JP7239951B1 - Stick grindstone and polishing method - Google Patents

Abstract

An object of the present invention is to provide a stick grindstone capable of improving the surface roughness and wear resistance of a surface to be polished of a work. A stick grindstone (10) presses a tip portion (17) against a surface (S) to be polished of a work (W) to grind the surface (S) to be polished. The stick grindstone 10 includes inorganic long fibers 15 and resin impregnated into the inorganic long fibers 15 and hardened. The inorganic long fibers 15 comprise 80 to 90% by weight of alumina component and 20 to 10% by weight of silica component. The crystal structure of the inorganic long fibers 15 includes mullite crystals and intermediate alumina. The average grain size of mullite crystals is smaller than 25 nm. [Selection drawing] Fig. 1

Description

The present invention relates to stick grindstones. The present invention also relates to a polishing method using a stick grindstone.

A rod-shaped stick grindstone obtained by impregnating and hardening a bundle of collective threads of inorganic long fibers with a resin is described in Patent Document 1. The stick grindstone disclosed in the same document is used for polishing molds. The stick grindstone has a rectangular or circular cross section and has elasticity to bend in a direction intersecting its axis. The aggregate yarn of inorganic long fibers extends in the axial direction of the stick grindstone, and the cross section of the aggregate yarn is exposed on the tip surface of the stick grindstone.

In Patent Literature 1, when polishing a surface to be polished of a work, the base of the stick grindstone is held by a tool holder. Also, the tool holder is connected to the spindle of the machine tool, and the spindle is rotated to press the tip surface of the stick grindstone against the surface to be polished of the work. Here, the tool holder converts rotation of the spindle into axial linear reciprocating and rotary motion of the spindle. Therefore, the tip of the stick grindstone is intermittently pressed against the work to polish the surface to be polished. Also, the tip of the stick grindstone contacts the work in a rotating state to grind the surface to be ground.

The abrasive material used for the grindstone is described in Patent Document 2. The abrasive material of the document consists of inorganic long fibers impregnated with resin. The inorganic long fibers comprise an alumina component of 80-90% by weight and a silica component of 20-10% by weight. The crystal structure of inorganic long fibers comprises mullite crystals and intermediate alumina. The average grain size of mullite crystals is 25 nm to 70 nm. In the abrasive material of the document, the inorganic long fibers contain 80% by weight or more of the alumina component, so the hardness of the inorganic long fibers is high. Further, since the average grain size of the mullite crystals is 25 nm or more, the grinding force for polishing and grinding the workpiece is large.

Patent Literature 2 describes a rectangular parallelepiped grindstone made of the above abrasive material. When polishing a work, the entire longitudinally extending side surface of the whetstone is pressed against the surface to be polished of the work. Further, the whetstone is reciprocated along the surface to be polished.

Japanese Patent No. 6832555 JP-A-10-183427

If the abrasive material for the grindstone described in Patent Document 2 is formed into a stick shape to form a stick grindstone, the stick grindstone can have sufficient grinding power. However, with the recent refinement of molds, it may not be possible to obtain a desired surface roughness by polishing with a stick grindstone made of an abrasive material for a grindstone described in Patent Document 2. In addition, the inventors have made extensive studies and found that the stick grindstone made of the abrasive material for a grindstone described in Patent Document 2 has room for improvement in the wear resistance of the stick grindstone.

SUMMARY OF THE INVENTION In view of the foregoing, an object of the present invention is to provide a stick grindstone capable of improving the surface roughness and wear resistance of the surface to be polished of the work. Another object of the present invention is to propose a polishing method using such a stick grindstone.

As a result of extensive studies, the present inventors have found that the inorganic long fibers comprise 80 to 90% by weight of alumina component and 20 to 10% by weight of silica component, and the crystal structure of the inorganic long fibers comprises intermediate alumina and mullite. When the material is used for a stick grindstone, it was found that the larger the crystallite of the mullite crystal in the crystal structure, the more easily scratches (polishing flaws) are generated on the surface of the workpiece to be polished.

In addition, as a result of extensive studies, the present inventors have found that the inorganic long fibers comprise 80 to 90% by weight of alumina component and 20 to 10% by weight of silica component, and the crystal structure of the inorganic long fibers is composed of intermediate alumina and mullite. The present inventors have found that when the provided abrasive material is used in a stick grindstone, the larger the crystallite of the mullite crystal in the crystal structure, the more the wear resistance of the stick grindstone is affected. In other words, mullite formation is progressing in inorganic long fibers having large crystallites. As the mullitization progresses, the inorganic long fibers become brittle. Here, when polishing a surface to be polished of a work using a rod-shaped stick grindstone using inorganic long fibers, the tip of the stick grindstone is pressed against the surface to be polished. In addition, since the rod-shaped stick grindstone has elasticity to flex in the direction intersecting the axis, when the tip is pressed against the workpiece, the stick grindstone hardly bounces on the surface to be polished or chattering occurs. It is also less likely that the stick grindstone will break or break. Therefore, when the tip of the stick grindstone is pressed against the surface to be polished, it is pressed with a relatively large pressing force in consideration of its elasticity to ensure a desired grinding force. For this reason, a load is likely to be applied to the tip of the stick grindstone, and if the inorganic long fibers exposed on the tip surface are mulliteized, the inorganic long fibers become brittle and crumble and wear easily.

On the other hand, the inventors of the present invention have found that when a stick grindstone uses an abrasive material in which the inorganic long fibers have an alumina component of 80 to 90% by weight and a silica component of 20 to 10% by weight, the mullite crystals are 25 nm. I got the knowledge that the grinding power of the stick grindstone can be secured even if it is smaller than. That is, if the inorganic long fibers contain 80% by weight or more of the alumina component, the hardness of the stick grindstone can be ensured. In addition, if the mullite crystals are smaller than 25 nm, mullite formation is suppressed in the inorganic long fibers, so embrittlement of the inorganic long fibers is suppressed. As a result, when the tip of the stick grindstone is pressed against the work and the surface to be polished is being polished, the inorganic long fibers are prevented from becoming brittle and crumble, and the inorganic long fibers bite into the work. Furthermore, when polishing and grinding a work with a rod-shaped stick grindstone, unlike the case where the entire side surface extending in the longitudinal direction is brought into contact with the surface to be polished like a rectangular parallelepiped grindstone, the work is polished. The tip can be pressed against the surface to be polished with a pressing force that takes into account the elasticity of the tip. Therefore, the stick grindstone can be provided with a predetermined grinding force. The present invention is based on these findings.

