JP2018203562A - Method for producing glass rolling element - Google Patents

Abstract

To create a method that makes it possible to prepare a glass rolling element having high mechanical strength and dimension accuracy.SOLUTION: A method for producing a glass rolling element has a first polishing step for polishing the glass surface of spherical glass, an ion exchange treatment step for subjecting the spherical glass to ion exchange treatment after the first polishing step, to obtain a glass rolling element having a surface compressive stress layer, and a second polishing step for polishing the glass surface of the glass rolling element after the ion exchange treatment step.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a glass rolling element, and more particularly to a method for manufacturing a glass rolling element having high mechanical strength and high dimensional accuracy.

  Silicon nitride is widely used for rolling elements that require insulation. A rolling element made of silicon nitride has the advantage of high insulation and high strength. On the other hand, a rolling element made of silicon nitride has a demerit that it has a high density and is difficult to process into a spherical shape (see Patent Document 1).

  On the other hand, glass is an insulating material and has good moldability and workability. However, since glass is a brittle material, when it is used for a rolling element incorporated in a bearing device or the like, it may be damaged under severe conditions such as high-speed rotation, high friction, and high load. Therefore, when the glass is subjected to ion exchange treatment, a surface compressive stress layer is formed, and the mechanical strength can be increased (see Patent Document 2).

JP 2009-190959 A JP 2017-15147 A

  However, when a rolling element is produced by ion exchange treatment of glass, there is a problem that it is difficult to obtain high dimensional accuracy.

  This invention is made | formed in view of the said situation, and is creating a method which can produce a glass rolling element with high mechanical strength and dimensional accuracy.

  As a result of various studies, the present inventor has obtained the following knowledge. Chemically strengthened glass subjected to ion exchange treatment generally has a higher mechanical strength as the stress depth DOL of the surface compressive stress layer is larger. On the other hand, a large amount of alkali ions having a large ion radius is present on the glass surface. The glass surface expands. This dimensional change is not a big problem in the case of chemically tempered glass used in applications such as cover glass, but is a level that cannot be ignored in the application of rolling elements. When spherical glass is ion-exchanged to obtain a glass rolling element, when the glass surface of the spherical glass expands, the dimensional tolerance of the diameter of the glass rolling element increases. As a result, when the glass rolling element is incorporated into a bearing device or the like, the glass surface is worn heavily by sliding with the bearing, or the probability of breakage is increased. And this inventor discovers that the said technical subject can be solved by providing a grinding | polishing process before and after the ion exchange process of spherical glass, respectively, and proposes as this invention. That is, the method for producing a glass rolling element of the present invention includes a first polishing step for polishing a glass surface of a spherical glass, and a glass having a surface compressive stress layer by ion-exchange treatment of the spherical glass after the first polishing step. An ion exchange treatment step for obtaining a rolling element, and a second polishing step for polishing the glass surface of the glass rolling element after the ion exchange treatment step are provided.

  According to the inventor's investigation, when a spherical glass is subjected to ion exchange treatment to form a surface compressive stress layer, ions having a large ion radius (for example, K ions) enter the glass surface, and the glass surface expands. Due to this surface expansion, the dimensional accuracy of the glass rolling element is likely to decrease. Furthermore, when ion exchange treatment is performed, there is a difference in the degree of ion exchange even within a single glass sphere, and in particular, ion exchange in the region in contact with the ion exchange jig is hindered. Accuracy is likely to decrease. Then, the manufacturing method of the glass rolling element of this invention provides a grinding | polishing process (1st grinding | polishing process) before an ion exchange treatment process, and also provides a grinding | polishing process (2nd grinding | polishing process) after an ion exchange treatment process. Yes. This makes it possible to produce a glass rolling element with high mechanical strength and dimensional accuracy.

  Secondly, in the method for producing a glass rolling element of the present invention, it is preferable to polish the glass surface of the spherical glass so that the dimensional tolerance of the diameter is within 0.01%. Here, the “diameter dimensional tolerance” is a dimensional tolerance with respect to the average value of the diameters measured at at least 10 locations, and can be measured by, for example, a well-known contact type length measuring machine.

  Thirdly, it is preferable that the manufacturing method of the glass rolling element of this invention grind | polishes the glass surface of a glass rolling element so that the dimensional tolerance of a diameter may be less than 0.01%.

