039] According to the technology disclosed herein, an abrasive (powder material) used in the production of a vitrified grinding wheel is provided. The abrasive (powder material) is preferably substantially composed of abrasive grains 12 with a glass flux 14 attached to the surface. Here, "substantially composed of" means that the presence ratio of the abrasive grains 12 with the glass flux 14 attached to the surface is prominent, and it means that it contains 60% by number or more, 80% by number or more, more preferably 90% by number or more, and still more preferably 95% by number or more of all the abrasive grains constituting the abrasive (powder material).

[0040] <Grinding wheel> As shown in FIG. 2, the grinding wheel 100 includes a plurality of abrasive grains 12 and a vitrified bond 20, and is configured by bonding the plurality of abrasive grains 12 together with the vitrified bond 20. Further, the grinding wheel 100 is a porous body having a plurality of voids 30. Such voids 30 function as a space for temporarily storing grinding chips when grinding a workpiece.

[0041] The vitrified bond 20 is a binder that binds a plurality of abrasive grains 12 to each other. The vitrified bond 20 can be used without particularly limiting the conventionally known vitrified bond. For example, the vitrified bond 20 is a glassy binder mainly composed of Bi2O3-ZnO-B2O3-SiO2-based glass, SiO2-RO (R represents, for example, Mg, Ca, Zn, Ba, Sr. The same applies hereinafter) -based glass, SiO2-R'2O (R' represents, for example, Li, K, Na. The same applies hereinafter) -based glass, 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 two or more components in addition to the above glass components. Also, one of the above glass components may be used alone, or two or more may be mixed and used.

[0042] In the grinding wheel 100, the concentration of the glass flux component is different between the position P1 where the abrasive grains 12 and the vitrified bond 20 are in contact and the position P2 where the abrasive grains 12 and the vitrified bond 20 are not in contact. Here, the "glass flux component" refers to at least one of boron, lead, fluorine, alkali metal elements, and alkaline earth metal elements. 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 are in contact is High higher than the concentration of the glass flux component at the position P2 where the abrasive grains 12 and the vitrified bond 20 are not in contact. Such a concentration may have a concentration gradient that decreases stepwise or continuously from the position P1 in contact with the abrasive grains 12 to the position P2 not in contact with the abrasive grains 12. Thereby, the abrasive grains 12 are suitably held by the vitrified bond 20.

[0043] As an example, the case where the glass flux component is boron will be described. In this case, the concentration of boron at the position P1 where the abrasive grains and the vitrified bond are in contact is High higher than the concentration of boron at the position P2 where the abrasive grains and the vitrified bond are not in contact, which is preferable. Specifically, for example, taking the surface of the abrasive grain as point a, and a point located in a region not in contact with the abrasive grain, which is more than 3 μm away from point a and also more than 3 μm away from other abrasive grains as point b. At this time, the concentration B of boron at point b is smaller than the concentration A of boron at point a (concentration A > concentration B). For example, the ratio (concentration A / concentration B) of the concentration A of boron at point a to the concentration B of boron at point b is preferably 1.1 or more, may be 1.2 or more, and may be 1.3 or more. The concentration of boron at each point can be measured using EPMA (Electron Probe Micro Analyzer). Also, in the above, the case where the glass flux component is boron was described as an example, but the same applies when the glass flux component is lead (Pb), fluorine (F), alkali metal elements, alkaline earth metal elements, etc.

[0044] In the grinding wheel 100, it is preferable that the softening point of the vitrified bond 20 is different between the position P1 where the abrasive grains 12 and the vitrified bond 20 are in contact and the position P2 where the abrasive grains 12 and the vitrified bond 20 are not in contact. Specifically, in the grinding wheel 100, the softening point of the vitrified bond 20 at the position P1 where the abrasive grains 12 and the vitrified bond 20 are in contact is preferably lower than the softening point of the vitrified bond 20 at the position P2 where the abrasive grains 12 and the vitrified bond 20 are not in contact. For example, taking the surface of the abrasive grain 12 as point a, and a point located in a region not in contact with the abrasive material, which is more than 3 μm away from point a and also more than 3 μm away from other abrasive grains as point b. At this time, 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 may be 50 °C or more. The softening point of the vitrified bond at each point can be obtained by measuring a bond reproducing the compositions of point a and point b with a TMA (Thermomechanical Analyzer). The compositions of point a and point b can be measured using EPMA.