Ｄ_ｈｋｌ：（２１０）面の平均粒径
λ：Ｘ線の波長
θ：Ｘ線の視斜角
β_１／２：Ｘ線回折による結晶構造２θが２６°付近に現れるムライトの（２１０）面の回折線の半値幅 In order to solve the above-mentioned problems, the present invention provides a rod-shaped stick grindstone that grinds the target surface of a workpiece by pressing the tip thereof against the target surface to be ground, in which a plurality of inorganic long fibers extending in the axial direction; and a resin impregnated and solidified into inorganic long fibers, wherein a cross section of the inorganic long fibers is exposed on a tip surface, and has elasticity to bend in a direction intersecting with the axial direction, and the inorganic long fibers are made of alumina. 80 to 90% by weight of a component and 20 to 10% by weight of a silica component, the crystal structure of the inorganic long fibers comprises mullite crystals and intermediate alumina, and the average grain size of the mullite crystals is 25 nm. In the diffraction chart obtained by irradiating the inorganic long fibers with X-rays, a peak of the diffraction line of the (110) plane of mullite appears, and the average grain size of the mullite crystals is based on the diffraction chart. is calculated by the following formula.

D _hkl : Average grain size of the (210) plane λ: X-ray wavelength θ: X-ray glancing angle β _1/2 : The (210) plane of mullite whose crystal structure 2θ appears around 26° by X-ray diffraction half width of diffraction line

In the stick grindstone of the present invention, the average grain size of mullite crystals is smaller than 25 nm in the crystal structure of the inorganic long fibers. As a result, it is possible to suppress the occurrence of scratches (polishing flaws) on the polishing target surface of the work due to the size of the mullite crystals. Therefore, the surface roughness of the surface to be polished can be improved. Further, in the stick grindstone of the present invention, in the crystal structure of the inorganic long fibers, the average grain size of the mullite crystals is smaller than 25 nm. As a result, the embrittlement of the inorganic long fibers can be suppressed, so that when polishing is performed by pressing the tip of the stick grindstone, in which the cross section of the inorganic long fibers is exposed on the tip surface, against the surface to be polished of the workpiece, the inorganic long fibers become brittle. You can prevent it from collapsing. Therefore, the wear resistance of the stick grindstone is improved.

On the other hand, since the inorganic long fiber has an alumina component of 80% by weight or more, its hardness is ensured. Also, if the mullite crystals are small, embrittlement of the inorganic long fibers can be suppressed. Therefore, when the tip of the stick grindstone is pressed against the surface to be polished of the work for polishing, the inorganic long fibers are prevented from becoming brittle and crumble, and the inorganic long fibers bite into the work. Furthermore, when polishing or grinding a work with a rod-shaped stick grindstone, unlike the case where the entire side surface extending in the longitudinal direction is brought into contact with the surface to be polished as in the case of a rectangular parallelepiped grindstone, the tip of the work is polished. can be pressed against the surface to be polished. In addition, since the rod-shaped stick grindstone has elasticity that bends in a direction intersecting its axis, even when the tip is pressed against the surface to be polished, the stick grindstone bounces on the surface to be polished and chattering occurs. It is less likely that the stick grindstone will break or break. Therefore, a desired grinding force can be obtained by pressing the tip of the stick grindstone against the surface to be polished with a pressing force that takes into consideration the elasticity of the stick grindstone. Therefore, even if the average grain size of mullite crystals is 25 nm or less, the stick grindstone can ensure its grinding power.

In the present invention, the average grain size of the mullite crystals is desirably 20 nm or less. By doing so, it is easy to improve the surface roughness of the surface to be polished. Also, the wear resistance of the stick grindstone can be further improved.

In the present invention, it is desirable that the alumina component of the inorganic long fibers is 85% by weight or more. In this way, it is easy to increase the hardness of the inorganic long fibers. Therefore, it becomes easy to secure the grinding force of the stick grindstone.

In the present invention, the resin may be an epoxy resin.

In the present invention, the bending strength can be 500 MPa or more, and the bending elastic modulus can be 50 GPa or more. By doing so, it becomes easy to obtain a desired grinding force by increasing the pressing force for pressing the tip of the stick grindstone against the surface to be polished.

Next, the polishing method of the present invention is characterized in that the stick grindstone is mounted on a vibrating tool, and the tip of the stick grindstone is vibrated in the axial direction while being pressed against the surface to be polished of the work. The polishing method performed while pressing the tip portion of the stick grindstone against the surface to be polished of the work includes a polishing method performed while pressing the tip surface of the stick grindstone against the surface to be polished of the work.

Further, in the polishing method of the present invention, the above-described stick grindstone is attached to a vibration tool, and while pressing the tip of the stick grindstone against the surface to be polished of the work, the axial direction and the direction intersecting the axis of the stick grindstone. It is characterized by vibrating to. The polishing method performed while pressing the tip portion of the stick grindstone against the surface to be polished of the work includes a polishing method performed while pressing the tip surface of the stick grindstone against the surface to be polished of the work.

Further, in the polishing method of the present invention, the stick grindstone is mounted on a rotary tool, the tip of the stick grindstone is rotated while being pressed against the surface to be polished of the work, and the cross section of the stick grindstone is circular. characterized by being The polishing method performed while pressing the tip portion of the stick grindstone against the surface to be polished of the work includes a polishing method performed while pressing the tip surface of the stick grindstone against the surface to be polished of the work.