  Fourthly, in the method for producing a glass rolling element of the present invention, it is preferable to polish the glass surface of the spherical glass so that the dimensional tolerance between lots is within 1 μm. According to the inventor's investigation, depending on the temperature distribution in the ion exchange tank, there is a difference in the degree of ion exchange even in production in the same lot, but when a polishing step is provided before and after the ion exchange treatment of the spherical glass, The difference can be reduced to within 1 μm. Here, the “dimensional tolerance between lots” is the difference between the average diameter of the largest sphere in the lot and the average diameter of the smallest sphere, as described in JIS B1563 “Rolling bearings—silicon nitride spheres”. .

  Fifth, in the method for producing a glass rolling element of the present invention, it is preferable to polish the glass surface of the glass rolling element so that the difference between lots is within 1 μm.

  Sixth, it is preferable that the glass rolling element manufacturing method of this invention grind | polishes the glass surface of a glass rolling element so that it may become 2-50% of polishing width of the stress depth DOL of a surface compressive-stress layer.

  Seventh, in the method for producing a glass rolling element of the present invention, it is preferable to polish the glass surface of the glass rolling element so that the surface roughness Ra of the surface becomes 5 nm or less. If it does in this way, it will become difficult to break a glass rolling element on severe conditions, such as high-speed rotation, high friction, and high load. Here, the “surface roughness Ra” can be measured by a method based on JIS B0601: 2001 in a state where the sample is fixed with a jig or the like.

  Eighth, in the method for producing a glass rolling element of the present invention, it is preferable to polish the glass surface of the glass rolling element so that the compressive stress value CS of the surface compressive stress layer is 100 MPa or more.

Ninth, method of manufacturing a glass rolling elements of the present invention, glass rolling elements, as a glass composition, in _{mass%, SiO 2 45~75%, Al} 2 O 3 10~30%, Na 2 O 5~25 % Glass is preferable.

Tenth, in the method for producing a glass rolling element according to the present invention, the glass rolling element is preferably made of glass having a liquidus viscosity of 10 ^4.0 dPa · s or more.

Eleventhly, in the method for producing a glass rolling element of the present invention, the ion exchange treatment is preferably performed by immersing the spherical glass in KNO ₃ molten salt.

  12thly, the manufacturing method of the glass rolling element of this invention performs an ion exchange process so that the compressive stress value CS of the surface compressive stress layer of a glass rolling element may be 300 Mpa or more, and the stress depth DOL may be 30 micrometers or more. It is preferable. Here, the “compressive stress value CS” and the “stress depth DOL” are measured as follows. A glass plate having the same composition as the spherical glass and the same thermal history is prepared. Next, the glass plate is subjected to ion exchange treatment under the same conditions as the spherical glass to obtain a glass plate having the same surface composition profile as the spherical glass. The surface composition profile can be measured by using a standardless quantitative analysis of the ZAF method by SEM-EDX (for example, S4300-SE manufactured by Hitachi High-Technologies, EX-250 manufactured by Horiba, Ltd.). In addition, about the glass which is the same composition, a heat history can be arrange | equalized by making the density measured by the well-known Archimedes method or the heavy liquid method the same. Subsequently, the cross section of the glass plate is observed with a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho Co., Ltd.), and the compression stress value CSp of the surface stress layer of the glass plate is determined from the number of observed interference fringes and the interval between them. The stress depth DOLp is calculated. Finally, the obtained CSp is evaluated as CS of spherical glass, and DOLp is evaluated as DOL of spherical glass. The “compressive stress value CS” can also be directly measured by the retardation of the surface compressive stress layer using the birefringence imaging system Abrio.

  As described above, the method for producing a glass rolling element of the present invention comprises a first polishing step for polishing the glass surface of the spherical glass, and after the first polishing step, the spherical glass is subjected to an ion exchange treatment to form a surface compressive stress layer. An ion exchange treatment step for obtaining a glass rolling element, and a second polishing step for polishing the glass surface of the glass rolling member after the ion exchange treatment step are provided. Hereinafter, about the manufacturing method of the glass rolling element of this invention, a detail is demonstrated along each process.

  The spherical glass used for the manufacturing method of the glass rolling element of this invention can be produced as follows, for example. First, a glass batch prepared to have a desired glass composition is put into a continuous melting furnace, heated and melted at 1500 to 1600 ° C. to obtain a molten glass, and then a molding apparatus through a clarification container and a stirring container. And then, it is formed into a spherical shape and slowly cooled.

  Various molding methods can be adopted as the molding method. In particular, it is preferable to adopt a marble molding method or a droplet molding method. If it does in this way, it will become easy to shape spherical glass with high dimensional accuracy. As a result, the dimensional tolerance of the diameter can be reduced with a small amount of polishing of the glass surface.

