Grinding pin and polishing process

Abstract

A grinding pin (10) of Examples 1 and 2 polishes a surface (S) to be polished of a workpiece (W), with a distal end portion (17) pressed against the surface (S) to be polished. The grinding pin (10) of Examples 1 and 2 comprises inorganic filaments (15) and a resin (16) that impregnates and cures the inorganic filaments (15). The inorganic filaments (15) contain 80 to 90 weight percent of an alumina component and 20 to 10 weight percent of a silica component. The inorganic filaments (15) have a crystal structure containing the alumina intermediate, and the silica component is in an amorphous state. The inorganic filaments (15) have a BET specific area of ​​30 m 2 / g or less.

Description

Area

[0001] The present invention relates to a grinding pin. The present invention also relates to a polishing method using a grinding pin. background

[0002] Patent Literature 1 describes a rod-shaped grinding pin formed by impregnating and curing a bundle of inorganic filament yarn aggregates with a resin. The grinding pin in this literature is used for polishing molds. The grinding pin has a rectangular or circular cross section and is elastic enough to bend in a direction intersecting its axis. The inorganic filament yarn aggregates extend in the axial direction of the grinding pin, and the cross sections of the yarn aggregates are exposed at a distal end surface of the grinding pin.

[0003] In Patent Literature 1, when polishing a surface to be polished of a workpiece, the proximal portion of the grinding pin is held in a tool holder. The tool holder is connected to the spindle of a machine tool, and the spindle is rotated to press the distal end surface of the grinding pin against the surface to be polished of the workpiece. Here, the tool holder converts the spindle rotation into a linear reciprocating motion and a rotational motion in the axial direction of the spindle. Thus, the distal end portion of the grinding pin is intermittently pressed against the workpiece to polish the surface to be polished. The distal end portion of the grinding pin also comes into contact with the workpiece during rotation to polish the surface to be polished.

[0004] An abrasive material used for grinding stones is described in Patent Literature 2. The abrasive material in this literature consists of inorganic filaments impregnated with a resin. The inorganic filaments contain 80 to 90 weight percent of an alumina component and 20 to 10 weight percent of a silica component. The crystal structure of the inorganic filaments includes mullite crystals and the alumina intermediate. The mullite crystals have an average grain size of 25 nm to 70 nm. In the abrasive material in this literature, the hardness of the inorganic filaments is high because the inorganic filaments contain 80 weight percent or more of an alumina component. Since the mullite crystals have an average grain size of 25 nm or more, the grinding performance for polishing and grinding a workpiece is high.

[0005] Patent Literature 2 describes a rectangular grindstone made of the above-mentioned abrasive material. When polishing a workpiece, the grindstone is pressed with its entire longitudinal side surface against a surface of the workpiece to be polished. The grindstone is moved back and forth along the surface to be polished. List of citationsPatent literature Patent Literature 1: Japanese Patent No. 6832555 Patent Literature 2: Japanese Patent Application Publication No. H10-183427 SummaryTechnical problem

[0006] When the grinding material for grindstones described in Patent Literature 2 is formed into a rod shape to produce a grinding point, the grinding point can exhibit sufficient grinding performance. However, as the shapes have become increasingly precise in recent years, the grinding point made of the grinding material for grindstones described in Patent Literature 2 may not achieve the desired surface roughness during polishing. The inventors conducted extensive studies and found that the grinding point made of the grinding material for grindstones described in Patent Literature 2 has room for improvement in terms of abrasion resistance.

[0007] Against this background, an object of the present invention is to provide a grinding pin that can improve the surface roughness of a workpiece surface to be polished and improve the abrasion resistance. Another object is to provide a polishing method using such a grinding pin. Problem solving

[0008] The inventors of the present invention have conducted extensive studies and found that in a grinding pin using an abrasive material with inorganic filaments containing 80 to 90 wt% of an alumina component and 20 to 10 wt% of a silica component and having a crystal structure including the alumina intermediate and mullite, the larger the crystallites of the mullite crystals in the crystal structure, the greater the likelihood of scratches (polishing defects) on a surface to be polished of a workpiece.

[0009] As a result of extensive studies, the inventors also found that in a grinding pin using an abrasive material with inorganic filaments containing 80 to 90 wt. % of an alumina component and 20 to 10 wt. % of a silica component and having a crystal structure with the alumina intermediate and mullite, the larger the crystallites of the mullite crystals in the crystal structure, the more the cutting resistance of the grinding pin deteriorates. In other words, mullitization progresses in the inorganic filaments with large crystallites. As mullitization progresses, the inorganic filaments become brittle. Here, when a surface to be polished of a workpiece is polished with a rod-shaped grinding pin made of inorganic filaments, the distal end portion of the grinding pin is pressed against the surface to be polished.Because the grinding pin has the elasticity to bend in a direction crossing the axis, when the distal end portion is pressed against the workpiece, the grinding pin is less likely to bounce or flutter on the surface to be polished, and the grinding pin is less likely to be damaged or broken. Therefore, when the distal end portion of the grinding pin is pressed against a surface to be polished, it is pressed with a relatively large compressive force in view of its elasticity to ensure the desired grinding performance. As a result, the distal end portion of the grinding pin is often subjected to stress, and when the inorganic filaments exposed on the distal end surface are mullitized, the inorganic filaments become brittle and easily collapse and wear.