[0045] In the grinding wheel 100, the ratio of the abrasive grains 12 in the entire grinding wheel (that is, the total of the abrasive grains 12 and the vitrified bond 20) can be appropriately set according to the use of the grinding wheel and the like. If the ratio of the abrasive grains 12 is too low, the grinding efficiency may decrease, which is not preferable. On the other hand, if the ratio of the abrasive grains 12 is too high, the ratio of the vitrified bond 20 relatively decreases, and the abrasive grains 12 are not preferably fixed. For this reason, there is a risk that the abrasive grains 12 may fall off or the vitrified bond 20 may crack, etc., resulting in a decrease in durability, which is not preferable. Therefore, the ratio of the 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. Note that the grinding wheel 100 disclosed here may contain additives such as dispersants and foaming agents and decomposition products thereof within a range that does not impair the object of the present invention.

[0046] <Method for manufacturing grinding wheel> Next, an example of a method for manufacturing a vitrified grinding wheel disclosed herein will be described. Such a manufacturing method includes at least a step (A) of preparing an abrasive material having a glass flux 14 adhered to the surface of abrasive grains 12, and a 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 the step (B), the glass flux 14 and the vitrified bond 20 are reacted to promote melting or softening of the vitrified bond 20 in the vicinity of the surface of the abrasive grains 12, and other manufacturing processes may be the same as those in the prior art. Further, the manufacturing method disclosed herein may further include other steps at any stage.

[0047] In the step (A), an abrasive material having a glass flux 14 adhered to the surface of abrasive grains 12 is prepared. The step (A) is not particularly limited as long as the glass flux 14 can be adhered to the surface of the abrasive grains 12. For example, the glass flux 14 can be adhered 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. Alternatively, the glass flux 14 can also be adhered to the surface of the abrasive grains 12 by a vapor phase method such as CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition), a liquid phase reduction method, a hydrothermal synthesis method, a coprecipitation method, or the like.

[0048] Here, as an example of step (A), the attachment of the glass frit 14 to the surface of the abrasive grains 12 by mixing the abrasive grains 12 and the glass frit 14 or a material containing the glass frit will be described. For example, step (A) may include a mixing process (hereinafter also referred to as "first mixing process") of mixing a liquid medium, the abrasive grains 12, and the glass frit 14 or a material containing the glass frit, and a preliminary heat treatment for removing the liquid medium after the first mixing process. The mixing method of the materials in the first mixing process is not particularly limited, and for example, it can be carried out using various known mixing devices such as a three-roll mill, a magnetic stirrer, a planetary mixer, and a disperser. Further, the preliminary heat treatment is not particularly limited as long as the liquid medium can be removed. For example, it is preferable to heat at a temperature of about 50°C to 150°C for about 30 minutes to 4 hours. Further, the preliminary heat treatment may be carried out in a reduced-pressure environment.

[0049] Examples of the abrasive grains 12 include particles made of the above-described minerals, carbides, oxides, nitrides, etc. of metals or semi-metals. For example, diamond or CBN can be preferably used. Examples of the glass frit include compounds containing boron (B), lead (Pb), fluorine (F), alkali metal elements, and alkaline earth metal elements. Preferably, boric acid powder, Ca resinate, borax, soluble compounds containing the above elements, etc. are included.

[0050] The liquid medium can be, for example, a solvent that dissolves the glass frit 14 or a dispersion medium that disperses the glass frit 14. The liquid medium may be aqueous or organic. As the aqueous liquid medium, water or a mixed liquid mainly composed of water (for example, a mixed solution of water and ethanol) can be used. Further, as the organic liquid medium, for example, alcohol-based such as squalene, citronellol, phytol, geranyl linalool, texanol, benzyl alcohol, ethanol, phenoxyethanol, 1-phenoxy-2-propanol, terpineol, dihydroterpineol, isoborneol, butyl carbitol, diethylene glycol, etc.; ester-based such as terpineol acetate, dihydroterpineol acetate, isobornyl acetate, carbitol acetate, diethylene glycol monobutyl ether acetate, etc.; and mineral spirit, etc. Among them, alcohol-based and ester-based liquid media can be preferably used. Note that the liquid medium may be used alone or in combination of two or more.