The spherical glass (glass rolling element) according to the present invention preferably contains, as a glass composition, mass%, SiO ₂ 45 to 75%, Al ₂ O ₃ 10 to 30%, and Na ₂ O 5 to 25%. . The reason for limiting the content range of each component as described above will be described below. In addition, in description of the content range of each component, the following% display points out the mass% unless there is particular notice.

SiO ₂ is a component that forms a glass network, and the content thereof is preferably 45 to 75%, 45 to 70%, 45 to 65%, 45 to 63%, particularly 48 to 61%. When the content of SiO ₂ is too large, meltability, moldability, thermal expansion coefficient is liable to lower. On the other hand, if the content of SiO ₂ is too small, it becomes difficult to vitrify and the thermal expansion coefficient becomes unreasonably high, so that the thermal shock resistance tends to decrease.

Al ₂ O ₃ is a component that increases ion exchange performance, strain point, and Young's modulus. However, when the content of Al ₂ O ₃ is too large, devitrification crystal glass becomes easy to precipitate, hardly molded into a desired shape. Further, the meltability and the coefficient of thermal expansion are likely to decrease. Therefore, the preferred upper limit range of Al ₂ O ₃ is 30% or less, 28% or less, 24% or less, 23% or less, 22% or less, 21.5% or less, particularly 21% or less. 10% or more, 12% or more, 13% or more, 15% or more, 17% or more, particularly 18% or more.

Na ₂ O is an ion exchange component and a component that improves meltability and moldability. It is also a component that improves devitrification resistance. However, when the content of Na ₂ O is too large, the volume electrical resistivity is lowered or the thermal expansion coefficient is unduly increased, so that the thermal shock resistance tends to be lowered. Further, the balance of the glass composition may be lost, and the devitrification resistance may be reduced. Therefore, the content of Na ₂ O is preferably 5 to 25%, 10 to 25%, 11 to 22%, 12 to 20%, 13 to 19%, particularly 14 to 18%.

  In addition to the above components, for example, the following components may be introduced.

P ₂ O ₅ is a component that enhances the ion exchange performance, and particularly a component that increases the stress depth DOL. As described above, increasing the amount of Al ₂ O ₃ is effective for improving the ion exchange performance. However, if the content of Al ₂ O ₃ is too large, the devitrification resistance tends to decrease. Therefore, there is a limit to the amount of Al ₂ O ₃ introduced. However, when P ₂ O ₅ is introduced, even if the amount of Al ₂ O ₃ is increased, it becomes difficult for the glass to devitrify, so that the allowable amount of introduction of Al ₂ O ₃ can be increased. As a result, ion exchange performance can be dramatically improved. On the other hand, if too much amount of P ₂ O _5, glass or phase separation, the water resistance and the devitrification resistance tends to decrease. In view of the above points, the preferable upper limit range of P ₂ O ₅ is 10% or less, 9% or less, 8% or less, 7% or less, particularly 6% or less, and the preferable lower limit range is 0% or more, 0 1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, particularly 4% or more.

B ₂ O ₃ is a component that lowers the liquidus temperature, the high-temperature viscosity, and the density, and is a component that increases the ion exchange performance, particularly the compressive stress value CS. There is a possibility that burns may occur on the surface, and water resistance, liquid phase viscosity, and stress depth DOL may decrease. Therefore, the content of B ₂ O ₃ is preferably 0 to 6%, 0 to 4%, 0.1 to 3%, 0.1 to 2%, particularly 0.5 to less than 1%.

Li ₂ O is an ion exchange component and a component that lowers the high-temperature viscosity and improves the meltability and moldability. Furthermore, it is a component that increases the Young's modulus. However, when the content of Li 2 _O is too large, and decreases the liquidus viscosity, it tends glass devitrified. Further, the low-temperature viscosity is excessively lowered, and stress relaxation is likely to occur during the ion exchange treatment, and the compressive stress value CS may be lowered. Therefore, the content of Li ₂ O is preferably 0 to 10%, 0 to 8%, 0 to 5%, 0 to less than 3%, 0 to 2%, 0 to less than 1%, 0 to 0.1%. Less than, especially 0 to less than 0.01%.