[0010] On the other hand, the inventors found that when a grinding pin uses an abrasive material containing inorganic filaments containing 80 to 90 weight percent of an alumina component and 20 to 10 weight percent of a silica component, the grinding performance of the grinding pin can be ensured even without mullite crystals if the inorganic filaments have a specific area of ​​a predetermined value or less. In other words, if the inorganic filaments contain 80 weight percent or more of an alumina component, the hardness of the grinding pin can be ensured. If the specific area of ​​the inorganic filaments is a predetermined value or less, it is possible to prevent or suppress the inorganic filaments from absorbing moisture from the air and inhibiting the curing of the resin impregnating the inorganic filaments.Furthermore, when the specific area of ​​the inorganic filaments is a predetermined value or less, the inorganic filaments have fewer pores and unevenness, and bubbles in the resin impregnating the inorganic filaments can be suppressed. Thus, the occurrence of resin impregnation failure due to bubbles can be prevented. As a result, brittle collapse of the inorganic filaments is suppressed when the distal end portion of the grinding pin is pressed against a workpiece to polish a surface to be polished, and the inorganic filaments engage the workpiece.Unlike a case where a workpiece is polished by bringing the entire longitudinal side surface into contact with a surface to be polished, as with a rectangular grindstone, when a workpiece is ground and polished with the rod-shaped grinding pin, the distal end portion can be pressed against the surface to be polished with a compressive force, taking into account the elasticity of the grinding pin. Thus, the grinding pin can have a predetermined grinding performance. The present invention is based on these findings.

[0011] To solve the above problem, the present invention provides a rod-shaped grinding pin whose distal end portion is pressed against a surface to be polished of a workpiece to polish the surface to be polished. The grinding pin includes a plurality of inorganic filaments extending in the axial direction and a resin impregnated and cured in the inorganic filaments. Cross sections of the inorganic filaments are exposed at a distal end surface of the grinding pin. The grinding pin is elastic to bend in a direction intersecting the axial direction. The inorganic filaments contain 80 to 90 wt. % of an alumina component and 20 to 10 wt. % of a silica component. The inorganic filaments have a crystal structure containing the alumina intermediate. The silica component is in an amorphous state.The inorganic filaments have a BET specific area of ​​28.7 m. 2 / g or less.

[0012] In the grinding pin according to the present invention, the silica component of the inorganic filaments is in an amorphous state. Therefore, the crystal structure of the inorganic filaments does not contain mullite crystals. This structure can prevent scratches (polishing defects) on the surface of a workpiece to be polished due to mullite crystals. This can improve the surface roughness of the surface to be polished. In the grinding pin according to the present invention, the silica component of the inorganic filaments is in an amorphous state. Thus, the inorganic filaments are not embrittled by mullitization. Furthermore, the inorganic filaments have a BET specific area of ​​28.7 m². 2 / g or less. The inorganic filaments with such a BET specific area have fewer pores and unevenness and therefore absorb less moisture. Thus, it is possible to prevent or suppress the inorganic filaments from absorbing moisture from the air and inhibiting the curing of the resin impregnating the inorganic filaments. Because the inorganic filaments with such a BET specific area have fewer pores and unevenness, it is possible to prevent or suppress resin impregnation failure in the grinding pin, which would otherwise be caused by bubbles remaining in the resin impregnating the inorganic filaments.As a result, embrittlement of the inorganic filaments and damage to the pin can be avoided, so that the abrasion resistance of the grinding pin is improved when the distal end portion of the grinding pin is pressed against a surface to be polished of a workpiece for polishing.

[0013] On the other hand, since the inorganic filaments contain 80% or more of an alumina component by weight, the hardness can be easily ensured. With the inorganic filaments, which have a BET specific area of ​​28.7 m 2 / g or less, it is possible to prevent embrittlement of the grinding pin, which is otherwise caused by moisture absorption that inhibits the curing of the resin. Furthermore, when the BET specific area is small, the grinding pin is less likely to be damaged due to a resin impregnation defect in the grinding pin, which would otherwise be caused by bubbles remaining in the resin impregnating the inorganic filaments. Therefore, when the distal end portion of the grinding pin is pressed against a surface of a workpiece to be polished for polishing, brittle collapse of the inorganic filaments and the grinding pin is prevented, and the inorganic filaments engage with the workpiece.Furthermore, unlike a case where the entire longitudinal side surface is brought into contact with a surface to be polished to polish a workpiece, such as a rectangular grindstone, when grinding and polishing a workpiece with the rod-shaped grinding pin, the distal end portion can be pressed against the surface to be polished to perform polishing. Since the rod-shaped grinding pin has the elasticity to bend in its axis-crossing direction, the grinding pin is less likely to bounce or flutter on the surface to be polished even when the distal end portion is pressed against the workpiece, and the grinding pin is less likely to be damaged or broken.Thus, the desired grinding performance can be achieved by pressing the distal end portion of the grinding pin against the surface to be polished with a compressive force that takes the elasticity of the grinding pin into account. The grinding pin can therefore ensure its grinding performance even if its crystal structure does not contain mullite crystals.

[0014] In the present invention, it is preferable that the inorganic filaments have a BET specific area of ​​12.5 m 2 / g or less. This configuration can improve the grinding performance of the grinding pin compared to a BET specific area greater than 12.5 m 2 / g. This configuration also improves the abrasion resistance compared to a BET specific area larger than 12.5 m 2 / G.

[0015] In the present invention, it is preferable that the inorganic filaments contain 85% or more of an alumina component. With this configuration, the hardness of the inorganic filaments can be easily increased. Thus, the grinding performance of the grinding pin can be easily ensured.

[0016] In the present invention, the resin may be epoxy resin.

[0017] In the present invention, the grinding pin may have a flexural strength of 500 MPa or more and a flexural elasticity of 50 GPa or more. With this configuration, the desired grinding performance can be easily achieved by increasing the pressing force with which the distal end portion of the grinding pin is pressed against a surface to be polished.

[0018] A polishing method according to the present invention includes: attaching the above-described grinding pin to a vibration tool; and vibrating a distal end portion of the grinding pin in the axial direction while pressing the distal end portion against a surface of a workpiece to be polished. The polishing process performed while pressing the distal end portion of the grinding pin against a surface of a workpiece to be polished includes a polishing process performed while pressing a distal end surface of the grinding pin against a surface of a workpiece to be polished.

