JP2024126675A - Abrasives used in the manufacture of vitrified grinding wheels, and vitrified grinding wheels - Google Patents

Abstract

To provide an abrasive material which can contribute to an improvement in the strength of a petrified grind stone.SOLUTION: An abrasive material 10 disclosed here is an abrasive material used for the manufacture of a petrified grind stone. The abrasive material 10 contains an abrasive grain 12 and a coat material deposited on at least a part of the surface of the abrasive grain 12. The coat material in a technology disclosed here is an Al-Bi coat 14 containing at least Al and Bi. The use of the abrasive material 12 with the deposited Al-Bi coat 14 enables an improvement in the strength of a post-manufacture petrified grind stone.SELECTED DRAWING: Figure 1

Description

The technology disclosed herein relates to abrasives used in the manufacture of vitrified grinding wheels, and to vitrified grinding wheels.

Vitrified grinding wheels are widely used as an example of a tool for grinding metal materials, etc. In the manufacture of vitrified grinding wheels, a clay containing abrasive grains and a vitrified bond (a glassy binder) is fired. In this firing process, the molten vitrified bond flows through the gaps between the multiple abrasive grains. This forms a bond network in which multiple abrasive grains are bonded together via the vitrified bond. Examples of abrasive grains used in vitrified grinding wheels include diamond grains and cubic boron nitride (cBN) grains.

In the field of vitrified grinding wheels, a technique has been proposed in which abrasive grains are coated with a coating material. For example, in the technique described in Patent Document 1, a coating layer made of ceramics, not oxides, is formed on the surface of the abrasive grains. This is said to prevent the oxides in the vitrified bond from reacting with the abrasive grains during firing. In addition, in the technique described in Patent Document 2, the surface of the cBN abrasive grains is coated with an aluminum oxide layer or a silicon oxide layer. This is said to improve the adhesion between the cBN abrasive grains and the vitrified bond.

Japanese Patent Application Publication No. 4-331076 Japanese Patent Application Publication No. 7-108461

However, in recent years, as the hardness of workpieces increases, there is a demand for further improvements in the strength of vitrified grinding wheels. The technology disclosed here has been made in consideration of such demands, and aims to provide an abrasive material that can contribute to improving the strength of vitrified grinding wheels, and a vitrified grinding wheel that uses said abrasive material.

In order to achieve the above objective, the technology disclosed herein provides an abrasive having the following configuration. As will be described in detail later, in this specification, "abrasive" refers to a particulate material mainly composed of abrasive grains.

The abrasive material disclosed herein is an abrasive material used in the manufacture of vitrified grinding wheels. Such an abrasive material includes abrasive grains and a coating material attached to at least a portion of the surface of the abrasive grains. The coating material in the technology disclosed herein is an Al-Bi coating that includes at least Al and Bi.

The inventors of the present invention conducted experiments and studies to achieve the above object, and found that the strength of the vitrified grinding wheel after manufacture is improved by attaching a coating material containing Al and Bi (Al-Bi coating) to the surface of the abrasive grains. Although it is not intended to limit the technology disclosed herein, it is presumed that such an effect of improving the strength is achieved by the following actions. First, when abrasive grains with an Al-Bi coating are used in the manufacture of a vitrified grinding wheel, Al oxides and Bi oxides can be generated on the surface of the abrasive grains during the grinding wheel manufacturing process. These oxides have good wettability with the vitrified bond, so that a bond network between the abrasive grains is suitably formed by the vitrified bond. In addition, a part or all of these oxides can be incorporated into the vitrified bond during the grinding wheel manufacturing process. As a result, glass containing a large amount of Al ₂ O ₃ and Bi ₂ O ₃ is generated near the surface of the abrasive grains. Here, when the _amount of _Al2O3 and _Bi2O3 in the glass near the abrasive grains is increased, the softening fluidity during the grinding wheel manufacturing process is _improved , and the adhesion to the abrasive grains is improved. It is presumed that the above-mentioned action of the abrasive material disclosed herein improves the wettability between the abrasive grains and the vitrified bond during firing. As a result, the vitrified grinding wheel after manufacture has a strong bond network between the abrasive grains via the vitrified bond, and therefore exhibits excellent strength.

In a preferred embodiment of the abrasive material disclosed herein, the Al-Bi coating is a metal oxide or an organometallic compound. Regardless of the form of the Al-Bi coating, it can adequately exhibit the strength-improving effect described above.

In a preferred embodiment of the abrasive disclosed herein, the Al-Bi coating has a ratio of the number of moles of Al to the total number of moles of Al and Bi (Al/Al+Bi) of 0.1 or more and 0.9 or less. This allows the strength-improving effect of the Al-Bi coating to be more suitably exerted.

In a preferred embodiment of the abrasive material disclosed herein, the abrasive grains include one selected from the group consisting of diamond abrasive grains and cubic boron nitride abrasive grains. The technology disclosed herein is particularly suitable for use with these abrasive grains.

As another aspect of the technology disclosed herein, a vitrified grinding wheel is provided. Such a vitrified grinding wheel includes a plurality of abrasives and a vitrified bond that bonds the plurality of abrasives. The abrasives of the vitrified grinding wheel disclosed herein are the abrasives having the above-mentioned configuration. A vitrified grinding wheel having such a configuration has excellent strength because a strong bond network is formed via the vitrified bond.

In a preferred embodiment of the vitrified grinding wheel disclosed herein, the vitrified bond has an Al-Bi region near the surface of the abrasive grain that contains more Al and Bi than other regions. In the vitrified grinding wheel disclosed herein, an Al-Bi region resulting from the Al-Bi coating may be formed near the surface of the abrasive grain.