[0051] Preferably, in the first mixing process, the glass frit 14 is dissolved in the solvent. In another preferred embodiment, in the first mixing process, the glass frit 14 is dispersed in the dispersion medium. By these, it can be attached to the surface of the abrasive grains 12 in a state where the bias of the glass frit 14 is small.

[0052] Step (A) preferably further includes a process of firing abrasive grains 12 to which a glass frit 14 is adhered. The firing process in Step (A) (hereinafter, also referred to as "the first firing process") may be carried out under conditions such that the glass frit 14 adhered to the surface of the abrasive grains 12 is stabilized, and is not particularly limited. The first firing process is preferably carried out in an oxidizing atmosphere (for example, in the air, etc.). Also, since the maximum firing temperature of the firing process in Step (A) varies depending on the types of the abrasive grains 12 and the glass frit 14, it cannot be generally defined, but for example, it is preferably 150°C or higher and 1000°C or lower, and may be 200°C or higher and 900°C or lower, or may be 300°C or higher and 800°C or lower. When diamond is used as the abrasive grains 12, if the maximum firing temperature is too high, there is a risk that the diamond will oxidize, so it is preferably set to 700°C or lower, for example. The firing time is not particularly limited, but it is preferably fired for about 30 minutes to 4 hours, for example.

[0053] In Step (B), a mixture containing an abrasive material and a vitrified bond 20 is fired. Specifically, Step (B) may include a mixing process (hereinafter, also referred to as "the second mixing process") of mixing the abrasive material, the vitrified bond 20, and a binder until they become paste-like, a process of forming the mixture, and a firing process of firing the formed body. The stirring and mixing method in the second mixing process is not particularly limited, and it can be carried out using various conventionally known stirring and mixing devices described above. The forming process is not particularly limited, but for example, it can be formed by press forming or the like.

[0054] As the vitrified bond 20, glass powder having the composition as described above after firing can be used without particular limitation. From the viewpoint of fixing property for preferably binding the abrasive grains 12, glass powder including Bi2O3-ZnO-B2O3-SiO2-based glass, SiO2-B2O3-R2O-RO-based glass, etc. can be preferably used.

[0055] The binder has a function of binding a plurality of abrasive grains 12 to each other and binding the abrasive grains 12 and the vitrified bond 20 at a stage before firing. Thereby, the shape stability until firing can be improved. On the other hand, the binder can become an unnecessary component after the abrasive grains 12 and the vitrified bond 20 are integrated by firing. Therefore, it is preferably a component that is burned out by firing and does not remain in the grinding wheel 100 after firing. As such a binder, an organic compound having a binder function can be used without particular limitation. For example, specifically, 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, phenol resins, alkyd resins, polyvinyl alcohol, polyvinyl butyral, and other vinyl-based resins, and binder resins based on rosin-based resins such as rosin and maleated rosin are preferably used. Note that the binder may be used alone or in combination of two or more. In addition, the grinding wheel 100 can contain various additives other than the above within a range not departing from the object of the present invention. Preferred examples of such additives include additives such as pore formers, surfactants, defoamers, antioxidants, dispersants, and rheology modifiers.

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

[0057] In step (B), after the second mixing process, a process of drying a mixture containing an abrasive and a vitrified bond 20 or the like may be included. Although the drying process is not particularly limited, for example, it may be dried at a temperature of about 50°C to 120°C for about 1 hour to 6 hours. For drying, conventionally known drying methods such as ventilation drying, heat drying, and vacuum drying can be used. And after the drying process, it is preferable to perform a shaping process.