It is a perspective view of a stick grindstone. FIG. 2 is an explanatory view of a method of polishing a workpiece using the stick grindstone of FIG. 1; FIG. 2 is an explanatory diagram of another example of a method of polishing a workpiece using the stick grindstone of FIG. 1; It is a perspective view of a cylindrical stick grindstone. FIG. 5 is an explanatory view of a method of polishing a workpiece using the stick grindstone of FIG. 4; FIG. 5 is an explanatory diagram of another example of a method of polishing a workpiece using the stick grindstone of FIG. 4; It is a flowchart of the manufacturing method of a stick grindstone. 1 is a diffraction chart obtained by irradiating the inorganic long fibers of Example 1 with X-rays. 4 is a diffraction chart obtained by irradiating the inorganic long fibers of Comparative Example 1 with X-rays. 4 is a roughness curve of a surface to be polished of a workpiece polished by the stick grindstone of Example 1. FIG. 4 is a roughness curve of a surface to be polished of a workpiece polished by the stick grindstone of Comparative Example 1. FIG. It is a graph which shows the grinding amount of the workpiece|work after completion|finish of a comparison test. It is a graph of the wear amount of the stick grindstone after the end of the comparison test. 4 is a diffraction chart obtained by irradiating the inorganic long fibers of Example 2 with X-rays. 1 is a diffraction chart obtained by irradiating an inorganic long fiber of Reference Example with X-rays. 4 is a diffraction chart obtained by irradiating the inorganic long fibers of Comparative Example 2 with X-rays. 4 is a roughness curve of a surface to be polished of a workpiece polished by the stick grindstone of Example 2. FIG. It is a roughness curve of a surface to be polished of a work polished by a stick grindstone of a reference example. 3 is a roughness curve of a surface to be polished of a workpiece polished by the stick grindstone of Comparative Example 2. FIG. It is a graph which shows the grinding amount of the workpiece|work after completion|finish of a comparison test. It is a graph of the wear amount of the stick grindstone after the end of the comparison test.

A stick grindstone that is an embodiment of the present invention will be described below with reference to the drawings.

(stick whetstone)
FIG. 1 is a perspective view of a stick grindstone. FIG. 2 is an explanatory diagram of a method of polishing a workpiece using the stick grindstone of FIG. FIG. 3 is an explanatory diagram of another example of a method of polishing a workpiece using the stick grindstone of FIG. FIG. 4 is a perspective view of a cylindrical stick grindstone. FIG. 5 is an explanatory diagram of a method of polishing a workpiece using the stick grindstone of FIG. FIG. 6 is an explanatory diagram of another example of a method of polishing a workpiece using the stick grindstone of FIG.

As shown in FIG. 1, the stick grindstone 10 is rod-shaped and has a rectangular cross section. In this example, the stick grindstone 10 has a rectangular cross-section. The stick grindstone 10 includes a plurality of inorganic long fibers 15 extending in the axial direction along the axis L, and a resin 16 impregnated in the inorganic long fibers 15 and solidified. The inorganic long fibers 15 are polycrystalline fibers and contain 80 to 90% by weight of alumina component and 20 to 10% by weight of silica component. A cross section of the inorganic long fibers 15 is exposed on the tip surface 17 a of the stick grindstone 10 .

The stick grindstone 10 has elasticity to bend in a direction intersecting with the axis L thereof. The bending strength of the stick grindstone 10 is 500 MPa or more. The bending elasticity of the stick grindstone 10 is 50 GPa or more. More preferably, the stick grindstone 10 has a bending strength of 800 MPa or more and a bending elasticity of 65 GPa or more. In FIG. 1 and the like, the inorganic long fibers 15 are indicated by chain lines for convenience, but the inorganic long fibers 15 extend continuously from the tip end of the stick grindstone 10 to the base end side. In some cases, the plurality of inorganic long fibers 15 are inclined with respect to the axis L of the stick grindstone 10. In this case, the inclination angle is about 10°, and does not exceed 20° at maximum.

(polishing method)
As shown in FIG. 2, the stick grindstone 10 is used with its proximal end attached to the head of a hand-held vibration tool. The vibrating tool is, for example, an air vibrating tool or an ultrasonic vibrating tool. The vibration tool reciprocates (vibrates) the stick grindstone 10 attached to the head in the axial direction. The work W to be ground by the stick grindstone 10 is, for example, a mold for resin molding.

When polishing the work W, the tip 17 of the stick grindstone 10 is obliquely pressed against the surface S of the work W to be polished. That is, the stick grindstone 10 is pressed against the surface S to be polished in a posture in which the angle θ between the axis L and the surface S to be polished is an acute angle. In this example, the stick grindstone 10 has one long side of the rectangular cross section facing the surface S to be polished. Further, when polishing the work W, the stick grindstone 10 is pressed against the polishing target surface S of the work W from the direction along the axis L with a predetermined pressing force F. As shown in FIG. Further, the stick grindstone 10 is vibrated in the axial direction during polishing of the work W, as indicated by the arrow in FIG. When the vibration tool 11 is an air vibration tool, the air vibration tool vibrates the stick grindstone 10 at 5000 st/min or more. When the vibration tool 11 is an ultrasonic vibration tool, the ultrasonic vibration tool vibrates the stick grindstone 10 at 15 kHz or higher.

3, the stick grindstone 10 may polish the work W with its tip surface 17a pressed against the polishing target surface S of the work W in the vertical direction. In this case as well, the stick grindstone 10 is pressed against the surface S to be polished with the pressing force F from the direction along the axis L. As shown in FIG. 3, the stick grindstone 10 is vibrated in the axial direction by the vibrating tool 11. As shown in FIG. When the vibration tool 11 is an air vibration tool, the air vibration tool vibrates the stick grindstone 10 at 5000 st/min or more. When the vibration tool 11 is an ultrasonic vibration tool, the ultrasonic vibration tool vibrates the stick grindstone 10 at 15 kHz or higher.

Here, as indicated by solid line arrows and chain line arrows in FIG. Sometimes it is. In this case, the air vibration tool swings the stick grindstone 10 along an elliptical orbit during the stroke for vibrating the stick grindstone 10 in the axial direction, thereby realizing vibration in the axial direction and in a direction perpendicular to the axis L. . In this case, the air vibration tool vibrates the stick grindstone 10 at 5000 st/min or more.