In a preferred embodiment of the vitrified grinding wheel disclosed herein, when elemental analysis based on energy dispersive X-ray analysis is performed on a cross-sectional SEM image, the ratio of the total number of Al and Bi atoms to the total number of atoms of metal elements and metalloid elements in the Al-Bi region is 30% or more. This allows the formation of a stronger bond network via the vitrified bond.

In one preferred embodiment of the vitrified grinding wheel disclosed herein, the vitrified bond is a glass material containing Bi. This can particularly effectively improve the strength of the vitrified grinding wheel.

FIG. 1 is a schematic diagram of an abrasive according to an embodiment. FIG. 2 is a flow chart showing an example of a procedure for manufacturing a vitrified grinding wheel. FIG. 3 is a diagram illustrating a vitrified grinding wheel according to one embodiment. FIG. 4 is an FE-SEM image of coating material A. FIG. 5 is an FE-SEM image of coating material B. FIG. 6 is an FE-SEM image of coating material C. FIG. 7 is an FE-SEM image of coating material D. FIG. 8 is an FE-SEM image of coating material E.

An embodiment of the technology disclosed herein is described below. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the conventional technology in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. Note that in this specification, the notation "A to B" indicating a numerical range means "A or more and B or less" unless otherwise specified. Note that the drawings are drawn diagrammatically, and the dimensional relationships in the drawings (length, width, thickness, etc.) do not reflect the actual dimensional relationships.

1. Abrasive Fig. 1 is a diagram showing a schematic diagram of an abrasive according to the present embodiment. As described above, the term "abrasive" in this specification refers to a particulate material mainly composed of abrasive grains. As shown in Fig. 1, the abrasive 10 according to the present embodiment includes abrasive grains 12 and an Al-Bi coating 14. Each component included in the abrasive 10 according to the present embodiment will be described below.

(1) Abrasive grains The abrasive grains 12 are particles having a predetermined hardness. The abrasive grains 12 have the function of directly grinding the workpiece in the vitrified grinding wheel after manufacture. The type of the abrasive grains 12 is not particularly limited, and appropriate particles can be appropriately selected from conventionally known particles that can be used as abrasive grains according to the nature of the workpiece and the mode of use. Examples of the components of the abrasive grains 12 include carbides, oxides, nitrides, etc. of minerals, metals, or semimetals. Specifically, the abrasive grains 12 can be diamond abrasive grains, cubic boron nitride (cBN) abrasive grains, silica abrasive grains, alumina abrasive grains, ceria abrasive grains, etc. The diamond abrasive grains here may be natural diamond or artificial diamond. Among these, the diamond abrasive grains and cBN abrasive grains are particularly preferably applicable to the technology disclosed herein. Specifically, diamond abrasive grains have a high Knoop hardness of 4000 or more (typically, about 7000 to 8000), so that they can easily process workpieces with high hardness. However, in the manufacture of vitrified grinding wheels using diamond abrasive grains, it is necessary to set the firing temperature at a low temperature (for example, 700° C. or less) in order to suppress oxidation of the abrasive grains. As a result, the fluidity of the vitrified bond during firing cannot be sufficiently ensured, and there is a possibility that poor formation of a bond network occurs in the manufactured vitrified grinding wheel. In contrast, according to the technology disclosed herein, the wettability between the vitrified bond and the abrasive grains 12 can be sufficiently improved by the Al-Bi coat 14 described later. As a result, even if low-temperature firing is performed to prevent oxidation of the diamond abrasive grains, a vitrified grinding wheel having a strong bond network can be manufactured. On the other hand, cBN abrasive grains also have a high Knoop hardness of 4000 or more (about 4700). However, the cBN abrasive grains may react with the vitrified bond during firing. In this case, the cBN abrasive grains are reduced, which may reduce the machining ability of the vitrified grinding wheel after manufacture. In contrast, in the technology disclosed herein, the surfaces of the abrasive grains 12 are coated with the Al-Bi coating 14, which can suppress the reaction between the vitrified bond and the cBN abrasive grains.

The size of the abrasive grains 12 does not limit the technology disclosed herein, and can be changed as appropriate depending on the purpose and manner of use. For example, the average grain size of the abrasive grains 12 may be 0.05 μm or more, 0.1 μm or more, 0.5 μm or more, or 1 μm or more. The average grain size of the abrasive grains 12 may be 1000 μm or less, 500 μm or less, 100 μm or less, 50 μm or less, or 25 μm or less. In this specification, the "average grain size" is the arithmetic mean of the circle-equivalent diameters of 100 or more grains observed with an electron microscope or the like.

The shape of the abrasive grains 12 is not particularly limited and can be appropriately selected from conventionally known shapes. For example, the abrasive grains 12 may be spherical, plate-like, or irregularly shaped (such as a confetti-like shape). The average aspect ratio of the abrasive grains 12 may be 1 to 2, or 1.1 to 1.8. In this specification, the "aspect ratio" can be determined by drawing a rectangle circumscribing the abrasive grain in an electron microscope image and calculating the ratio (b/a) of the length of the short side (a) to the length of the long side (b) of the rectangle. The "average aspect ratio" is the arithmetic mean value of the aspect ratios of 100 or more particles.

Moreover, it is preferable that the abrasive grains 12 have a BET specific surface area of a certain value or less. By using the abrasive grains 12 having a low BET specific surface area, the formation of the Al-Bi coat 14 described later tends to be facilitated. Specifically, the BET specific surface area of the abrasive grains 12 is preferably 100 m ² /g or less, more preferably 80 m ² /g or less, even more preferably 40 m ² /g or less, and particularly preferably 10 m ² /g or less. On the other hand, the lower limit of the BET specific surface area of the abrasive grains 12 is not particularly limited, and may be 0.01 m ² /g or more, 0.1 m ² /g or more, 0.5 m ² /g or more, or 1 m ² /g or more. In this specification, the "BET specific surface area" refers to a value obtained by analyzing an adsorption isotherm measured by a gas adsorption method using nitrogen (N ₂ ) gas as an adsorbate, using the BET method.