[0058] In step (B), a firing process (hereinafter, also referred to as "second firing process") may be performed under conditions such that the glass flux 14 contained in the abrasive prepared in step (A) does not remain in its prepared state. Thereby, the fluidity of the vitrified bond 20 in the vicinity of the surface of the abrasive grains 12 can be more preferably increased. Further, a decrease in strength due to the remaining of the glass flux 14 in the manufactured grindstone 100 is suppressed. Specifically, step (B) may be performed under conditions such that the glass flux prepared in step (A) is preferably oxidized by firing so that the composition of the glass flux in step (B) is different from the composition of the glass flux in step (A). Further, step (B) may be performed under conditions such that the glass flux prepared in step (A) is preferably melted by firing so that the shape of the glass flux in step (B) is different from the shape of the glass flux in step (A).

[0059] In step (B), the mixture of the abrasive and the vitrified bond 20 may be fired at a temperature higher than the softening point of the vitrified bond 20. Thereby, the glass flux 14 contained in the abrasive is reacted with the vitrified bond 20, and melting and softening of the vitrified bond 20 are promoted in the vicinity of the surface of the abrasive grains 12. For this reason, even when firing is performed at a relatively low temperature (for example, 700° C. or lower) or when abrasive grains 12 having low wettability with the vitrified bond 20 are used, the abrasive grain holding force in the fired grinding wheel 100 can be suitably improved. Here, when a material that is easily oxidized (for example, diamond) is used as the abrasive grains 12, it is necessary to set the temperature during firing relatively low (typically 800° C. or lower, for example, 700° C. or lower in the atmosphere). Also, diamond is generally known to have poor wetting with the vitrified bond 20. In the technique disclosed herein, since the glass flux 14 adheres to the surface of the diamond as the abrasive grains 12, the above-described effects are suitably exhibited, and thus, a grinding wheel 100 having high strength can be realized even when fired at a relatively low temperature.

[0060] The firing process (second firing process) in step (B) is preferably carried out in an oxidizing atmosphere (for example, in the air or the like). The maximum firing temperature in the second firing process varies depending on the type of the abrasive and the vitrified bond 20, and thus is not generally defined, but it 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 the firing of step (B) is preferably 300° C. or higher and 1000° C. or lower, may be 400° C. or higher and 800° C. or lower, or may be 450° C. or higher and 700° C. or lower. Also, the firing time is not particularly limited, but for example, firing may be performed for about 1 hour to 10 hours.

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

[0062] The vitrified grinding wheel disclosed herein can be applied to the grinding of workpieces having various materials and shapes. The material of the workpiece can be, for example, a metal or semi-metal material such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, etc., or an alloy thereof; a glass material such as quartz glass, aluminosilicate glass, glassy carbon, etc.; a ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide, etc.; a semiconductor substrate material such as silicon carbide, gallium nitride, gallium arsenide, etc.; and the like. It may also be a workpiece composed of a plurality of these materials. Among them, it is suitable for grinding workpieces made of metal materials or semiconductor materials. Since the vitrified grinding wheel disclosed herein has high abrasive grain holding power and improved durability, it can be suitably used for high-load grinding such as ultra-high-speed grinding.

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

[0064] Item 1: A method for manufacturing a vitrified grinding wheel, comprising a step (A) of preparing an abrasive material having a glass flux adhered to the surface of abrasive grains, and a step (B) of firing a mixture containing the abrasive material and a vitrified bond, wherein the step (B) is characterized in that the glass flux and the vitrified bond are reacted to promote melting or softening of the vitrified bond in the vicinity of the surface of the abrasive grains.

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

[0066] Item 3: The manufacturing method according to Item 1 or 2, wherein in the step (A), a mixing process of mixing the abrasive grains and the glass flux or a material containing the glass flux is included.

[0067] Item 4: The manufacturing method according to any one of Items 1 to 3, including a firing process of firing an abrasive material with the glass frit adhering to the surface of the abrasive grains in the above step (A).

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

[0069] Item 6: The manufacturing method according to any one of Items 1 to 5, wherein the firing in the above 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 above step (B), the ratio (Y / X) of the weight Y of the glass frit to the weight X of the vitrified bond is 0.1 or less.

[0071] Item 8: An abrasive material used for manufacturing a vitrified grinding wheel, comprising abrasive grains and a glass frit adhering to the surface of the abrasive grains, and the adhered amount of the glass frit in terms of volume per unit surface area of the abrasive grains is 0.2 mm 3 / m 2 or more and 50 mm 3 / m 2 or less.