In the case of using an air vibration tool, as shown in FIG. 2, even when polishing the workpiece W by pressing the tip 17 of the stick grindstone 10 obliquely against the surface S to be polished, the stick grindstone 10 is moved along the axis line. A direction and a direction perpendicular to the axis L may be vibrated.

Further, as shown in FIG. 5, the stick grindstone 10 may be used with its proximal end attached to the head of a hand-held rotary tool 11'. In this case, as shown in FIG. 4, a stick grindstone 10' having a circular cross section is desirable as the stick grindstone to be attached to the rotary tool 11'. That is, it is desirable to attach a cylindrical stick grindstone 10' to the rotary tool 11'. The rotating tool 11' is, for example, an electric rotating tool or an air rotating tool. As indicated by the solid arrow in FIG. 5, the rotary tool 11' rotates the stick grindstone 10' about its axis.

As shown in FIG. 5, when polishing the work W, the tip 17 of the stick grindstone 10' is obliquely pressed against the surface S of the work W to be polished. That is, the stick grindstone 10' is pressed against the surface S to be polished in a posture in which the angle θ between the axis L and the surface S to be polished is acute. Further, when polishing the work W, the stick grindstone 10' is pressed against the polishing target surface S of the work W from the direction along the axis L with a predetermined pressing force F. As shown in FIG. Furthermore, the stick grindstone 10' is rotated about the axis while the tip portion 17 is pressed against the surface S to be ground. The rotary tool 11' rotates the stick grindstone 10 at 100 rpm or more.

Here, even when the stick grindstone 10' is attached to the rotary tool 11' for grinding, the tip surface 17a of the stick grindstone 10' is perpendicular to the surface S of the workpiece W to be polished, as shown in FIG. It can be pressed and rotated. In this case as well, the stick grindstone 10' is pressed against the surface S to be polished with the pressing force F from the direction along the axis L. As shown in FIG. Further, the rotary tool 11' rotates the stick grindstone 10 at 100 rpm or more.

Here, in any of the above polishing methods, when polishing the target surface S of the workpiece with the stick grindstone 10, the pressing force F that presses the stick grindstone 10 against the target surface S and the side of the target surface S to be ground The stick grindstone 10 may bend in a direction intersecting its axis L due to a reaction force from the stick grindstone 10 or the like.

Note that the stick grindstones 10, 10' can also be used without being attached to a vibrating tool or the like. In this case, the operator presses the tip portion 17 of the stick grindstone 10, 10' against the polishing target surface S of the work W to perform manual polishing.

(Manufacturing method of stick grindstone)
FIG. 7 is a flow chart of the manufacturing method of the stick grindstone 10 . As shown in FIG. 7, the manufacturing method of the stick grindstone 10 includes a spinning step ST1, a calcination step ST2, a sintering step ST3, and a resin impregnation molding step ST4 in this order. In the spinning step ST1, a precursor fiber is obtained by dry-spinning an aqueous spinning dope consisting of basic aluminum chloride, colloidal silica and polyvinyl alcohol. In the calcination step ST2, the precursor fibers are sintered at a temperature of 900° C. or higher and 1300° C. or lower to obtain inorganic long fibers. In the sintering step ST3, the inorganic long fibers are heated at a high temperature of 1300° C. or higher for about 20 seconds. The heating temperature in the sintering step ST3 is higher than the heating temperature in the calcining step ST2.

In the resin impregnation molding step ST4, the inorganic long fibers are appropriately aligned to form a set yarn. In the resin impregnation molding step ST4, the set threads are impregnated with a thermosetting resin such as an epoxy resin or a phenol resin. Further, in the resin impregnation molding step ST4, the resin-impregnated set yarns are aligned to form a bundle of set yarns. Further, in the resin impregnation molding step ST4, the bundle of the bundled yarns impregnated with resin is pulled out so as to pass through a die having openings of a predetermined shape, and then passed through a heating furnace to be cured. After that, the bundle of set yarns with the cured resin is cut into a predetermined length. Thereby, a stick grindstone 10 having a predetermined length dimension and a predetermined cross-sectional shape is obtained.

A specific example of the manufacturing method is shown below. First, in the spinning step ST1, 34 kg of an aqueous solution of basic aluminum chloride containing 13.2% by weight of aluminum ions and 11.45% by weight of chloride ions, and 7.5 kg of colloidal silica containing 20% by weight of silicon dioxide are added to each other by average polymerization. 2.5 kg of partially saponified polyvinyl alcohol having a degree of 1700 is dissolved to prepare a spinning dope having a viscosity of about 1000 poise/20°C. Next, the spinning dope is extruded through a 1000-hole spinning nozzle for dry spinning. In the calcining step ST2, the spun inorganic filaments are calcined at 900° C. to 1300° C. to be ceramicized to obtain aggregate yarns. Thereafter, in the sintering step ST3, the set yarn is passed through a pipe furnace at 1300° C. to 1400° C. and continuously wound around a first bobbin under tension. At this time, the passing speed of the bundle yarn is adjusted so that the heating time is 20 seconds. Here, the set yarn is wound around a plurality of first bobbins.

In the resin impregnation molding step ST4, the set yarn is let out from each of the plurality of first bobbins and passed through a resin tank in which uncured resin is stored. In addition, the bundled threads impregnated with resin are pulled through a resin tank to form a bundle, which is then passed through a heating furnace.

The resin that impregnates the aggregate yarn and the bundle of aggregate yarn can have the following composition.
Epoxy resin (jER828, manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by weight Tetrahydromethyl phthalic anhydride (HN2200, manufactured by Hitachi Chemical Co., Ltd.) 85 parts by weight Imidazole (2E4MZ-CN, manufactured by Shikoku Kasei Co., Ltd.) 2 parts by weight

Here, in the resin impregnation molding step ST4, the bundle of bundled threads impregnated with resin passes through a die having an opening of a predetermined shape before reaching the heating furnace. As a result, the cross-sectional shape of the bundle of bundled yarns impregnated with the resin is made to correspond to the shape of the opening of the die. In addition, in the resin impregnation molding step ST4, the impregnated resin is cured by passing through a heating furnace. Therefore, the bundle of set yarns with the cured resin is cut into a predetermined size. As a result, when the opening of the die is rectangular, a stick grindstone having a predetermined length dimension and a rectangular cross section can be obtained. If the die opening is circular, a stick grindstone with a predetermined length dimension and a circular cross section is obtained.