(2) Al-Bi Coating The Al-Bi coating 14 is a coating material attached to the surface of the abrasive grains 12. This Al-Bi coating 14 contains at least aluminum (Al) and bismuth (Bi). As will be described in detail later, by attaching the Al-Bi coating 14 to the abrasive grains 12, the wettability between the abrasive grains 12 and the vitrified bond during firing can be significantly improved. As a result, a strong bond network between the abrasive grains via the vitrified bond is formed, making it possible to manufacture a vitrified grinding wheel with excellent strength.

The Al-Bi coating 14 may be a metal oxide or an organic metal compound (resinate). As will be described in detail later, the Al-Bi coating 14 is understood to improve the wettability between the abrasive grains 12 and the vitrified bond by generating an Al oxide (Al ₂ O ₃ , etc.) and a Bi oxide (Bi ₂ O _3, etc.) on the surface of the abrasive grains 12 during firing. In contrast, when the Al-Bi coating 14 is a metal oxide, the Al oxide and the Bi oxide are already present on the surface of the abrasive grains 12, so that the effect of improving the wettability is easily exhibited. On the other hand, when the Al-Bi coating 14 is an organic metal compound, the organic metal compound is decomposed in the early stage of the firing process, and an Al oxide and a Bi oxide are generated on the surface of the abrasive grains 12. Even in such a case, the wettability between the abrasive grains 12 and the vitrified bond during firing can be improved. When the Al-Bi coating 14 is a metal oxide, the Al-Bi coating 14 may be a mixture of fine Al oxide and Bi oxide, or a composite oxide containing Al element and Bi element.

It is preferable that the ratio of the number of moles of Al to the total number of moles of Al and Bi (Al/Al+Bi) of the Al-Bi coating 14 is within a predetermined range. This can more suitably improve the strength of the vitrified grinding wheel after manufacture. Specifically, the above Al/Al+Bi is preferably 0.1 or more, more preferably 0.15 or more, even more preferably 0.2 or more, and particularly preferably 0.25 or more. As a result, the Al-Bi coating 14 contains sufficient Al, so that the adhesion of the vitrified bond near the abrasive grains 12 during firing is more suitably improved. On the other hand, the above Al/Al+Bi is preferably 0.9 or less, more preferably 0.85 or less, even more preferably 0.8 or less, and particularly preferably 0.75 or less. As a result, the Al-Bi coating 14 contains sufficient Bi, so that the fluidity of the vitrified bond near the abrasive grains 12 during firing is more suitably improved. The "number of moles of metal elements" contained in the Al-Bi coating 14 can be measured by performing elemental analysis of the Al-Bi coating 14 of the abrasive material 10 using EDX.

It is preferable that the Al-Bi coating 14 is composed of Al and Bi as the main elements. Specifically, it is preferable that the majority of the total number of moles of the metal elements and metalloid elements confirmed by the elemental analysis by EDX in the Al-Bi coating 14 is Al and Bi. For example, when the total number of moles of metal elements in the Al-Bi coating 14 is 100 mol%, the ratio of the total number of moles of Al and Bi is 50 mol% or more (preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more). This makes it possible to more preferably exert the above-mentioned strength improvement effect. On the other hand, the upper limit of the ratio of the total number of moles of Al and Bi is not particularly limited, and may be 100 mol% or less, 99 mol% or less, or 95 mol% or less. Other metal elements that may be included in the Al-Bi coating 14 include Na, Mg, Zn, K, Ca, Ti, Fe, Mn, Sr, Y, Zr, Ce, Ba, and Li. Metalloid elements include Si, B, Sb, and Te.

Moreover, the Al-Bi coating 14 only needs to be attached to at least a part of the surface of the abrasive grain 12, and does not need to completely cover the entire surface of the abrasive grain 12. For example, the amount of the Al-Bi coating 14 attached to the weight (100 wt%) of the abrasive grain 12 may be 0.1 wt% or more (preferably 0.2 wt% or more, more preferably 0.3 wt% or more, and particularly preferably 0.5 wt% or more). This allows the strength improving effect of the Al-Bi coating 14 to be fully exhibited. On the other hand, the upper limit of the amount of the Al-Bi coating 14 attached may be 50 wt% or less, or 30 wt% or less. However, if the amount of the Al-Bi coating 14 attached is too large, there is a possibility that the interface between the abrasive grain 12 and the vitrified bond will peel off from the Al-Bi coating remaining without being incorporated into the vitrified bond in the manufactured vitrified abrasive grain. From this viewpoint, the upper limit of the amount of the Al-Bi coating 14 is preferably 20 wt % or less, more preferably 10 wt % or less, even more preferably 5 wt % or less, and particularly preferably 3 wt % or less. Note that the "content of the Al-Bi coating" in this specification can be determined by dissolving and removing the Al-Bi coating in a specified solvent, quantifying the Al and Bi components contained in the solution by ICP emission analysis or the like, and converting them into Al ₂ O ₃ and Bi ₂ O _3, respectively.

(3) Powder material The abrasive 10 having the above-mentioned configuration may be used in the form of a powder material (a group of fine particles) mainly composed of the abrasive 10. Here, "mainly composed of abrasive" means that the fine particles contained in the powder material in the largest amount by weight are the abrasive having the above-mentioned configuration (i.e., abrasive grains having an Al-Bi coating attached thereto). More specifically, the powder material of the abrasive preferably contains 50% by weight or more (preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more) of abrasive grains having an Al-Bi coating attached thereto. The powder material may contain fine particles other than the abrasive having the above-mentioned configuration, as long as the strength improving effect of the technology disclosed herein is not significantly impaired. Examples of such subcomponents include abrasive grains not having an Al-Bi coating attached thereto, silica particles, alumina particles, ceria particles, and organic binder particles.