[0072] Item 9: The abrasive material according to Item 8, wherein the glass frit 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 any one of diamond and cubic boron nitride.

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

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

[0076] Item 13: The grinding material according to any one of items 8 to 12, wherein the content of the glass frit is 10 wt% or less when the total grinding material is 100 wt%.

[0077] Item 14: The amount of glass frit adhered per unit area (mg / m 2 ) of the abrasive grains is 0.02 mg / m 2 or more and 50 mg / m 2 or less, and the grinding material according to any one of items 8 to 13.

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

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

[0080] <Test Example> Hereinafter, examples related to the technology disclosed herein will be described, but it is not intended to limit the technology disclosed herein to those shown in such examples.

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

[0082] 1. Preparation of grinding material (1) Grinding material A First, 20 g of diamond (manufactured by Global Diamond Co., Ltd., FRM4-6), 0.094 g of boric acid (0.053 g in terms of B2O3), and 25 g of ethanol were prepared. After dissolving boric acid in ethanol, diamond was further added and stirred. Then, a mixture was obtained by performing dispersion treatment using an ultrasonic cleaner. This mixture was dropped onto a glass plate placed on an 80°C hot plate and dried. Further, the glass plate was placed in a vacuum oven at 80°C and dried in the vacuum oven for 1 hour, and this dried product was crushed using a mortar. Thereafter, firing was performed in an air atmosphere under the conditions of a temperature of 600°C, a heating rate of 10°C / min, and a heat treatment time of 30 minutes. As a result, boric acid was oxidized, and a fired product with boron oxide (B2O3) adhering to the surface of the diamond (abrasive grains) was obtained. The obtained fired product was crushed using a mortar to prepare grinding material A.

[0083] (2) Grinding material B The diamond (manufactured by Global Diamond Co., Ltd., FRM4-6) used for grinding material A was used as grinding material B as it was without attaching a glass flux.

[0084] (3) Grinding material C 20 g of diamond (manufactured by Global Diamond Co., Ltd., FRM4-6) used for grinding material A, 0.88 g of Si resinate (content in terms of SiO2 is 7.15 wt%, 0.063 g in terms of SiO2), and 25 g of ethanol were prepared. After dissolving boric acid in ethanol, diamond was further added and stirred. Then, a mixture was obtained by performing dispersion treatment using an ultrasonic cleaner. This mixture was dropped onto a glass plate placed on an 80°C hot plate and dried. Further, the glass plate was placed in a vacuum oven at 80°C and dried in the vacuum oven for 1 hour, and this dried product was crushed using a mortar. Thereafter, heat treatment was performed in an air atmosphere under the conditions of a temperature of 600°C, a heating rate of 10°C / min, and a heat treatment time of 30 minutes. As a result, a fired product with silicon oxide adhering to the surface of the diamond (abrasive grains) was obtained. The obtained fired product was crushed using a mortar to prepare grinding material C.

[0085] 2. Evaluation of Grinding Media (1) BET Measurement Each grinding media was tested using a specific surface area measuring device (model number: BELSORP-max) manufactured by MicrotracBEL Corp. The N2 adsorption isotherm at -196°C was measured, and the BET specific surface area was determined based on the BET multi-point method. Also, the BET specific surface area of grinding media B was adopted as the BET specific surface area A (m 2 / g) of the abrasive grains, and the ratio (B / A) of the BET specific surface area B (m 2 / g) of the abrasive grains with the glass flux attached to the BET specific surface area A (m 2 / g) of the abrasive grains 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 grinding media, the average thickness (nm) of the adherent material and the content (wt%) of the adherent material were calculated. Also, using the weight (g) of the constituent materials of each grinding media and the density of the constituent materials of each grinding media (diamond: 3.52 g / cm 3 , B2O3: 1.85 g / cm 3 , SiO2: 2.2 g / cm 3 ), the content (vol%) of the adherent material in terms of volume conversion was calculated. Also, using the measured BET specific surface area and the content values, the amount of adherent per unit surface area of the abrasive grains and the amount of adherent in terms of volume conversion per unit surface area of the abrasive grains were calculated. The results are shown in Table 1.