(Example 1)
The stick grindstone 10 of Example 1 is rod-shaped and has a rectangular cross-sectional shape perpendicular to the axis L. As shown in FIG. The stick grindstone 10 has a thickness dimension (transverse dimension of the cross section) of 1 mm, a width dimension (longitudinal dimension of the cross section) of 4 mm, and a length dimension of 100 mm. The stick grindstone 10 has a bending strength of 1200 MPa and a bending elasticity of 115 GPa.

The stick grindstone 10 includes a plurality of inorganic long fibers 15 extending in the axial direction, and a resin 16 impregnating the inorganic long fibers 15 . The inorganic long fibers 15 comprise 85% by weight of alumina component and 15% by weight of silica component. The crystal structure of the inorganic long fibers 15 includes mullite crystals and intermediate alumina. The average grain size of crystal grains of mullite crystals is 20 nm. A cross section of the inorganic long fibers 15 is exposed on the tip surface 17 a of the stick grindstone 10 .

At the time of manufacturing the stick grindstone 10 of Example 1, the heating temperature in the calcination step ST2 is 1000.degree. The heating temperature in the sintering step ST3 is 1380°C. The heating time in the sintering step ST3 is 20 seconds.

Here, the crystal structure of the inorganic long fibers 15 was evaluated using X-ray diffraction. That is, after the sintering step ST3 and before the resin impregnation molding step ST4, the inorganic long fibers 15 were irradiated with X-rays and a diffraction chart was obtained. FIG. 8 is a diffraction chart when the inorganic long fibers 15 of Example 1 are irradiated with X-rays. Also, based on the diffraction chart, the average grain size of mullite crystals was calculated by the following general formula.

Ｄ_ｈｋl：（２１０）面の平均粒径
λ：Ｘ線の波長
θ：Ｘ線の視斜角
β_1/2：Ｘ線回折による結晶構造２θが２６°付近に現れるムライトの（２１０）面の回折線の半値幅

D _hkl : Average grain size of the (210) plane λ: X-ray wavelength θ: X-ray glancing angle β _1/2 : The (210) plane of mullite whose crystal structure 2θ appears around 26° by X-ray diffraction half width of diffraction line

The average grain size of the mullite crystals of the inorganic long fibers 15 from which the diffraction chart shown in FIG. 8 was obtained is D _hkl =20 (nm).

The diffraction line of the (210) plane of mullite has a lower peak as the grain size of the mullite crystal becomes smaller, and may be buried in other diffraction lines. For example, when the grain size of the mullite crystal is smaller than 25 nm, the peak of the diffraction line of the (210) plane of mullite may be buried in other diffraction lines, making it impossible to obtain the half-value width of the diffraction line. Therefore, the inventors have found by experiments that when the peak of the diffraction line of the (210) plane of mullite is buried in other diffraction lines and the half-value width of the diffraction line cannot be obtained, mullite can be obtained by using other measurement methods. It was confirmed that the average grain size of the crystals was 20 nm or less. Even if the peak of the diffraction line of the (210) plane of mullite is buried in other diffraction lines, if the peak of the diffraction line of the (110) plane of mullite appears in the diffraction chart, the crystal of the inorganic long fiber 15 The structure can be determined to have mullite crystals.

(Comparative example)
The stick grindstone of Comparative Example 1 is rod-shaped and has a rectangular cross-sectional shape perpendicular to the axis. The stick grindstone 10 has a thickness dimension (transverse dimension of the cross section) of 1 mm, a width dimension (longitudinal dimension of the cross section) of 4 mm, and a length dimension of 100 mm. The stick grindstone has a bending strength of 1200 MPa and a bending elasticity of 120 GPa. The stick grindstone of Comparative Example 1 includes a plurality of inorganic long fibers extending in the axial direction, and a resin impregnating the inorganic long fibers. The inorganic long fibers comprise an alumina component of 85% by weight and a silica component of 15% by weight. The crystal structure of inorganic long fibers comprises mullite crystals and intermediate alumina. On the tip surface of the stick grindstone of Comparative Example 1, the cross section of the inorganic long fibers is exposed.

FIG. 9 is a diffraction chart when the inorganic long fibers of Comparative Example 1 were irradiated with X-rays. In the diffraction chart shown in FIG. 9, the diffraction peak of the (210) plane of mullite clearly appears. The average grain size of the mullite crystals of the inorganic long fibers of Comparative Example 1 obtained based on the diffraction chart shown in FIG. 9 is D _hkl =35 (nm). That is, the average grain size of crystal grains of mullite crystals is 25 nm or more.

When manufacturing the stick grindstone of Comparative Example 1, the heating temperature in the calcination step ST2 was 1000°C. The heating temperature in the sintering step ST3 is 1390°C. The heating time in the sintering step ST3 is 30 seconds.

The heating temperature of the sintering step ST3 of Comparative Example 1 is higher than the heating temperature of the sintering step ST3 of Example 1. The heating time of the sintering step ST3 of Comparative Example 1 is also longer than the heating time of the sintering step ST3 of Example 1. As a result, the stick grindstone of Comparative Example 1 has mullite crystals with an average grain size of 25 nm or more in the crystal structure. Therefore, by controlling the heating temperature and heating time in the sintering step ST3 during the production of the stick grindstone, the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers can be controlled.

(comparison test)
A comparison test was conducted in which the grindstone stick 10 of Example 1 and the grindstone stick of Comparative Example 1 were used to grind a workpiece W. FIG. FIG. 10 is a roughness curve of the surface to be polished of the workpiece polished with the stick grindstone of Example 1. FIG. FIG. 11 is a roughness curve of the surface to be polished of the workpiece that was polished using the stick grindstone of Comparative Example 1. FIG. FIG. 12 is a graph showing the grinding amount of the workpiece after the completion of the comparative test in which the workpiece was ground using the stick grindstones of Example 1 and Comparative Example 1. FIG. FIG. 13 is a graph showing the amount of wear of the grindstone sticks after completion of a comparative test in which workpieces were ground using the grindstone sticks of Example 1 and Comparative Example 1. FIG.