2. Manufacturing method of vitrified grinding stone Next, an example of a manufacturing method of a vitrified grinding stone using the grinding material 10 having the above-mentioned configuration will be described. Fig. 2 is a flow chart showing an example of a procedure for manufacturing a vitrified grinding stone. As shown in Fig. 2, the manufacturing method of this vitrified grinding stone includes a preparation step S10, a preparation step S20, a molding step S30, and a firing step S40. Each step will be described below.

(1) Preparation step S10
In this step, an abrasive 10 (see FIG. 1) containing abrasive grains 12 with an Al-Bi coating 14 is prepared. For example, in the preparation step S10, a bonding process is performed to bond the Al-Bi coating 14 to the abrasive grains 12. may be carried out to produce the abrasive material 10. An example of such an attachment process is as follows.

First, the precursor of the Al-Bi coating 14 is dissolved in a liquid medium. This prepares a coating solution. The precursors include an organometallic compound containing Al (Al resinate) and an organometallic compound containing Bi (Bi resinate). The liquid medium includes an organic solvent (such as alcohol) capable of dissolving these resinates. Next, the abrasive grains 12 are dispersed in this coating solution. A drying process is then performed to remove the organic solvent. This causes the Al-Bi coating 14 in the form of an organometallic compound to adhere to the surface of the abrasive grains 12. The drying temperature at this time is preferably about 50°C to 100°C. The drying time is preferably about 30 minutes to 4 hours.

On the other hand, when forming an Al-Bi coating 14 in a metal oxide state, it is advisable to bake the abrasive grains 12 to which the organometallic compound is attached. This decomposes the organometallic compound, and the Al and Bi are each oxidized. As a result, the Al-Bi coating 14 in a metal oxide state is attached to the surface of the abrasive grains 12. The baking temperature at this time is preferably about 400°C to 700°C. The baking time is preferably about 15 minutes to 2 hours.

Note that the preparation step S10 is not limited to the above-mentioned attachment process, as long as the desired abrasive material 10 can be prepared. For example, the Al-Bi coating 14 may be attached to the surface of the abrasive grains 12 using physical vapor deposition (PVD).

(2) Preparation step S20
In this step, a clay containing the abrasive 10 and a vitrified bond is prepared. The viscosity of the clay is not particularly limited. For example, the clay may be clay-like or paste-like. The components of the clay will be described below.

(2-1) Abrasive The composition of the abrasive 10 has already been described, so a duplicate description will be omitted. The amount of the abrasive 10 added to the total weight (100 wt%) of the abrasive 10 and the vitrified bond in the clay is preferably 10 wt% or more, more preferably 20 wt% or more, and particularly preferably 30 wt% or more. As the content ratio of the abrasive 10 in the clay increases, the strength of the vitrified grinding wheel after manufacture tends to improve. On the other hand, the amount of the abrasive 10 added is preferably 70 wt% or less, more preferably 60 wt% or less, and particularly preferably 50 wt% or less. This ensures processing durability.

(2-2) Vitrified bond The vitrified bond is a vitrified bonding agent that bonds the abrasive grains 12 together in the vitrified grinding wheel after manufacture. The type of vitrified bond is not particularly limited, and an appropriate material can be appropriately selected from conventionally known glass materials that can be used as vitrified bonds according to the properties of the workpiece, the mode of use, and the like. Examples of such glass materials include Bi ₂ O ₃ —ZnO—B ₂ O ₃ —SiO ₂ based glass, SiO ₂ —RO (R represents, for example, Mg, Ca, Zn, Ba, or Sr; the same applies below) based glass, SiO ₂ —R' ₂ O (R' represents, for example, Li, K, or Na; the same applies below) based glass, SiO ₂ -RO-Al ₂ O ₃ based glass, SiO ₂ -RO-Bi ₂ O ₃ based glass, SiO ₂ -RO-Y ₂ O ₃ based glass, SiO ₂ -RO-B ₂ O ₃ based glass, SiO ₂ -Al ₂ O ₃ based glass, SiO ₂ -ZnO based glass, SiO ₂ -ZrO ₂ based glass, RO-R' _{2 O} Examples of the glass include O-based glass, RO-based glass, lead-based glass, lead-lithium-based glass, borosilicate-based glass, etc. The vitrified bond may be a mixture of a plurality of glass materials.

The average particle size of the vitrified bond powder is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 10 μm or less, and particularly preferably 1 μm or less. If the fine vitrified bond powder can be properly dispersed in the clay, the vitrified bond is appropriately distributed in the vitrified grinding wheel after firing, and the strength of the vitrified grinding wheel is further improved. On the other hand, the vitrified bond is usually mixed with other materials in the form of a fine powder material. Although it is not intended to limit the technology disclosed herein, the average particle size of the vitrified bond powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and particularly preferably 1.0 μm or more. As the vitrified bond powder becomes larger, it becomes easier to disperse the vitrified bond powder in the clay.