[0087] 3. Preparation of Grinding Wheel Test Specimens (1) Example 1 8.12 g of the above-prepared abrasive A, 7.89 g of Bi2O3-ZnO-B2O3-SiO2-based glass powder (TMX-501F manufactured by TOMATEC Co., Ltd.) as a vitrified bond raw material powder, 1.97 g of a pore-forming agent (Technopolymer, MB30X-8Y manufactured by Sekisui Chemical Co., Ltd.), and 3.03 g of a binder (Oricox #2435E manufactured by Kyoeisha Chemical Co., Ltd.) were prepared. The abrasive A, glass frit, pore-forming agent, and binder were mixed using a stirrer (Awatori Rentaro, AR-550L-2) until they became a paste. The resulting mixture was dried at 100 °C for 4 hours and then crushed using a mortar to obtain grinding wheel base clay. 3.0 g of this grinding wheel base clay was press-molded so that the length was 55 mm, the width d was 6.5 mm, and the thickness h was 4 mm, and five molded bodies were prepared. These molded bodies were fired under the conditions of heating to 400 °C over 5 hours and holding at 400 °C for 2 hours, and then heating to 570 °C over 1 hour and 40 minutes and holding at 570 °C for 2 hours in an air atmosphere. The fired molded bodies were cooled over 4 hours or more, and five grinding wheel test pieces according to Example 1 were produced.

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

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

[0090] 4. Evaluation of Grinding Wheel Test Pieces (1) Measurement of Three-Point Bending Strength and Calculation of Three-Point Bending Elastic Modulus For the grinding wheel test pieces of Examples 1 to 3 (five each), a three-point bending strength test was performed using EZ-test manufactured by Shimadzu Corporation, and the arithmetic mean value was calculated. In this test, the distance L between the fulcrums of the support tool for fixing the grinding wheel test piece was set to 30 mm. Also, the pressurization rate during the test was set to 0.5 mm / min. The results are shown in Table 1. The three-point bending elastic modulus is given by the following formula: Three-point bending elastic modulus = (L 3 / 4dh 3)×(ΔF / Δs); where L is the distance between the fulcrums (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 the bending load of the test piece at 25% - 50% of the yield load, and Δs is the change in the deflection of the test piece at 25% - 50% of the yield load. Also, the three-point bending elastic modulus was calculated five by five for each example, and the arithmetic mean value was obtained. The results are shown in Table 1.

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

[0092]

Table 1

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

[0094] As shown in Figures 3 to 5, in Example 1, it can be seen that the exposure amount of the abrasive grains is less and the wetting between the abrasive grains and the vitrified bond is good compared with Examples 2 and 3. This is presumably due to the fact that in the heat treatment for generating the grinding wheel, boron oxide functions as a glass flux and enhances the fluidity of the vitrified bond in the vicinity of the abrasive grains. Thereby, it is presumed that in Example 1, the abrasive grain holding force in the grinding wheel after heat treatment is improved.

[0095] In addition, since the BET specific surface area of Example 1 with boron oxide attached is equivalent to that of Example 2 without the attachment material, it can be seen that the structure of the attached boron oxide is not particulate. It is presumed that this is because boric acid was calcined during the heat treatment for producing the abrasive, and the generated boron oxide adhered to the surface of the abrasive grains in an amorphous form. On the other hand, since the BET specific surface area of Example 3 with silicon oxide attached is larger than that of Example 2 without the attachment material, it can be seen that the attached silicon oxide is particulate. It is presumed that this is because silicon oxide adhered to the surface of the abrasive grains as particles during the heat treatment for producing the abrasive. Furthermore, as shown in Table 1, although silicon oxide is attached in Example 3, the three-point bending elastic modulus of the grinding wheel test piece is the same as that of Example 2 without the attachment material, and the three-point bending strength is lower than that of Example 2. These are presumably because silicon oxide generally does not function as a glass frit, so it does not improve the wetting between the abrasive grains and the vitrified bond and does not enhance the abrasive grain holding force.

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

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

[0098] (2) Abrasive E Abrasive E was prepared in the same manner as abrasive D, except that the amount of boric acid was increased by 10 times (i.e., 0.94 g).