In the comparative test, the base end portion of the stick grindstone 10 was attached to the head of a hand-held vibration tool 11 to grind the surface S of the workpiece W to be ground. The vibration tool is an air vibration tool. A workpiece W to be polished is a mold. The material of the work W is S50C (carbon steel for mechanical structure).

More specifically, as shown in FIG. 2, when polishing the workpiece W, the stick grindstone 10 of Example 1 and the stick grindstone of Comparative Example 1 were set so that the angle θ between the axis L and the surface S to be polished was 30°. The angle of the Further, the tip portion 17 of the grindstone stick 10 of Example 1 and the tip portion of the grindstone stick of Comparative Example 1 were pressed against the surface S to be polished with a pressing force F of 6N. Further, the stick grindstone 10 of Example 1 and the stick grindstone of Comparative Example 1 were vibrated at 21000 st/min in the axial direction by the vibrating tool 11 . Then, dry polishing of the workpiece W was continuously performed for 3 minutes on a polishing area of 30 mm×30 mm.

As can be seen from the graph of the work grinding amount after the comparative test shown in FIG.

In addition, the occurrence of scratches in the roughness curve of the surface to be polished of the workpiece when polished with the stick grindstone 10 of Example 1 shown in FIG. Fewer than the occurrence of scratches in the roughness curve of the surface to be polished. Furthermore, the surface roughness of the surface S to be polished of the work W when polished by the stick grindstone 10 of Example 1 is Rz 2.0 μm. The surface roughness of the surface S to be polished of the workpiece W after polishing with the stick grindstone of Comparative Example 1 was Rz 4.1 μm. Therefore, when the stick grindstone 10 of Example 1 is used for polishing, the surface roughness of the polishing target surface S of the work W can be improved.

Furthermore, from the graph of the wear amount of the stick grindstone after the comparative test shown in FIG. Therefore, the wear resistance of the grindstone stick 10 of Example 1 is better than that of the grindstone stick of Comparative Example 1.

(Effect)
In the stick grindstone 10 of this example, in the crystal structure of the inorganic long fibers 15, the average grain size of mullite crystals is smaller than 25 nm. As a result, it is possible to suppress the occurrence of scratches (polishing flaws) on the polishing target surface of the work due to the size of the mullite crystals. Therefore, the surface roughness of the surface to be polished can be improved.

Further, in the stick grindstone 10 of this example, in the crystal structure of the inorganic long fibers 15, the average grain size of the mullite crystals is smaller than 25 nm. As a result, embrittlement of the inorganic long fibers 15 can be suppressed, so that the inorganic long fibers 15 are prevented from being brittle and crumbling when the tip portion 17 of the stick grindstone 10 is pressed against the surface S to be polished of the workpiece W for polishing. can. Therefore, the wear resistance of the stick grindstone 10 is improved.

On the other hand, since the inorganic long fiber 15 contains 80% by weight or more of the alumina component, its hardness is ensured. Also, if the mullite crystals are small, embrittlement of the inorganic long fibers 15 can be suppressed. Therefore, when the tip portion 17 of the stick grindstone 10 is pressed against the surface S of the work W to be polished for polishing, the inorganic long fibers 15 are prevented from becoming brittle and crumble, and the inorganic long fibers 15 bite into the work W. In addition to this, the stick grindstone 10 is different from a rectangular parallelepiped grindstone in which the entire side surface is brought into contact with the surface to be polished of the work W, and the tip portion 17 is pressed against the surface to be polished of the work W to perform polishing. conduct. Further, since the grindstone stick 10 has elasticity to bend in the direction intersecting with the axis L, the tip portion 17 of the grindstone stick 10 can be pressed against the surface to be polished with a pressing force F considering the elasticity of the grindstone stick 10. can. Therefore, the stick grindstone 10 of Example 1 can secure grinding force even if the average grain size of the mullite crystals is smaller than 25 nm.

Here, it has been confirmed by experiments by the inventors that wear resistance of the stick grindstone 10 improves as the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 15 decreases.

Further, when the inorganic long fibers 15 contain 85% by weight or more of the alumina component, the hardness of the inorganic long fibers 15 can be increased compared to the case where the alumina component is lower than 85% by weight. Therefore, in order to ensure the polishing power of the stick grindstone 10, it is desirable to include 85% by weight or more of the alumina component. When the alumina component is 85% by weight or more, the silica component is 15% by weight or less.

Note that the inorganic long fibers 15 may contain other components in addition to the alumina component and the silica component. Even in this case, if the inorganic long fibers 15 contain 80 to 90% by weight of alumina component and 20 to 10% by weight of silica component, the grinding power of stick grindstone 10 can be ensured.

(Example 2, Reference Example, Comparative Example 2)
Next, stick grindstones 10 of Example 2, Reference Example, and Comparative Example 2 will be described. Similar to the grindstone stick 10 of Example 1, the grindstone sticks 10 of Example 2, Reference Example, and Comparative Example 2 consist of a plurality of inorganic long fibers 15 extending in the axial direction and a resin 16 impregnating the inorganic long fibers 15. And prepare. The inorganic long fibers 15 comprise 85% by weight of alumina component and 15% by weight of silica component. The crystal structure of the inorganic long fibers 15 includes mullite crystals and intermediate alumina. The cross section of the inorganic long fibers 15 is exposed on the tip surface 17a of the stick grindstone 10 of Example 2 and Reference Example.

Further, the grindstone sticks 10 of Example 2, Reference Example, and Comparative Example 2 have the same shape as the grindstone stick 10 of Example 1. That is, the stick grindstones 10 of Example 2, Reference Example, and Comparative Example 2 are bar-shaped and have a rectangular cross-sectional shape perpendicular to the axis L. As shown in FIG. Each stick grindstone 10 has a thickness of 1 mm, a width of 4 mm, and a length of 100 mm.