[0019] A polishing method according to the present invention includes: attaching the above-described grinding pin to a vibration tool; and vibrating a distal end portion of the grinding pin in the axial direction and in a direction intersecting an axis of the grinding pin while pressing the distal end portion against a surface of a workpiece to be polished. The polishing process performed while pressing the distal end portion of the grinding pin against a surface of a workpiece to be polished includes a polishing process performed while pressing a distal end surface of the grinding pin against a surface of a workpiece to be polished.

[0020] In addition, a polishing method according to the present invention includes: attaching the abrasive pin described above to a rotating tool; and rotating a distal end portion of the abrasive pin that is pressed against a surface of a workpiece to be polished. The abrasive pin has a circular cross-section. The polishing method performed while the distal end portion of the abrasive pin is pressed against a surface of a workpiece to be polished includes a polishing method performed while a distal end surface of the abrasive pin is pressed against a surface of a workpiece to be polished. Brief Description of the Drawings Fig. 1 is a perspective view of an abrasive pin. Fig. 2 is a view of a method for polishing a workpiece using the abrasive pin in the Fig. 1. Fig. 3 is a diagram showing another example of the method for polishing a workpiece using the grinding pin in the Fig. 1. Fig. 4 is a perspective view of a cylindrical grinding pin. Fig. 5 is an illustration of a method for polishing a workpiece using the grinding pin in the Fig. 4. Fig. 6 is a diagram showing another example of the method for polishing a workpiece using the grinding pin in the Fig. 4. Fig. 7 is a flowchart of a method for manufacturing the grinding pin. Fig. Figure 8 is a diffraction pattern obtained by irradiating inorganic filaments in Example 1 with X-rays. Fig. 9 is a diffraction pattern obtained by irradiating inorganic filaments in Comparative Example 2 with X-rays. Fig. 10 is a roughness curve of a surface to be polished of a workpiece polished with the grinding pin of Example 1. Fig. 11 is a roughness curve of a surface to be polished of a workpiece polished with the grinding pin of Example 2. Fig. 12 is a roughness curve of a surface to be polished of a workpiece when a grinding pin of Comparative Example 1 is used. Fig. 13 is a roughness curve of a surface to be polished of a workpiece polished with a grinding pin of Comparative Example 2. Fig. Figure 14 is a graph showing the amount of grinding of a workpiece after a comparison test. Fig. Figure 15 is a graph showing the amount of removal of the grinding pin after the comparison test. Fig. 16 is a photograph of a side surface of the grinding pin of Example 2. Fig. 17 is a photograph of a side surface of the grinding pin of Comparative Example 1. Description of embodiments

[0021] A grinding pin according to embodiments of the present invention will be described below with reference to the drawings. (Grinding pin)

[0022] The Fig. 1 is a perspective view of a grinding pin. The Fig. 2 is an illustration of a method for polishing a workpiece using the grinding pin in the Fig. 1. The Fig. 3 is a diagram showing another example of the method for polishing a workpiece using the grinding pin in the Fig. 1. The Fig. 4 is a perspective view of a cylindrical grinding pin. The Fig. 5 is an illustration of a method for polishing a workpiece using the grinding pin in the Fig. 4. The Fig. 6 is a diagram showing another example of the method for polishing a workpiece using the grinding pin in the Fig. 4.

[0023] As in the Fig. 1, a grinding pin 10 is rod-shaped and has a rectangular cross-section. In this example, the grinding pin 10 has a rectangular cross-section. The grinding pin 10 includes a plurality of inorganic filaments 15 extending in the axial direction along its axis L, and a resin 16 that impregnates and solidifies the inorganic filaments 15. The inorganic filaments 15 are polycrystalline fibers and contain 80 to 90 weight percent of an alumina component and 20 to 10 weight percent of a silica component. Cross-sections of the inorganic filaments 15 are exposed at a distal end surface 17a of the grinding pin 10.

[0024] The grinding pin 10 is elastic to bend in a direction intersecting its axial direction L. The grinding pin 10 has a bending strength of 500 MPa or more. The grinding pin 10 has a bending elasticity of 50 GPa or more. More preferably, the grinding pin 10 has a bending strength of 800 MPa or more and the grinding pin 10 has a bending elasticity of 65 GPa or more. Although the inorganic filaments 15 are shown in the Fig. 1 and the like are shown by dashed lines, the inorganic filaments 15 extend continuously from the distal end to the proximal end of the grinding pin 10. A plurality of inorganic filaments 15 may be inclined with respect to the axis L of the grinding pin 10. In this case, however, the inclination angle is about 10° and does not exceed 20°. (polishing process)

[0025] As in the Fig. As shown in Figure 2, the grinding pin 10 is used with its proximal end portion attached to the head of a handheld vibrating tool. The vibrating tool is, for example, a pneumatic vibrating tool or an ultrasonic vibrating tool. The vibrating tool reciprocates (vibrates) the grinding pin 10 mounted on the head in the axial direction. A workpiece W to be polished with the grinding pin 10 is, for example, a mold for resin casting.

[0026] When polishing the workpiece W, the grinding pin 10 is pressed obliquely at its distal end portion 17 against a surface S of the workpiece W to be polished. In other words, the grinding pin 10 is pressed against the surface S to be polished in a posture in which the angle θ between its axis L and the surface S to be polished is an acute angle. In this example, one of the long sides of the rectangular cross section of the grinding pin 10 faces the surface S to be polished. When polishing the workpiece W, the grinding pin 10 is pressed with a predetermined pressing force F from a direction along the axis L against the surface S of the workpiece W to be polished. In addition, the grinding pin 10, as indicated by the arrow in the Fig. 2, vibrates in the axial direction when polishing the workpiece W. In a case where the vibration tool 11 is a pneumatic vibration tool, the pneumatic vibration tool vibrates the grinding pin 10 at 5000 h / min or more. In a case where the vibration tool 11 is an ultrasonic vibration tool, the ultrasonic vibration tool vibrates the grinding pin 10 at 15 kHz or more.