K ₂ O is a component that promotes ion exchange, and is a component that has a high effect of increasing the stress depth DOL, particularly among alkali metal oxides. Further, it is a component that lowers the high-temperature viscosity to increase meltability and moldability, and improve devitrification resistance. However, if the content of K ₂ O is too large, the thermal expansion coefficient becomes unreasonably high, the thermal shock resistance is lowered, and it is difficult to match the thermal expansion coefficient with the surrounding materials. Furthermore, there is a possibility that the strain point is excessively lowered, the balance of the glass composition is lost, and the devitrification resistance is reduced. The preferable upper limit range of K ₂ O is 10% or less, 9% or less, 8% or less, 7% or less, particularly 6% or less, and the preferable lower limit range is 0% or more, 0.5% or more, 1% or more. 2% or more, 3% or more, particularly 4% or more.

The preferred upper limit range of Li ₂ O + Na ₂ O + K ₂ O is 30% or less, 25% or less, particularly 22% or less, and the preferred lower limit range is 8% or more, 10% or more, 13% or more, particularly 15% or more. is there. If the content of Li ₂ O + Na ₂ O + K ₂ O is too large, the devitrification resistance is lowered, the thermal expansion coefficient is unduly high, the thermal shock resistance is lowered, and the thermal expansion coefficient matches with the surrounding materials. It becomes difficult to do. On the other _hand, if too small content of _{Li 2 O + Na 2 O +} K 2 O, becomes liable to lower the melting property and ion-exchange performance. “Li ₂ O + Na ₂ O + K ₂ O” is the total amount of Li ₂ O, Na ₂ O and K ₂ O.

The molar ratio K ₂ O / Na ₂ O is preferably 0 to 1, 0 to 0.8, 0.05 to 0.7, 0.1 to 0.5, 0.15 to 0.4, 0. 15-0.3, especially 0.15-0.25. In this way, the compressive stress value CS and the stress depth DOL are likely to increase in a short time. Also, a relatively high electrical resistivity can be obtained by the well-known mixed alkali effect. “K ₂ O / Na ₂ O” is a value obtained by dividing the content of K ₂ O by the content of Na ₂ O.

  The content of MgO + CaO + SrO + BaO is preferably 0-15%, 0-9%, 0.5-6%, especially 1-5%. When there is too much content of MgO + CaO + SrO + BaO, a density and a thermal expansion coefficient will become unreasonably high, or devitrification resistance and ion exchange performance will fall easily. “MgO + CaO + SrO + BaO” is the total amount of MgO, CaO, SrO and BaO.

  MgO and CaO are components that lower high-temperature viscosity to increase meltability and moldability, and increase strain point and Young's modulus. Among alkaline earth metal oxides, MgO and CaO are highly effective in increasing ion exchange performance. It is an ingredient. However, when the contents of MgO and CaO increase, the density and thermal expansion coefficient increase and the glass tends to devitrify. Therefore, the content of MgO is preferably 10% or less, 8% or less, 6% or less, 0.5 to 5%, particularly 1 to 4%. The content of CaO is preferably 6% or less, 4% or less, 2% or less, less than 1%, particularly less than 0.5%.

  SrO and BaO are components that lower the high temperature viscosity to increase the meltability and formability, and increase the strain point and Young's modulus. However, when the contents of SrO and BaO increase, the density and thermal expansion coefficient increase, and the ion exchange performance tends to decrease. Therefore, the content of SrO is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly less than 0.1%. The content of BaO is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, particularly less than 0.1%.

The mass ratio (MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.5 or less, 0.4 or less, particularly 0.3 or less, in order to increase the devitrification resistance. “(MgO + CaO + SrO + BaO) / (Li ₂ O + Na ₂ O + K ₂ O)” is a value obtained by dividing the total amount of MgO, CaO, SrO and BaO by the total amount of Li ₂ O, Na ₂ O and K ₂ O. .

ZnO is a component that enhances ion exchange performance. Moreover, it is a component which reduces high temperature viscosity, without reducing low temperature viscosity. However, when ZnO is increased in the presence of P ₂ O ₅ , the glass is likely to undergo phase separation or devitrification. Therefore, the ZnO content is preferably 8% or less, 4% or less, 1% or less, 0.1% or less, and particularly 0.01% or less.

ZrO ₂ is a component that increases ion exchange performance, Young's modulus, and strain point, and is a component that decreases high temperature viscosity. However, when the content of ZrO ₂ increases, the devitrification resistance tends to be lowered. Therefore, the content of ZrO ₂ is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to less than 1%, 0 to 0.4%, especially 0 to less than 0.1%.

TiO ₂ is a component that enhances ion exchange performance and is a component that reduces high temperature viscosity. However, when the content of TiO ₂ increases, the glass is likely to be colored or devitrified. In particular, the transmittance tends to fluctuate due to the melting atmosphere and the raw material impurities. Therefore, the content of TiO ₂ is preferably 0 to 4%, 0 to less than 1%, 0 to less than 0.1%, particularly 0 to less than 0.01%.