In Example 2, Reference Example, and Comparative Example 2, the crystal structure of the inorganic long fibers 15 was evaluated using X-ray diffraction in the same manner as in Example 1. That is, after the sintering step ST3 and before the resin impregnation molding step ST4, the inorganic long fibers 15 were irradiated with X-rays and a diffraction chart was obtained. FIG. 14 is a diffraction chart when the inorganic long fibers 15 of Example 2 were irradiated with X-rays. FIG. 15 is a diffraction chart when the inorganic long fibers 15 of the reference example are irradiated with X-rays. FIG. 16 is a diffraction chart when the inorganic long fibers 15 of Comparative Example 2 were irradiated with X-rays. As in Example 1, the average grain size of mullite crystals was calculated by a general formula based on a diffraction chart.

The average grain size of the mullite crystals of the inorganic long fibers 15 obtained from the diffraction chart of Example 2 shown in FIG. 14 is D _hkl =10 (nm). That is, the average grain size of the mullite crystal grains of the inorganic long fibers 15 in Example 2 is 10 nm. Here, the stick grindstone 10 of Example 2 has a bending strength of 1200 MPa and a bending elasticity of 112 GPa. When the stick grindstone 10 of Example 2 was manufactured, the heating temperature in the calcination step ST2 was 1000°C. The heating temperature in the sintering step ST3 is 1370°C. The heating time in the sintering step ST3 is 20 seconds.

The average grain size of the mullite crystals of the inorganic long fibers 15 obtained from the diffraction chart of the reference example shown in FIG. 15 is D _hkl =25 (nm). That is, the average grain size of the mullite crystal grains of the inorganic long fibers 15 in the reference example is 25 nm. Here, the stick grindstone 10 of the reference example has a bending strength of 1200 MPa and a bending elasticity of 116 GPa. At the time of manufacturing the stick grindstone 10 of the reference example, the heating temperature in the calcination step ST2 is 1000°C. The heating temperature in the sintering step ST3 is 1385°C. The heating time in the sintering step ST3 is 20 seconds.

The average grain size of the mullite crystals of the inorganic long fibers 15 obtained from the diffraction chart of Comparative Example 2 shown in FIG. 16 is D _hkl =30 (nm). That is, the average grain size of the mullite crystal grains of the inorganic long fibers 15 in Comparative Example 2 is 30 nm. Here, the stick grindstone 10 of Comparative Example 2 has a bending strength of 1200 MPa and a bending elasticity of 117 GPa. When the stick grindstone 10 of Comparative Example 2 was manufactured, the heating temperature in the calcination step ST2 was 1000°C. The heating temperature in the sintering step ST3 is 1390°C. The heating time in the sintering step ST3 is 20 seconds.

(comparison test)
Using the grindstone stick 10 of Example 2, the grindstone stick 10 of Reference Example, and the grindstone stick 10 of Comparative Example 2, a comparison test similar to the above comparison test was conducted. FIG. 17 is a roughness curve of the surface to be polished of the workpiece polished with the stick grindstone 10 of Example 2. FIG. FIG. 18 is a roughness curve of a surface to be polished of a work polished with the stick grindstone 10 of the reference example. FIG. 19 is a roughness curve of the surface to be polished of the workpiece polished with the stick grindstone 10 of Comparative Example 2. FIG. 17, 18 and 19, the horizontal axis is the measured length (mm) and the vertical axis is the height (μm).

FIG. 20 is a graph showing the grinding amount of the work after the comparison test in which the work was polished using each of the grindstone stick 10 of Example 2, the grindstone stick 10 of the reference example, and the grindstone stick 10 of the comparative example. FIG. 20 also shows the grinding amount of the stick grindstone 10 of Example 1 and the grinding amount of the stick grindstone 10 of Comparative Example 1 shown in FIG. FIG. 21 shows the second embodiment
1 is a graph of the amount of wear of the stick grindstone 10 after completion of a comparative test in which workpieces were ground using each of the stick grindstone 10 of No. 1, the stick grindstone 10 of the reference example, and the stick grindstone 10 of the comparative example. FIG. 21 also shows the wear amount of the stick grindstone 10 of Example 1 and the wear amount of the stick grindstone 10 of Comparative Example 1 shown in FIG.

As can _be seen from the graph of the _work grinding amount after the comparative test shown in FIG. ), and the grindstone stick 10 (D _hkl =25 (nm)) of the reference example are both the grindstone stick 10 of Comparative Example 1 (D _hkl =35 (nm)) and the grindstone stick 10 of Comparative Example 2 (D _hkl =30 (nm)). Specifically, the grinding amount of the stick grindstone 10 of Example 1 is 0.110 g. The grinding amount of the stick grindstone 10 of Example 2 is 0.109 g. The grinding amount of the stick grindstone 10 of the reference example is 0.111 g. The grinding amount of the stick grindstone 10 of Comparative Example 2 was 0.111 g. The grinding amount of the stick grindstone 10 of Comparative Example 2 was 0.111 g.

Further, from the _graph of the wear amount of the stick _grindstone 10 after the comparative test shown in FIG. (nm)) and the wear amount of the stick grindstone 10 (D _hkl =25 (nm)) of the reference example are the wear amount of the stick grindstone 10 (D _hkl =35 (nm)) of Comparative Example 1 and the comparison. It can be seen that the wear amount is smaller than that of the stick grindstone 10 (D _hkl =30 (nm)) of Example 2. Specifically, the wear amount of the stick grindstone 10 of Example 1 is 0.0029 g. The wear amount of the stick grindstone 10 of Example 2 is 0.0028 g. The wear amount of the stick grindstone 10 of the reference example is 0.0029 g. The wear amount of the stick grindstone 10 of Comparative Example 1 is 0.0046 g. The wear amount of the stick grindstone 10 of Comparative Example 2 is 0.0031. Here, the wear amount of the stick grindstone 10 of Example 1, Example 2, and Reference Example is less than 0.003 g, which is 35% or more lower than the wear amount of the stick grindstone of Comparative Example 1. .