[0027] As in the Fig. 3, the grinding pin 10 can be pressed vertically at its distal end surface 17a against the surface S of the workpiece W to be polished in order to polish the workpiece W. In this case too, the grinding pin 10 is pressed against the surface S to be polished with a compressive force F from the direction along the axis L. As indicated by the solid arrow in the Fig. 3, the grinding pin 10 is vibrated in the axial direction by the vibration tool 11. In a case where the vibration tool 11 is a pneumatic vibration tool, the pneumatic vibration tool vibrates the grinding pin 10 at 5000 rpm or more. In a case where the vibration tool 11 is an ultrasonic vibration tool, the ultrasonic vibration tool vibrates the grinding pin 10 at 15 kHz or more.

[0028] Here, as indicated by the solid arrow and the chain arrow in the Fig. 2, in a case where a pneumatic vibration tool is used, the grinding pin 10 can be vibrated by the pneumatic vibration tool in the axial direction and in the direction orthogonal to the axis L. In this case, the pneumatic vibration tool oscillates the grinding pin 10 along an elliptical orbit during a stroke that vibrates the grinding pin 10 in the axial direction to achieve vibration in the axial direction and in the direction orthogonal to the axis L. In this case, the pneumatic vibration tool vibrates the grinding pin 10 at 5000 H / min or more.

[0029] In a case where a pneumatic vibrating tool is used, as in the Fig. 2, the grinding pin 10 can also be vibrated in the axial direction and in the direction orthogonal to the axis L when the distal end portion 17 of the grinding pin 10 is pressed obliquely against the surface S to be polished to polish the workpiece W.

[0030] As in the Fig. 5, the grinding pin 10 can be used with its proximal end portion attached to the head of a hand-held rotary tool 11'. In this case, as shown in the Fig. 4, the grinding pin attached to the rotary tool 11' is preferably a grinding pin 10' with a circular cross-section. In other words, it is preferable that the grinding pin 10' with a cylindrical shape is attached to the rotary tool 11'. The rotary tool 11' is, for example, an electric rotary tool or a pneumatic rotary tool. As indicated by the solid arrows in the Fig. 5, the rotary tool 11' rotates the grinding pin 10' around its axis.

[0031] As in the Fig. 5, when polishing the workpiece W, the grinding pin 10' is pressed obliquely at its distal end portion 17 against the surface S to be polished of the workpiece W. In other words, the grinding pin 10' is pressed against the surface S to be polished in a posture in which the angle θ between its axis L and the surface S to be polished is an acute angle. When polishing the workpiece W, the grinding pin 10' is pressed against the surface S to be polished of the workpiece W with a predetermined pressing force F from a direction along the axis L. In addition, the grinding pin 10' is rotated about the axis with the distal end portion 17 pressed against the surface S to be polished. The rotary tool 11' rotates the grinding pin 10 at 100 revolutions / min or more.

[0032] Even if the grinding pin 10' is attached to the rotary tool 11' for polishing, as shown in the Fig. 6, the distal end surface 17a of the grinding rod 10' can be pressed and rotated vertically against the surface S of the workpiece W to be polished. In this case, too, the grinding pin 10' is pressed against the surface S to be polished with a compressive force F from a direction along the axis L. The rotary tool 11' rotates the grinding pin 10 at 100 revolutions / min or more.

[0033] In any of the above polishing methods, when the grinding pin 10 is used to polish the surface S of the workpiece to be polished, it may bend in a direction intersecting its axis L due to the compressive force F pressing the grinding pin 10 against the surface S to be polished or the reaction force from the surface S to be polished.

[0034] The grinding pins 10 and 10' can also be used without being attached to a vibrating tool or the like. In this case, an operator presses the distal end portion 17 of the grinding pin 10, 10' against the surface S of the workpiece W to be polished to perform manual polishing. (Method for manufacturing the grinding pin)

[0035] The Fig. 7 is a flow chart of a method for manufacturing the grinding pin 10. As in the Fig. As shown in Fig. 7, a method for manufacturing the abrasive pin 10 includes a spinning step ST1, a pre-sintering step ST2, a sintering step ST3, and a resin impregnation and shaping step ST4 in this order. In the spinning step ST1, an aqueous spinning solution containing basic aluminum chloride, colloidal silicon oxide, and polyvinyl alcohol is dry-spun to obtain precursor fibers. In the pre-sintering step ST2, the precursor fibers are fired at 900 °C or higher and 1300 °C or lower to obtain inorganic filaments. In the sintering step ST3, the inorganic filaments are heated at high temperatures 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 pre-sintering step ST2.

[0036] In the resin impregnation and forming step ST4, the inorganic filaments are appropriately aligned to form yarn aggregates. In the resin impregnation and forming step ST4, the yarn aggregates are impregnated with a thermosetting resin such as epoxy resin or phenolic resin. Furthermore, in the resin impregnation and forming step ST4, the resin-impregnated yarn aggregates are aligned to form a bundle of yarn aggregates. Furthermore, in the resin impregnation and forming step ST4, the bundle of resin-impregnated yarn aggregates is drawn to pass through a nozzle having an opening of a predetermined shape and then cured in a heating furnace. The bundle of resin-cured yarn aggregates is then cut to a predetermined length. Thus, the grinding pin 10 with a predetermined length dimension and a predetermined cross-sectional shape is obtained.