In addition, when manufacturing a vitrified grinding wheel using the grinding material 10 according to this embodiment, it is particularly preferable to use a glass material containing Bi as the vitrified bond. This Bi-based bond has a Bi element in common with the Al-Bi coat 14. It has a suitable affinity for the Al-Bi coat 14. Therefore, a stronger bond network can be formed in the vitrified grinding wheel after manufacture. For example, this Bi-based bond may have a Bi content (%) of 5 mol% or more (preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more) when the total number of moles is 100 mol%. In addition, considering the strength of the bond after firing, the upper limit of the Bi content in the vitrified bond is preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, and particularly preferably 40 mol% or less. The "Bi content (mol%)" mentioned above was measured according to the following procedure. First, X-ray fluorescence analysis (XRF) is performed on the vitrified bond to detect the ratio of metal elements and metalloid elements present in the measurement target. However, XRF has a problem in that the quantitative accuracy of boron (B) and lithium (Li) is low. For this reason, boron (B) is quantified by ICP-AES (inductively coupled plasma atomic emission spectroscopy), and lithium (Li) is quantified by atomic absorption spectrometry. Then, the ratio of Bi in the measured atoms (Bi, B, Na, Mg, Al, Si, Zn, K, Ca, Ti, Fe, Mn, Sr, Y, Zr, Ce, Ba, Li) is calculated to measure the "Bi content (mol%)".

The Bi-based bond may have _{a Bi2O3} content of 10 wt% or more (preferably 20 wt% or more, more preferably 30 wt% or more, even more preferably 40 wt% or more, and particularly preferably 50 wt% or more) in terms of weight ratio of oxide. This allows the bond to exhibit a more favorable affinity with the Al-Bi coat 14. On the other hand, the upper limit of _{the Bi2O3} content in terms of weight ratio of oxide may be 90 wt% or less, 80 wt% or less, 70 wt% or less, or 60 wt% or less.

Furthermore, the amount of vitrified bond added relative to the total weight (100 wt%) of the abrasive and vitrified bond in the clay is preferably 10 wt% or more, more preferably 20 wt% or more, and particularly preferably 30 wt% or more. As the content of vitrified bond in the clay increases, the strength of the vitrified grinding wheel after manufacture tends to improve. On the other hand, the amount of vitrified bond added is preferably 70 wt% or less, more preferably 60 wt% or less, and particularly preferably 50 wt% or less. This ensures a sufficient content of other components (particularly the abrasive 10).

(2-2) Other Additives The clay may contain additives other than the abrasive and the vitrified bond. Examples of such additives include a binder and a pore former.

The binder is a resin material that binds powder materials such as abrasive grains 12 and vitrified bond in the clay before firing. By using the binder, it becomes easier to mold the molded body in the molding step S30 described later. Examples of such binders include acrylic resins such as polybutyl methacrylate, polymethyl methacrylate, and polyethyl methacrylate, cellulose 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 resins such as rosin and maleated rosin. Two or more types of binders may be used in combination. The amount of binder added to the total weight (100 wt%) of the clay is preferably 1 wt% to 30 wt% (more preferably 10 wt% to 20 wt%). This makes it possible to prepare a clay with suitable moldability.

The pore-forming agent is a solid that is burned away by firing. Examples of such pore-forming agents include starch, carbon powder, activated carbon, and polymer organic materials (e.g., polyethylene, polypropylene, melamine resin, and polymethyl methacrylate (PMMA) resin). By adding these pore-forming agents to the clay, voids 30 (see FIG. 3) can be easily formed in the vitrified grinding wheel after firing. These voids 30 function as spaces for temporarily storing grinding waste when the workpiece is ground. The average particle size of the pore-forming agent is preferably 0.1 μm to 1000 μm, and more preferably 1 μm to 100 μm. This allows voids of a suitable size to be formed uniformly. The amount of pore-forming agent added to the total weight (100 wt%) of the clay is preferably 1 wt% to 20 wt% (more preferably 5 wt% to 15 wt%). This allows a vitrified grinding wheel with a suitable porosity to be manufactured.

Other examples of additives include surfactants, defoamers, antioxidants, dispersants, rheology modifiers, etc. As these additives, conventionally known materials can be used without any particular restrictions, so long as they do not significantly impair the strength-improving effect of the technology disclosed herein.

(3) Molding process S30
In this step, the prepared clay is molded into a desired shape. The shape of the molded body produced in this step is not particularly limited, and an appropriate shape can be selected depending on the purpose and use of the vitrified grinding wheel after production. Examples of the shape of the molded body (vitrified grinding wheel after manufacture) include a disk shape (including a doughnut shape), a triangular pyramid shape, a sphere shape, and a cylinder shape. The body may be in the form of chips obtained by dividing the above-mentioned shape into any desired shape. The means for molding the clay is not particularly limited, and any known means such as press molding can be used without particular limitation.

(4) Firing step S40
In this process, the molded body is fired. As a result, the organic components (binder, pore-forming agent, etc.) in the molded body are burned off and the vitrified bond, which is a glass material, is melted. The molten vitrified bond then flows through the gaps between the multiple abrasive grains 12 and diffuses throughout the molded body. The vitrified bond then solidifies after firing to form a bond network that bonds the multiple abrasive grains 12.

Here, in this embodiment, since the Al-Bi coat 14 is attached to the abrasive grains 12, Al oxides and Bi oxides can be generated on the surface of the abrasive grains 12 during firing. These oxides have good wettability with the vitrified bond, so a vitrified bond network between the abrasive grains 12 is suitably formed. In addition, some or all of these oxides may be incorporated into the vitrified bond during firing. As a result, glass containing a large amount of Al ₂ O ₃ and Bi ₂ O ₃ is generated near the surface of the abrasive grains 12. Here, if the amount of Al ₂ O ₃ and the amount of Bi ₂ O ₃ of the glass near the abrasive grains 12 increases, the softening fluidity during firing is improved, and the fixation of the vitrified bond to the abrasive grains 12 is improved. As a result, a strong bond network is formed in the vitrified grinding wheel after firing, so it is presumed that the strength of the vitrified grinding wheel is improved.