[0099] (3) Abrasive F Instead of boric acid, 1.05 g of Ca resinate (content in terms of CaO is 9.08 wt%) (0.095 g in terms of CaO) was prepared. Abrasive F was prepared in the same manner as abrasive D, except for this.

[0100] (4) Abrasive 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 this.

[0101] (5) Abrasive H The diamond (manufactured by Global Diamond Co., Ltd., FRM-DN 4-6) used for abrasive D was used as abrasive H as it was without attaching a glass flux.

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

[0103] 2. Evaluation of Grinding Materials (1) BET Measurement Each grinding material was tested using a specific surface area measuring device (model number: BELSORP-max) manufactured by Microtrac BEL Corporation. The N2 adsorption isotherm at -196 °C was measured, and the BET specific surface area was determined based on the BET multipoint method. Also, the BET specific surface area of grinding material H was adopted as the BET specific surface area A (m 2 / g) of the abrasive grains, and the ratio (B / A) of the BET specific surface area B (m 2 / g) of the abrasive grains with the glass frit attached to the BET specific surface area A (m 2 / g) of the abrasive grains 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 grinding material, the average thickness (nm) of the adhering material (glass frit) and the content (wt%) of the glass frit were calculated. Also, using the weight (g) of the constituent materials of each grinding material and the density of the constituent materials of each grinding material (diamond: 3.52 g / cm 3 , B2O3: 1.85 g / cm 3 , CaO: 3.34 g / cm 3 , Na2B4O7: 1.72 g / cm 3 ), the content in volume conversion (vol%) of the glass frit was calculated. Also, using the measured BET specific surface area and the content values, the adhesion amount per unit surface area of the abrasive grains and the adhesion amount in volume conversion per unit surface area of the abrasive grains were calculated. The results are shown in Table 2.

[0105] 3. Preparation of Grinding Wheel Test Pieces (1) Example 11 8.12 g of the above-prepared abrasive D, 7.89 g of Bi2O3-ZnO-B2O3-SiO2-based glass powder (TMX-501F manufactured by TOMATEC Co., Ltd.) as a vitrified bond raw material powder, 1.97 g of a pore-forming agent (Technopolymer, MB30X-8Y manufactured by Sekisui Chemical Co., Ltd.), and 3.03 g of a binder (Oricox, #2435E manufactured by Kyoeisha Chemical Co., Ltd.) were prepared. The abrasive D, glass frit, pore-forming agent, and binder were mixed using a stirrer (Awatori Rentaro, AR-550L-2) until they became a paste. The resulting mixture was dried at 100 °C for 4 hours and crushed using a mortar to obtain grinding wheel base clay. 3.0 g of this grinding wheel base clay was press-molded so that the length was 55 mm, the width d was 6.5 mm, and the thickness h was 4 mm, and five molded bodies were prepared. These molded bodies were fired under the conditions of heating to 400 °C over 5 hours and holding at 400 °C for 2 hours, then heating to 570 °C over 1 hour and 40 minutes and holding at 570 °C for 2 hours in an air atmosphere. The fired molded bodies were cooled over 4 hours or more, and five grinding wheel test pieces according to Example 11 were produced.

[0106] (2) Examples 12 to 16 Five grinding wheel test pieces according to Examples 12 to 16 were produced in the same manner as in Example 11, except that abrasive grains E to I were used instead of abrasive D, respectively.

[0107] 4. Evaluation of grinding wheel test pieces For the grinding wheel test pieces of Examples 11 to 16 (five each), a three-point bending strength test was performed using EZ-test manufactured by Shimadzu Corporation, and the arithmetic mean value was calculated. In this test, the distance L between the fulcrums of the fixture for fixing the grinding wheel test piece was set to 30 mm. Also, the pressurization rate during the test was set to 0.5 mm / min. The results are shown in Table 2. The three-point bending elastic modulus is given by the following formula: Three-point bending elastic modulus = (L 3 / 4dh 3) × (ΔF / Δs); was calculated. Here, L: distance between fulcrums (30 mm), d: width of the grinding wheel test piece (6.5 mm), h: thickness of the grinding wheel test piece (4 mm), ΔF: change amount of the bending load of the test piece at 25% - 50% of the yield load, and Δs: change amount of the deflection of the test piece at 25% - 50% of the yield load. Also, the three-point bending elastic modulus was calculated five by five for each example, and the arithmetic mean value was obtained. The results are shown in Table 2. Note that both the three-point bending strength and the three-point bending elastic modulus are values indicating the strength of the grinding wheel test piece. 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 the three-point bending elastic modulus of the grinding wheel test piece is improved compared to Example 15. Therefore, it can be seen that by using, as the material of the grinding wheel, a grinding material with a glass frit adhered to the surface of the abrasive grains regardless of the type of the glass frit, the grinding wheel strength of the grinding wheel can be improved.