[0037] A specific example of the manufacturing process is described below. First, in the spinning step ST1, 34 kg of an aqueous solution of basic aluminum chloride containing 13.2 wt.% aluminum ions and 11.45 wt.% chlorine ions, 7.5 kg of colloidal silica containing 20 wt.% silicon dioxide, and 2.5 kg of partially saponified polyvinyl alcohol with an average polymerization degree of 1700 are dissolved to prepare a spinning dope with a viscosity of approximately 1000 poise / 20°C. Next, the spinning dope is extruded through a 1000-hole spinneret for dry spinning. In the pre-sintering step ST2, the spun inorganic filaments are fired into ceramics at 900°C to 1300°C to obtain yarn aggregates. Subsequently, in the sintering step ST3, the yarn aggregates are passed through a tube furnace at 1300°C to 1400°C and continuously wound onto a first spool under tension.The throughput speed of the yarn units is adjusted so that the heating time is 20 seconds. The yarn units are wound onto a large number of initial bobbins.

[0038] In the resin impregnation and forming step ST4, the yarn aggregate is unwound from each of the first bobbins and passed through a resin tank containing uncured resin. The resin-impregnated yarn aggregates, passed through the resin tank, are aligned into a bundle, which is then passed through a heating furnace.

[0039] The resin for impregnating the yarn aggregates and the bundle of yarn aggregates may have the following composition.

[0040] Epoxy resin (jER828, manufactured by Mitsubishi Chemical Corporation) 100 parts by weight

[0041] Tetrahydromethylphthalic anhydride (HN-2200, manufactured by Hitachi Chemical Company, Ltd.) 85 parts by weight

[0042] Imidazole (2E4MZ-CN, manufactured by SHIKOKU KASEI HOLDINGS CORPORATION) 2 parts by weight

[0043] Here, in the resin impregnation and forming step ST4, the bundle of resin-impregnated yarn aggregates is passed through a die having an opening of a predetermined shape before reaching the heating furnace. As a result, the bundle of resin-impregnated yarn aggregates has a cross-sectional shape that matches the opening shape of the die. In the resin impregnation and forming step ST4, the impregnating resin is cured by means of the heating furnace. Thus, the bundle of resin-cured yarn aggregates is cut to a predetermined dimension. As a result, if the die has a rectangular opening, a grinding pin with a rectangular cross section and a predetermined length dimension can be obtained. If the die has a circular opening, a grinding pin with a circular cross section and a predetermined length dimension can be obtained. (Example 1)

[0044] The grinding pin 10 of Example 1 is rod-shaped and has a rectangular cross-section perpendicular to the axis. The grinding pin 10 has a thickness (shorter cross-sectional dimension) of 1 mm, a width (longer cross-sectional dimension) of 4 mm, and a length of 100 mm. The grinding pin 10 has a flexural strength of 1200 MPa and a flexural elasticity of 110 GPa.

[0045] The grinding pin 10 of Example 1 comprises the inorganic filaments 15 and the resin 16 impregnating the inorganic filaments 15. The inorganic filaments 15 contain 85 weight percent of an alumina component and 15 weight percent of a silica component. The crystal structure of the inorganic filaments 15 includes the alumina intermediate. The silica component is in an amorphous state. In other words, the crystal structure of the inorganic filaments 15 does not include mullite crystals. The inorganic filaments 15 have a BET specific area of ​​15 m 2 / g or less. In this example, the inorganic filaments 15 have a BET specific area of ​​12.5 m 2 / g. The cross sections of the inorganic filaments 15 are exposed on the distal end surface 17a of the grinding pin 10.

[0046] In the production of the grinding pin 10 of Example 1, the heating temperature in the pre-sintering step ST2 is 1000°C. The heating temperature in the sintering step ST3 is 1350°C. The heating time in the sintering step ST3 is 20 seconds.

[0047] The BET specific area is a specific area determined by a gas adsorption method (BET method). The BET specific area is measured after the sintering step ST3 and before the resin impregnation and molding step ST4.

[0048] Here, the absence of mullite crystals in the crystal structure of the inorganic filaments 15 was evaluated using X-ray diffraction. Specifically, in Example 1, a diffraction pattern was obtained by irradiating the inorganic filaments 15 with X-rays after the sintering step ST3 and before the resin impregnation and molding step ST4. Subsequently, it was confirmed that the peak of the diffraction line of the (210) plane of mullite did not appear near 26° of 2θ in the diffraction pattern. Fig. Figure 8 is a diffraction pattern obtained by irradiating the inorganic filaments 15 in Example 1 with X-rays. In the diffraction pattern in the Fig. 8 there is no peak near 26° of 2θ. (Example 2)

[0049] The grinding pin 10 of Example 2 is rod-shaped and has a rectangular cross-section perpendicular to the axis. The grinding pin 10 has a thickness dimension (shorter cross-sectional dimension) of 1 mm, a width dimension (longer cross-sectional dimension) of 4 mm, and a length dimension of 100 mm. The grinding pin 10 has a flexural strength of 1200 MPa and a flexural elasticity of 108 GPa.

[0050] The grinding pin 10 of Example 2 comprises the inorganic filaments 15 and the resin 16 impregnating the inorganic filaments 15. The inorganic filaments 15 contain 85 weight percent of an alumina component and 15 weight percent of a silica component. The crystal structure of the inorganic filaments 15 includes the alumina intermediate. The silica component is in an amorphous state. In other words, the crystal structure of the inorganic filaments 15 does not include mullite crystals. The inorganic filaments 15 have a BET specific area greater than 15 m 2 / g and 30 m 2 / g or less. In this example, the inorganic filaments 15 have a BET specific area of ​​28.7 m 2 / g. The cross sections of the inorganic filaments 15 are exposed on the distal end surface 17a of the grinding pin 10.

[0051] In the production of the grinding pin 10 of Example 2, the heating temperature in the pre-sintering step ST2 is 1000°C. The heating temperature in the sintering step ST3 is 1330°C. The heating time in the sintering step ST3 is 20 seconds.

[0052] Although not shown in the figure, the diffraction pattern obtained by irradiating the inorganic filaments 15 in Example 2 with X-rays does not have a peak near 26° of 2θ.