The firing conditions in the firing step S40 are preferably adjusted according to the type of abrasive grains 12 and vitrified bond. For example, the firing temperature is preferably equal to or higher than the softening point of the vitrified bond and is a temperature that can suppress the deterioration of the abrasive grains 12. A specific example of the firing temperature is preferably 300°C to 1000°C, more preferably 400°C to 800°C, and particularly preferably 450°C to 700°C. A specific example of the firing time is preferably 1 hour to 10 hours. When the firing temperature is 700°C or lower, it is preferable to set the firing atmosphere to an oxidizing atmosphere or an air atmosphere. This allows Al oxides and Bi oxides to be appropriately generated on the surface of the abrasive grains 12 during firing. On the other hand, when the firing temperature exceeds 700°C, it is preferable to set the atmosphere to a non-oxidizing atmosphere. This prevents oxidation of the abrasive grains (diamond, etc.).

3. Vitrified Grindstone Next, a description will be given of the manufactured vitrified grindstone 100. Fig. 3 is a diagram showing a schematic diagram of the vitrified grindstone according to this embodiment.

The vitrified grinding wheel 100 shown in FIG. 3 includes a plurality of abrasive materials 10 (abrasive grains 12 and an Al-Bi coating 14) and a vitrified bond 20 that bonds the plurality of abrasive materials 10. Specifically, the vitrified grinding wheel 100 has a bond network in which a plurality of abrasive grains 12 are bonded via the vitrified bond 20. The vitrified grinding wheel 100 may be a porous body having a plurality of voids 30. As described above, the voids 30 function as spaces that temporarily store grinding chips generated when a workpiece is ground.

The vitrified grinding wheel 100 in this embodiment contains an abrasive material 10 having an Al-Bi coating 14, so that Al oxides and Bi oxides are generated on the surface of the abrasive grains 12 during the manufacturing process. These oxides have good wettability with the vitrified bond 20, so a network of the vitrified bond 20 between the abrasive grains 12 is suitably formed. This allows the vitrified grinding wheel 100 to exhibit excellent strength.

In addition, some or all of the oxides originating from the Al-Bi coating 14 may be incorporated into the vitrified bond 20 during the wheel manufacturing process. This may result in an Al-Bi region 22 that contains more Al and Bi than other regions (intermediate region 24) near the surface of the abrasive grain 12. This Al-Bi region 22 is formed by solidification of glass that incorporates oxides originating from the Al-Bi coating 12 of the abrasive material 10. The vitrified wheel 100 having such a configuration has superior strength because the abrasive grain 12 and the intermediate region 24 are firmly bonded via the Al-Bi region 22. Note that the formation of this Al-Bi region 22 is not an essential component of the vitrified abrasive grain disclosed herein. For example, as shown in FIG. 3, the Al-Bi coating 14 may remain in the vitrified abrasive grain 100 after manufacturing. As described above, even if the Al-Bi coating 14 is not incorporated into the vitrified bond 20 (glass), it can improve the wettability between the abrasive 10 and the vitrified bond 20, thereby contributing to improving the strength of the vitrified grinding wheel 100.

The thickness of the Al-Bi region 22 is preferably 0.005 μm or more, more preferably 0.01 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.5 μm or more. By forming an Al-Bi region 22 of such a sufficient thickness, the above-mentioned strength improvement effect can be adequately exhibited. On the other hand, the thickness of the Al-Bi region 22 is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 2 μm or less, and particularly preferably 1 μm or less. This makes it possible to suppress a reduction in the strength improvement effect caused by the oxides derived from the Al-Bi coating 12 diffusing over a wide area.

The ratio of the total number of Al and Bi atoms to the total number of metal elements and metalloid elements in the Al-Bi region 22 (hereinafter also referred to as the "Al-Bi content X of the Al-Bi region 22") can be 30% or more (preferably 30% to 90%, more preferably 40% to 80%, and particularly preferably 50% to 70%). The vitrified bond 20 (Al-Bi region 22) containing a large amount of Al and Bi elements is strongly bonded to the abrasive grains 12, so that the strength of the vitrified grinding wheel 100 can be more preferably improved. The constituent elements of the Al-Bi region can be measured by selecting any abrasive grain from a cross-sectional SEM image (or TEM image) of the vitrified grinding wheel and analyzing the vitrified bond present in the region up to 0.1 μm from the surface of the abrasive grain using energy dispersive X-ray analysis (EDX analysis). Additionally, the above "Al-Bi content X in the Al-Bi region" is the average value for 100 abrasive grains.

In addition, the vitrified grinding wheel 100 according to this embodiment preferably has a ratio (X/Y) of the Al-Bi content X of the Al-Bi region 22 to the Al-Bi content Y of the intermediate region 24 of 1.1 or more (preferably 1.2 to 5, particularly preferably 1.5 to 3). The vitrified grinding wheel 100 that satisfies such conditions has particularly excellent strength because the diffusion of Al oxides and Bi oxides during firing is suppressed and glass with excellent fluidity and fixation remains in the vicinity of the abrasive grains 12. The constituent elements of the intermediate region can be measured by arbitrarily selecting a 1 μm square region 5 μm or more away from the surface of the abrasive grain in a cross-sectional SEM image (or TEM image) of the vitrified grinding wheel and analyzing the constituent elements of the region using energy dispersive X-ray analysis (EDX analysis). The above-mentioned "Al-Bi content Y of the intermediate region" is the average value of 100 measurement regions.