Experiments by the inventors have confirmed that, in the crystal structure of the inorganic long fibers 15 of the stick grindstone 10, the smaller the average grain size of the mullite crystals, the more the abrasion loss of the stick grindstone 10 is reduced. That is, when the grain size of the mullite crystal is smaller than 10 nm, and the peak of the diffraction line of the (210) plane of mullite is buried in other diffraction lines, and an accurate grain size cannot be obtained, the wear amount of the tick grindstone 10 is , the amount of wear of the stick grindstone 10 of Example 2 is reduced. Therefore, the smaller the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 15, the more the wear resistance of the stick grindstone 10 improves.

Next, the surface of the polishing target surface S of the work W calculated based on the roughness curve (FIG. 17) of the polishing target surface of the work when polished by the stick grindstone 10 (Dhkl=10 (nm)) of Example 2 The roughness is Rz 2.04 μm. Further, the surface roughness of the surface S to be polished of the work W calculated based on the roughness curve (FIG. 18) of the surface to be polished of the work W when polished by the stick grindstone 10 (Dhkl=25 (nm)) of the reference example. is Rz 2.06 μm. The surface roughness of the surface S to be polished of the work W calculated based on the roughness curve (FIG. 10) of the surface to be polished of the work W when polished by the stick grindstone 10 (Dhkl=20 (nm)) of Example 1 is , Rz 2.05 μm. This value is between the surface roughness value obtained when a workpiece is polished by the stick grindstone 10 of Example 2 and the surface roughness value obtained when a workpiece is ground by the stick grindstone 10 of Reference Example.

In addition, the surface roughness of the polishing target surface S of the work W calculated based on the roughness curve ( FIG. 17 ) of the polishing target surface of the work W when polished by the stick grindstone 10 (Dhkl=30 (nm)) of Comparative Example 2 The height is Rz 2.17 μm. Furthermore, the stick grindstone 10 of Comparative Example 1 (Dh
kl=35 (nm)). Therefore, the smaller the average grain size of the mullite crystal grains of the inorganic long fibers 15, the more the occurrence of scratches is suppressed, and the surface roughness of the surface S to be polished of the workpiece W becomes smaller.

(Effect)
As supported by the above comparative test, in the stick grindstone 10, even if the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 15 is smaller than 25 nm, it is equivalent to the case where the average grain size of the mullite crystals is 25 nm or more. of grinding force can be obtained.

In addition, if the average grain size of mullite crystals in the crystal structure of the inorganic long fibers 15 of the stick grindstone 10 is reduced, the occurrence of scratches is suppressed, and the surface roughness of the polished surface S of the workpiece W after polishing is reduced. . Therefore, if the stick grindstone 10 in which the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 15 is smaller than 25 nm is used, compared to the case where the average grain size of the mullite crystals is 25 nm or more, the post-polishing work W is reduced. The surface roughness of the surface S to be polished can be reduced.

Furthermore, in the stick grindstone 10 in which the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 10 is smaller than 25 nm, the wear resistance of the stick grindstone 10 is higher than in the case where the average grain size of the mullite crystals is 25 nm or more. improves.

In the crystal structure of the inorganic long fibers 15, if the average grain size of the mullite crystals is 20 nm or less, the polishing target surface S of the work W after polishing is reduced compared to the case where the average grain size of the mullite crystals exceeds 20 nm. Surface roughness can be reduced. Further, if the average grain size of the mullite crystals in the crystal structure of the inorganic long fibers 15 is 20 nm or less, the abrasion resistance of the stick grindstone 10 is further improved compared to the case where the average grain size of the mullite crystals exceeds 20 nm. .

DESCRIPTION OF SYMBOLS 10... Stick grindstone, 11... Vibration tool, 15... Inorganic long fiber, 16... Resin, 17... Tip part, 17a... Tip surface, ST1... Spinning process, ST2... Calcination process, ST3... Sintering process, ST4... Resin Impregnation molding process

Claims (8)

A rod-shaped stick grindstone that polishes the surface to be polished by pressing the tip portion against the surface to be polished of the work,
comprising a plurality of inorganic long fibers extending in the axial direction and a resin impregnated and solidified in the inorganic long fibers,
The cross section of the inorganic long fiber is exposed on the tip surface,
Having elasticity to bend in a direction intersecting with the axial direction,
The inorganic long fibers have an alumina component of 80 to 90% by weight and a silica component of 20 to 10% by weight,
The crystal structure of the inorganic long fibers comprises mullite crystals and intermediate alumina,
The average grain size of the mullite crystals is smaller than 25 nm,
In the diffraction chart obtained by irradiating the inorganic long fibers with X-rays, a peak of the diffraction line of the (110) plane of mullite appears,
The stick grindstone, wherein the average grain size of the mullite crystals is calculated by the following formula based on the diffraction chart.

D _hkl : average grain size of (210) plane λ: wavelength of X-ray θ: glancing angle of X-ray β1/2: diffraction of (210) plane of mullite whose crystal structure 2θ appears in the vicinity of 26° by X-ray diffraction half width of line 2. The stick grindstone according to claim 1, wherein the mullite crystals have an average grain size of 20 nm or less. 2. The stick grindstone according to claim 1, wherein the alumina component of said inorganic long fibers is 85% by weight or more. The stick grindstone according to claim 1, wherein the resin is an epoxy resin. 2. The stick grindstone according to claim 1, which has a bending strength of 500 MPa or more and a bending elasticity of 50 GPa or more. Attaching the stick grindstone according to claim 1 to a vibration tool,
A polishing method comprising vibrating the tip of the stick grindstone in the axial direction while pressing the tip of the stick grindstone against the surface to be polished of the work. Attaching the stick grindstone according to claim 1 to a vibration tool,
A polishing method comprising vibrating the tip of the stick grindstone in the axial direction and in a direction intersecting the axis of the stick grindstone while pressing the tip of the stick grindstone against the surface to be polished of the work. Attaching the stick grindstone according to claim 1 to a rotary tool,
Rotate the tip of the stick grindstone while pressing it against the surface to be polished of the work,
A grinding method, wherein the stick grindstone has a circular cross section.

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