[0053] Here, the heating temperature in the sintering step ST3 in Example 1 is higher than the heating temperature in the sintering step ST3 in Example 2. As a result, the BET specific area of ​​the inorganic filaments 15 in the grinding pin 10 of Example 1 is less than half of the BET specific area of ​​the inorganic filaments 15 in the grinding pin 10 of Example 2. In other words, the BET specific area of ​​the inorganic filaments 15 can be controlled by controlling the heating temperature and the heating time in the sintering step ST3 in the production of the grinding pin 10.

[0054] The crystal structure of the inorganic filaments 15 in the grinding pin 10 of Example 1 is the state immediately before the appearance of mullite crystals in the crystal structure by sintering. (Comparison example 1)

[0055] A grinding pin of Comparative Example 1 is rod-shaped and has a rectangular cross-section perpendicular to the axis L. The grinding pin of Comparative Example 1 has a thickness dimension (shorter cross-sectional dimension) of 1 mm, a width dimension (longer cross-sectional dimension) of 4 mm, and a length dimension of 100 mm. The grinding pin of Comparative Example 1 has a flexural strength of 1100 MPa and a flexural elasticity of 105 GPa.

[0056] The grinding pin of Comparative Example 1 contains a plurality of inorganic filaments extending in the axial direction and a resin impregnating the inorganic filaments. The inorganic filaments contain 85 wt. % of an alumina component and 15 wt. % of a silica component. The crystal structure of the inorganic filaments includes the alumina intermediate. The silica component is in an amorphous state. In other words, the crystal structure of the inorganic filaments does not contain mullite crystals. The inorganic filaments have a BET specific area greater than 30 m². 2 / g. In this example, the inorganic filaments have a BET specific area of ​​51.0 m 2 / g. The cross sections of the inorganic filaments are exposed on the distal end face of the grinding pin of Comparative Example 1.

[0057] In the production of the grinding pin 10 of Comparative Example 1, the heating temperature in the pre-sintering step ST2 is 1000°C. The heating temperature in the sintering step ST3 is 1310°C. The heating time in the sintering step ST3 is 20 seconds.

[0058] The heating temperature in the sintering step ST3 in Comparative Example 1 is lower than the heating temperature in the sintering step ST3 in Examples 1 and 2. As a result, the BET specific surface area of the inorganic filaments in Comparative Example 1 is larger than the BET specific surface area of the inorganic filaments in Examples 1 and 2. The BET specific surface area of the inorganic filaments can be controlled by adjusting the heating temperature and the heating time in the sintering step ST3.

[0059] Although not shown in the figure here, the diffraction pattern obtained by irradiating the inorganic filaments in Comparative Example 1 with X-rays does not have a peak near 26° of 2θ. (Comparison example 2)

[0060] A grinding pin of Comparative Example 2 is rod-shaped and has a rectangular cross-section perpendicular to the axis L. The grinding pin of Comparative Example 2 has a thickness dimension (shorter cross-sectional dimension) of 1 mm, a width dimension (longer cross-sectional dimension) of 4 mm, and a length dimension of 100 mm. The grinding pin of Comparative Example 2 has a flexural strength of 1200 MPa and a flexural elasticity of 120 GPa.

[0061] The grinding pin of Comparative Example 2 contains a plurality of inorganic filaments extending in the axial direction and a resin impregnating the inorganic filaments. The inorganic filaments contain 85 wt. % of an alumina component and 15 wt. % of a silica component. The crystal structure of the inorganic filaments includes mullite crystals and an alumina intermediate. The crystal grains of the mullite crystals have an average grain size of 30 nm or larger. The inorganic filaments have a BET specific area of ​​0.5 m². 2 / g. The cross sections of the inorganic filaments are exposed on the distal end face of the grinding pin of Comparative Example 2.

[0062] In the production of grinding pin 2 of comparative example ST2, the heating temperature in the pre-sintering step is 1000°C. The heating temperature in the sintering step ST3 is 1390°C. The heating time in the sintering step ST3 is 30 seconds.

[0063] The heating temperature in the sintering step ST3 in Comparative Example 2 is higher than the heating temperature in the sintering step ST3 in Examples 1 and 2. The heating time in the sintering step ST3 in Comparative Example 2 is longer than the heating time in the sintering step ST3 in Examples 1 and 2. As a result, the grinding pin of Comparative Example 2 contains mullite crystals in the crystal structure. In other words, the presence or absence of mullite crystals in the crystal structure of the inorganic filaments can be controlled by controlling the heating temperature and heating time in the sintering step ST3 in the production of the grinding pin of Comparative Example 2.

[0064] Here, the presence of mullite crystals in the crystal structure of the inorganic filaments was evaluated using X-ray diffraction. In other words, in Comparative Example 2, a diffraction pattern was obtained by irradiating the inorganic filaments with X-rays after the sintering step ST3 and before the resin impregnation and molding step ST4. Subsequently, it was confirmed that the peak of the diffraction line of the (210) plane of mullite did not appear near 26° of 2θ in the diffraction pattern. Fig. Figure 9 is a diffraction pattern obtained by irradiating the inorganic filaments in Comparative Example 2 with X-rays. In the Fig. In the diffraction pattern shown in Figure 9, the peak appears near 26° of 2θ.

[0065] The average grain size of mullite crystals in the crystal structure of the inorganic filaments was calculated from the above diffraction pattern using the following general formula. Dhkl=0.9λβ12⋅cos θ D hkl : the average grain size of the (210) plane λ: the wavelength of the X-rays θ: the glancing angle of the X-rays β 1 / 2 : the full width at half height of the diffraction line of the (210) plane of mullite, in which the crystal structure 2θ appears by X-ray diffraction near 26°. (Comparison test)

[0066] A comparison test was conducted in which a workpiece W was polished using the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2. The Fig. Figure 10 is a roughness curve of a surface to be polished of a workpiece which was polished using the grinding pin 10 of Example 1. The Fig. 11 is a roughness curve of a surface to be polished of a workpiece which was polished using the grinding pin 10 of Example 2. The Fig. Figure 12 is a roughness curve of a workpiece surface to be polished, which was polished using the grinding pin of Comparative Example 1. The Fig. Figure 13 is a roughness curve of a workpiece surface to be polished using the grinding pin of Comparative Example 2. The Fig. 14 is a graph showing the amount of grinding of the workpiece W after the comparative test in which the workpiece W was polished with the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2. The Fig. 15 is a graph showing the amount of removal of each grinding pin after the comparison test in which the workpiece W was polished with the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2.