The vitrified grinding wheel 100 according to this embodiment can be used to grind workpieces of various materials and shapes. The material of the workpiece can be, for example, metal or semimetallic materials such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, 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 be made of a plurality of these materials. In particular, it is suitable for grinding workpieces made of metal materials or semiconductor materials. The vitrified grinding wheel disclosed herein has high abrasive grain retention and improved durability, and can therefore be used suitably for high-load grinding such as ultra-high-speed grinding.

The above describes one embodiment of the technology disclosed herein. However, the above-described embodiment is not intended to limit the technology disclosed herein. In other words, the technology disclosed herein may include various modifications of the above-described embodiment.

[Test Example]
Next, test examples related to the technology disclosed herein will be described. Note that the technology disclosed herein is not limited to the following test examples.

First Test
In this test, as a preliminary test, five types of coating materials for abrasive grains (coating materials A to E) were formed, and the wettability of each coating material with respect to the vitrified bond was evaluated.

1. Preparation of coating material (1) Coating material A
First, Al resinate (Kawaken Fine Chemicals aluminum ethyl acetoacetate diisopropylate: ALCH, Al ₂ O ₃ equivalent: 18.4 wt %) and Bi resinate (Bi ₂ O ₃ equivalent: 13.1 wt %) were dissolved in 20 ml of ethanol. At this time, the amount of Al resinate and Bi resinate added was adjusted so that the total amount of Al ₂ O ₃ and Bi ₂ O ₃ after firing was 0.1 g in oxide equivalent. In addition, in the coating material A, the ratio of Al resinate to Bi resinate was adjusted so that Al/(Al+Bi) was 0.2. Then, this coating material was applied to an alumina substrate and dried, and then fired in the air (500°C, 0.5 hours). As a result, an Al-Bi coating was formed on the surface of the alumina substrate.

(2) Coating material B
In forming coating material B, an Al--Bi coating was formed on the surface of an alumina substrate following the same procedure as for coating material A, except that Al/(Al+Bi) was changed to 0.5.

(3) Coating material C
In forming coating material C, an Al--Bi coating was formed on the surface of an alumina substrate following the same procedure as for coating material A, except that Al/(Al+Bi) was changed to 0.8.

(4) Coating material D
Coating material D was formed by following the same procedure as for coating material A, except that only Al resinate was used (Al/(Al+Bi)=1), to form an Al coating on the surface of an alumina substrate.

(5) Coating material E
In forming coating material E, a Bi coat was formed on the surface of an alumina substrate following the same procedure as for coating material A, except that only Bi resinate was used (Al/(Al+Bi)=0).

2. Evaluation Test In this test, a dispersion liquid was prepared by dispersing vitrified bond powder (TOMATEC Corporation TMX-501F _Bi2O3 - _ZnO - _{B2O3 -} SiO2 _- based glass) in alcohol. The dispersant was then dropped onto the coating material, which was then dried and then fired in the air (570°C, 2 hours). The surface of the fired coating material was then observed with an FE-SEM. FE-SEM photographs of coating materials A to E are shown in Figures 4 to 8.

First, as shown in Figures 7 and 8, in coating materials D and E, the majority of the vitrified bond after firing was present in a spherical shape on the coating material. This showed that Al coating or Bi coating alone did not provide sufficient wettability to the vitrified bond during firing. On the other hand, as shown in Figures 4 to 6, in coating materials A to C, the vitrified bond was wet and spread out compared to coating materials D and E. This showed that Al-Bi coatings, which contain both Al and Bi, are excellent in terms of improving the wettability of the vitrified bond during firing. In particular, in coating materials B and C, almost no spherically repelled vitrified bond was observed.

<Second test>
Next, in this test, vitrified grinding wheels were manufactured using abrasive grains to which coating materials A to E were attached.

1. Sample preparation (1) Test example 1
First, 9.9 g of diamond abrasive grains (FRM4-6, manufactured by Global Diamond Co., Ltd.) were weighed. Then, the abrasive grains were dispersed in a coating solution (solvent: ethanol) containing coating material A (Al/(Al+Bi)=0.2). Then, the coating solution was dropped onto a film placed on a hot plate at 80°C to obtain a dry powder. Next, the dry powder was crushed in a mortar and then fired in an air atmosphere (temperature: 600°C, heating rate: 10°C/min, time: 30 minutes). This resulted in an abrasive material with a metal oxide Al-Bi coating attached to the surface of the abrasive grains.

(2) Test Example 2
In Test Example 2, an abrasive was obtained in the same manner as in Test Example 1, except that the coating material was changed to coating material B (Al/(Al+Bi)=0.5).

(3) Test Example 3
In Test Example 3, an abrasive was obtained in the same manner as in Test Example 1, except that the coating material was changed to coating material C (Al/(Al+Bi)=0.8).

(4) Test Example 4
In Test Example 4, an abrasive was obtained in the same manner as in Test Example 2, except that the dried powder after crushing was not subjected to a firing treatment. That is, in Test Example 4, an abrasive was produced in which an Al-Bi coating of an organometallic compound (resinate) was attached to the surface of the abrasive grains.

(5) Test Example 5
In Test Example 5, an abrasive was obtained in the same manner as in Test Example 1, except that the coating material was changed to Coating Material D (Al coating: Al/(Al+Bi)=1).

(6) Test Example 6
In Test Example 6, an abrasive was obtained in the same manner as in Test Example 1, except that the coating material was changed to Coating Material E (Bi coating: Al/(Al+Bi)=0).

(7) Test Example 7
In Test Example 6, the abrasive was obtained in the same manner as in Test Example 1, except that the abrasive was dispersed in ethanol not containing a coating material. That is, in Test Example 7, no coating material was attached to the surface of the abrasive.