[0110] On the other hand, in Example 16, both the three-point bending strength and the three-point bending elastic modulus of the grinding wheel test piece are decreased compared to Example 15. It can be seen that when the volume conversion adhesion amount per unit surface area of the abrasive grains is too large, the strength of the grinding wheel is decreased. Therefore, the volume conversion glass frit adhesion amount per unit surface area of the abrasive grains is preferably 0.2 mm 3 / m 2 or more and 50 mm 3 / m 2 or less.

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

Explanation of Reference Numerals

[0112] 12 abrasive grains 14 glass flux 20 vitrified bond 30 voids 100 grinding wheel

Claims

1. A method for manufacturing a vitrified grinding wheel, comprising: a step (A) of preparing an abrasive material having a glass flux adhered to the surface of abrasive grains; a step (B) of firing a mixture containing the abrasive material and a vitrified bond; 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. A method for manufacturing a vitrified grinding wheel.

2. In the step (B), the firing is carried out under firing conditions such that the glass flux contained in the abrasive material prepared in the step (A) does not remain in its prepared composition and shape. The manufacturing method according to Claim 1.

3. In the step (A), the manufacturing method according to Claim 1 or 2, comprising a mixing process of mixing the abrasive grains and the glass flux or a material containing the glass flux.

4. In the step (A), the manufacturing method according to Claim 1 or 2, comprising a firing process of firing the abrasive material having the glass flux adhered to the surface of the abrasive grains.

5. In the firing process of the step (A), firing is carried out at a temperature of 150°C or higher and 1000°C or lower. The manufacturing method according to Claim 4.

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

7. 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. The manufacturing method according to Claim 1 or 2.

8. An abrasive material used for manufacturing a vitrified grinding wheel, comprising: abrasive grains; a glass flux adhered to the surface of the abrasive grains; 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. The amount of glass frit adhesion in terms of volume per unit surface area of the abrasive grains is 0.2 mm ３ / m ２ 50 mm or less ３ / m ２ The abrasive material is as follows.

9. The abrasive material according to Claim 8, wherein the abrasive grains are either diamond or cubic boron nitride.

10. The abrasive material according to Claim 8, wherein the glass flux is partially adhered to the surface of the abrasive grains.

11. The BET specific surface area B (m ２ / g) of the abrasive grains with the glass frit adhered to the surface thereof with respect to the BET specific surface area A (m ２ / g) of the abrasive grains is 1.3 or less. The abrasive material according to claim 8.

12. The content of the glass flux is 10 wt% or less when the total abrasive material is 100 wt%. The abrasive material according to Claim 8.

13. The amount of glass frit adhesion per unit area of the abrasive grains (mg / m ２ 2) is 0.02 mg / m ２ or more and 50 mg / m ２ or less. The abrasive according to claim 8.

14. A vitrified grinding wheel comprising a plurality of abrasive grains and a vitrified bond that binds the plurality of abrasive grains to each other. The concentration of the glass flux component at the position P1 where the abrasive grains and the vitrified bond are in contact is higher than the concentration of the glass flux component at the position P2 where the abrasive grains and the vitrified bond are not in contact. Here, the glass flux component is at least one of boron, lead, fluorine, an alkali metal element, and an alkaline earth metal element, and it is a vitrified grinding wheel.

15. The softening point (°C) of the vitrified bond at the position P1 where the abrasive grains and the vitrified bond are in contact is lower than the softening point (°C) of the vitrified bond at the position P2 where the abrasive grains and the vitrified bond are not in contact. The vitrified grinding wheel according to claim 14. ​

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