[0067] In the comparative test, the proximal end portion of each of the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2 was attached to the head of the hand-held vibration tool 11 to polish the surface S of the workpiece W to be polished. The vibration tool is a pneumatic vibration tool. The workpiece W to be polished is a mold. The workpiece W is made of S50C (carbon steel for machine construction).

[0068] More precisely, as in the Fig. 2, when polishing the workpiece W, the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2 were placed in a position where the angle θ between the axis L and the surface S to be polished was 30°. The distal end portions 17 of the grinding pins 10 of Examples 1 and 2 and the distal end portions of the grinding pins of Comparative Examples 1 and 2 were pressed against the surface S to be polished with a pressing force F of 6 N. Furthermore, the grinding pins 10 of Examples 1 and 2 and the grinding pins of Comparative Examples 1 and 2 were each vibrated in the axial direction by the vibration tool 11 at 21,000 H / min. Then, the workpiece W was continuously dry polished for 3 minutes on a polishing area of ​​30 mm × 30 mm.

[0069] As can be seen from the graph of the amount of grinding of the workpiece after the Fig. 14, the grinding pins 10 of Examples 1 and 2 have a grinding performance equivalent to that of the grinding pin of Comparative Example 2. In other words, even if the crystal structure of the inorganic filaments does not have mullite crystals, the grinding pin 10 with the inorganic filaments 15 having a BET specific area of ​​30 m 2 / g or less, can achieve grinding performance equivalent to that of a grinding pin in which the crystal structure of the inorganic filaments comprises mullite crystals and the alumina intermediate, and the crystal grains of the mullite crystals have an average grain size of 30 nm or larger.

[0070] As can be seen from the graph of the amount of grinding of the workpiece after the Fig. 14, the grinding performance of the grinding pin of Comparative Example 1 is inferior to the grinding pin of Comparative Example 2. In other words, the grinding pin of Comparative Example 1, in which the crystal structure of the inorganic filaments does not have mullite crystals and the inorganic filaments have a BET specific area greater than 30 m 2 / g, exhibit inferior grinding performance to the grinding pin of Comparative Example 2 in which the crystal structure of the inorganic filaments contains mullite crystals and the alumina intermediate, and the crystal grains of the mullite crystals have an average grain size of 30 nm or more.

[0071] The occurrence of scratches in the roughness curve of the surface S to be polished of the workpiece W, which was polished with the grinding pins 10 of Examples 1 and 2 shown in the Fig. 10 and the Fig. 11 is less frequent than the occurrence of scratches in the roughness curve of the surface S to be polished of the workpiece W which was polished with the grinding pin of Comparative Example 2 shown in the Fig. 13. In other words, when polishing is performed with the grinding pins 10 of Examples 1 and 2 in which the crystal structure of the inorganic filaments does not include mullite crystals, the occurrence of scratches can be suppressed compared with polishing with the grinding pin of Comparative Example 2 in which the crystal structure of the inorganic filaments includes mullite crystals.

[0072] Furthermore, the surface roughness of the surface to be polished S of the workpiece W polished with the grinding pin 10 of Example 1 is Rz 2.0 µm. The surface roughness of the surface to be polished S of the workpiece W polished with the grinding pin 10 of Example 2 is Rz 1.9 µm. The surface roughness of the surface to be polished S of the workpiece W after polishing with the grinding pin of Comparative Example 2 is Rz 4.1 µm. Thus, when polishing is performed using the grinding pins 10 of Examples 1 and 2 in which the crystal structure of the inorganic filaments does not include mullite crystals, the surface roughness of the surface to be polished S of the workpiece W can be improved compared to polishing using the grinding pin of Comparative Example 2 in which the crystal structure of the inorganic filaments includes mullite crystals.

[0073] In addition, the diagram shows the amount of material removed by the grinding pins after the Fig. 15, the comparative tests show that the amount of material removed by the grinding pins 10 of Examples 1 and 2 is less than the amount of material removed by the grinding pins of Comparative Examples 1 and 2. Thus, the grinding pin 10 in which the crystal structure of the inorganic filaments does not have mullite crystals and the inorganic filaments 15 has a BET specific area of ​​30 m 2 / g or less, have a higher abrasion resistance than the grinding pin of Comparative Example 1, in which the crystal structure of the inorganic filaments does not have mullite crystals and the inorganic filaments 15 have a BET specific area greater than 30 m 2 / g. The grinding pin 10, in which the crystal structure of the inorganic filaments does not contain mullite crystals and the inorganic filaments 15 have a BET specific area of ​​30 m 2 / g or less, has a higher abrasion resistance than the grinding pin of Comparative Example 2 in which the crystal structure of the inorganic filaments has mullite crystals.

[0074] According to the diagram of the amount of grinding of the workpiece W after the Fig. 14, the grinding pin 10 of Example 1, in which the inorganic filaments 15 have a BET specific area of ​​15 m 2 / g or less, have a higher grinding performance than the grinding pin 10 of Example 2 with a BET specific area of ​​over 15 m 2 / g. According to the diagram of the amount of removal of the grinding pins after the Fig. 15, the grinding pin 10 of Example 1, in which the inorganic filaments 15 have a BET specific area of ​​15 m 2 / g or less, having a higher abrasion resistance than the abrasive tip 10, where the abrasive tip 10 of Example 2 with a BET specific surface area of over 15 m 2 / g was used. (Operating effects)

[0075] In the abrasive tips 10 of Examples 1 and 2, the silicon dioxide component of the inorganic filaments 15 is in an amorphous state. Therefore, the crystal structure of the inorganic filaments 15 does not have mullite crystals. This structure can avoid the occurrence of scratches (polishing defects) on a surface to be polished of a workpiece due to mullite crystals. As a result, the surface roughness of the surface to be polished can be improved.