2. Evaluation test (1) Preparation of vitrified grinding stone Abrasive (Test examples 1 to 7), vitrified bond powder (TOMATEC Co., Ltd. TMX-501F Bi ₂ O ₃ -ZnO-B ₂ O ₃ -SiO _2- based glass), pore former (Sekisui Chemical Co., Ltd. Technopolymer, MB30X-8Y), and binder (Kyoeisha Kagaku Co., Ltd. Oricox, #2435E) were mixed to prepare a clay. The amount of abrasive added was set to 8.12g, and the amount of vitrified bond added was set to 7.89g. The amount of pore former added was set to 1.97g, and the amount of binder added was set to 3.03g. In the preparation of the clay, the materials were mixed until a paste was formed using a mixer (Awatori Rentaro, AR-550L-2). The clay was then dried at 100°C for 4 hours and crushed using a mortar to obtain a grindstone clay. Next, 3.0 g of the grindstone clay was press molded to produce a molded body (length: 55 mm, width: 6.5 mm, thickness: 4 mm). The molded body was fired in an air atmosphere to produce a vitrified grindstone for testing. The firing conditions were set to raise the temperature to 400°C over 5 hours, hold the temperature at 400°C for 2 hours, raise the temperature to 570°C over 1 hour and 40 minutes, and hold the temperature at 570°C for 2 hours. The fired molded body was then cooled for 4 hours or more.

(1) Measurement of three-point bending strength A three-point bending strength test was performed on the test grindstones of each example using an EZ-test made by Shimadzu Corporation. In this test, the distance L between the supports of the support for fixing the grindstone test pieces was set to 30 mm. The pressure application speed during the test was set to 0.5 mm/min. The results are shown in Table 1. The three-point bending strength (MPa) in Table 1 is the arithmetic average value of the three-point bending strength of five test grindstones.

As shown in Table 1, the three-point bending strength of Test Examples 1 to 4 was significantly improved compared to Test Examples 5 to 7. This is believed to be due to the formation of a strong bond network in the vitrified grinding wheel after firing. In addition, there was almost no change in the three-point bending strength between Test Examples 2 and 4. This shows that the Al-Bi coating exhibits a favorable strength-improving effect in both the metal oxide and organometallic compound (resinate) forms. This is believed to be due to the fact that the organometallic compound Al-Bi coating changes to Al oxide and Bi oxide in the early stages of the firing process, becoming in the same state as the metal oxide Al-Bi coating.

The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above. In other words, the technology disclosed herein includes the forms described in items 1 to 7 below.

<Item 1>
An abrasive material used in the manufacture of vitrified grinding wheels,
Abrasive grains and
a coating material attached to at least a portion of the surface of the abrasive grain;
Including,
The abrasive, wherein the coating material is an Al--Bi coating containing at least Al and Bi.

<Item 2>
2. The abrasive of claim 1, wherein the Al-Bi coating is a metal oxide or an organometallic compound.

<Item 3>
3. The abrasive according to item 1 or 2, wherein a ratio (Al/Al+Bi) of the number of moles of Al to the total number of moles of Al and Bi in the Al-Bi coat is 0.1 or more and 0.9 or less.

<Item 4>
The abrasive material according to any one of items 1 to 3, wherein the abrasive grains include one selected from the group consisting of diamond abrasive grains and cubic boron nitride abrasive grains.

<Item 5>
A plurality of abrasives;
a vitrified bond that bonds the plurality of abrasives;
Including,
The abrasive material is a vitrified grinding wheel according to any one of items 1 to 4.

<Item 6>
6. The vitrified grinding wheel according to item 5, wherein the vitrified bond has an Al-Bi region near the surface of the abrasive grains, the Al-Bi region containing more Al and Bi than other regions.

<Item 7>
Item 7. The vitrified grinding wheel according to item 5 or 6, wherein, when an elemental analysis based on energy dispersive X-ray analysis is performed on a cross-sectional microscope image, a ratio of a total number of atoms of the Al and the Bi to a total number of atoms of metal elements and metalloid elements in the Al-Bi region is 30% or more.

<Item 8>
8. The vitrified grinding wheel according to any one of items 5 to 7, wherein the vitrified bond is a glass material containing Bi.

10 Abrasive material 12 Abrasive grain 14 Al-Bi coating 20 Vitrified bond 22 Al-Bi region 24 Intermediate region 30 Gap 100 Vitrified grinding wheel

Claims (8)

An abrasive material used in the manufacture of vitrified grinding wheels,
Abrasive grains and
a coating material attached to at least a portion of the surface of the abrasive grain;
Including,
The abrasive, wherein the coating material is an Al--Bi coating containing at least Al and Bi. The abrasive material according to claim 1, wherein the Al-Bi coating is a metal oxide or an organometallic compound. The abrasive material according to claim 1 or 2, wherein the ratio of the number of moles of Al to the total number of moles of Al and Bi in the Al-Bi coating (Al/Al+Bi) is 0.1 or more and 0.9 or less. The abrasive material according to claim 1 or 2, wherein the abrasive grains include one selected from the group consisting of diamond abrasive grains and cubic boron nitride abrasive grains. A plurality of abrasives;
a vitrified bond that bonds the plurality of abrasives;
Including,
The abrasive material is the abrasive material according to claim 1 , in a vitrified grinding wheel. The vitrified grinding wheel according to claim 5, wherein the vitrified bond has an Al-Bi region near the surface of the abrasive grains that contains more Al and Bi than other regions. The vitrified grinding wheel according to claim 5 or 6, in which, when an elemental analysis based on energy dispersive X-ray analysis is performed on a cross-sectional microscope image, the ratio of the total number of atoms of the Al and the Bi to the total number of atoms of metal elements and metalloid elements in the Al-Bi region is 30% or more. The vitrified grinding wheel according to claim 5 or 6, wherein the vitrified bond is a glass material containing Bi.

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