[0076] In the grinding pins 10 of Examples 1 and 2, the silicon dioxide component of the inorganic filaments 15 is in an amorphous state. In other words, the crystal structure of the inorganic filaments 15 does not contain mullite crystals. Therefore, the inorganic filaments 15 are not embrittled by the mullitization.

[0077] In addition, the inorganic filaments 15 in the grinding pins 10 of Examples 1 and 2 have a BET specific area of ​​30 m 2 / g or less. The inorganic filaments 15 with such a BET specific area have fewer pores and unevenness and therefore absorb less moisture. Thus, it is possible to prevent or suppress the inorganic filaments 15 from absorbing moisture from the air and preventing the curing of the resin impregnating the inorganic filaments 15.

[0078] Furthermore, since the inorganic filaments with such a BET specific area have fewer pores and unevenness, it is possible to avoid or suppress failure of the resin 16 in the grinding pin, which would otherwise be caused by bubbles remaining in the resin 16 impregnating the inorganic filaments. This can suppress the embrittlement of the grinding pin 10.

[0079] The Fig. 16 is a photograph of a side surface of the grinding pin 10 of Example 2. The Fig. 17 is a photograph of a side surface of the grinding pin of Comparative Example 1. As shown in Fig. As shown in Figure 17, the grinding pin of Comparative Example 1 with the inorganic filaments 15 having a large BET specific area exhibits an impregnation defect of the resin 16 due to bubbles remaining in the resin 16, and the surface of the grinding pin is rough (the rough areas appear in white in the photograph). In contrast, the surface of the grinding pin 10 of Example 2 with the inorganic filaments 15 having a BET specific area of ​​30 m 2 / g or less. In other words, no impregnation defect of the resin 16 in the grinding pin 10 of Example 2 with the inorganic filaments 15 having a BET specific area of ​​30 m 2 / g or less. When a side surface of the grinding pin 10 of Example 1 is photographed, a photograph similar to that shown in the Fig.16 can be obtained. Thus, no impregnation defect of the resin 16 is detected in the grinding pin 10 of Example 1.

[0080] Here, the inorganic filaments 15 in the grinding pins 10 of Examples 1 and 2 contain 80 weight percent or more of an aluminum oxide component. Thus, the hardness of the inorganic filaments 15 can be ensured. The inorganic filaments 15 with a BET specific surface area of ​​30 m 2 / g or less prevent the embrittlement of the grinding pins 10 of Examples 1 and 2, which would otherwise be caused by moisture absorption, which prevents the curing of the resin 16. In addition, the grinding pins 10 of Examples 1 and 2 are made with the inorganic filaments 15 having a BET specific surface area of ​​30 m 2 / g or less, the occurrence of resin impregnation failure is suppressed, and thus the embrittlement of the grinding pins 10 of Examples 1 and 2 is suppressed. Furthermore, unlike a rectangular grindstone which has the entire side surface in contact with the surface to be polished of the workpiece W during polishing, the grinding pin 10 performs polishing with the distal end portion 17 pressed against the surface to be polished of the workpiece W. Since the grinding pin 10 is elastic enough to bend in a direction intersecting its axis L, the distal end portion 17 of the grinding pin 10 can be pressed against the surface to be polished with a pressing force F, taking into account the elasticity of the grinding pin 10. Therefore, the grinding pins 10 of Examples 1 and 2 can ensure grinding performance even without mullite crystals in the crystal structure. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 10-183427

[0005]

Claims

[1] A rod-shaped grinding pin having a distal end portion which is pressed against a surface of a workpiece to be polished in order to polish the surface to be polished, the grinding pin comprising: a plurality of inorganic filaments extending in the axial direction; and a resin impregnated and cured in the inorganic filaments, wherein Cross sections of the inorganic filaments are exposed at a distal end surface of the grinding pin, the grinding pin is elastic to bend in a direction that intersects the axial direction, the inorganic filaments contain 80 to 90 percent by weight of an aluminum oxide component and 20 to 10 percent by weight of a silicon dioxide component, the inorganic filaments have a crystal structure containing the aluminum oxide intermediate, the silicon dioxide component is in an amorphous state, and the inorganic filaments have a BET specific area of ​​28.7 m 2 / g or less. [2] The grinding pin according to claim 1, wherein the inorganic filaments have a BET specific area of ​​12.5 m 2 / g or less. [3] The grinding pin according to claim 1, wherein the inorganic filaments comprise 85% by weight or more of an alumina component. [4] The grinding pin according to claim 1, wherein the resin is epoxy resin. [5] The grinding pin according to claim 1, wherein the grinding pin has a bending strength of 500 MPa or more and a bending elasticity of 50 GPa or more. [6] A polishing process comprising: attaching the grinding pin according to claim 1 to a vibrating tool; and vibrating a distal end portion of the grinding pin in the axial direction while the distal end portion is pressed against a surface of a workpiece to be polished. [7] A polishing process comprising: attaching the grinding pin according to claim 1 to a vibrating tool; and vibrating a distal end portion of the grinding pin in an axial direction and in a direction intersecting an axis of the grinding pin while pressing the distal end portion against a surface of a workpiece to be polished. [8] A polishing process comprising: attaching the grinding pin according to claim 1 to a rotary tool; and rotating a distal end portion of the grinding pin which is pressed against a surface of a workpiece to be polished, wherein the grinding pin has a circular cross-section.

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