SnO ₂ is a component that increases the ion exchange performance, particularly the compressive stress value CS. However, when the content of SnO ₂ increases, devitrification due to SnO ₂ occurs or glass tends to be colored. Therefore, the content of SnO ₂ is preferably 0 to 3%, 0.01 to 2%, 0.05 to 1%, particularly 0.1 to 0.5%.

As a fining _{agent, As 2 O 3, Sb 2} O 3, CeO 2, F, may contain _SO 3, Cl one or two or more selected from the group of. However, from environmental considerations, it is preferred that no added _As 2 _{O 3} and _Sb 2 _{O 3,} the content of _As 2 _{O 3} and _Sb 2 _{O 3} content _of each less than 0.1%, particularly less than 0.01% Is preferred. The CeO ₂ content is preferably less than 0.1%, particularly preferably less than 0.01%, in order to increase the transmittance. The content of F is less than 0.1%, particularly less than 0.01%, in order to suppress stress relaxation due to a decrease in low-temperature viscosity.

  Transition metal oxides such as CoO and NiO are components that color glass. Therefore, the content of the transition metal oxide is preferably 0.5% or less, 0.1% or less, particularly 0.05% or less.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus. However, when the content of the rare earth oxide increases, the raw material cost increases, and the devitrification resistance tends to decrease. Therefore, the rare earth oxide content is preferably 3% or less, 2% or less, less than 1%, 0.5% or less, particularly 0.1% or less.

The contents of PbO and Bi ₂ O ₃ are each preferably less than 0.1% in consideration of the environment.

  The spherical glass (glass rolling element) of the present invention preferably has the following glass characteristics.

Density is preferably 2.60 g / cm ³ or less, 2.55 g / cm ³ or less, 2.50 g / cm ³ or less, 2.49 g / cm ³ or less, in particular 2.48 g / cm ³ or less. As the density is lower, the glass rolling element can be reduced in weight. “Density” refers to a value measured by the well-known Archimedes method.

The thermal expansion coefficient in the temperature range of 30 to 380 ° C. is preferably 70 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C., 75 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C., 80 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C., in particular 85 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C. If the coefficient of thermal expansion is regulated as described above, even if the surrounding metal member expands due to heat generated during high-speed rotation, it can be driven properly. Here, the “thermal expansion coefficient” is an average value measured with a dilatometer in a temperature range of 30 to 380 ° C.

  The strain point is preferably 520 ° C. or higher, 550 ° C. or higher, 560 ° C. or higher, particularly 570 to 750 ° C. The higher the strain point, the better the heat resistance. In addition, when the strain point is high, stress relaxation is less likely to occur during the ion exchange process, and thus it is easy to ensure a high compressive stress value CS.

The temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or lower, 1600 ° C. or lower, 1580 ° C. or lower, 1550 ° C. or lower, 1540 ° C. or lower, especially 1530 ° C. or lower. The lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s, the more the glass can be melted at a lower temperature. Therefore, as the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is lower, the burden on glass production equipment such as a melting kiln is reduced, and the bubble quality of the spherical glass can be improved.

  The liquidus temperature is preferably 1200 ° C. or lower, 1150 ° C. or lower, 1130 ° C. or lower, 1110 ° C. or lower, 1090 ° C. or lower, particularly 1070 ° C. or lower. When the liquidus temperature is too high, it becomes difficult to form a spherical shape.

Liquidus viscosity, preferably of ¹⁰ 4.0 dPa · s or ^{more, 10} 4.3 dPa · s or ^{more, 10} 4.5 dPa · s or ^{more, 10} 5.0 dPa · s or more, particularly ¹⁰ 5.4 dPa · s or more. When the liquidus viscosity is too low, it becomes difficult to form a spherical shape. If the liquid phase temperature is 1200 ° C. or lower and the liquid phase viscosity is 10 ^4.0 dPa · s or higher, it can be formed into a spherical shape by a marble molding method or the like.

  The manufacturing method of the glass rolling element of this invention is equipped with the 1st grinding | polishing process of grind | polishing the glass surface of spherical glass. Various methods can be adopted as a method of polishing the glass surface of the spherical glass, but a method of polishing while rotating the spherical glass is preferable in reducing the dimensional tolerance of the diameter.

  In the first polishing step, the dimensional tolerance of the diameter is within 0.01%, within 0.005%, within 0.003%, within 0.002%, within 0.0015%, especially within 0.001%. Thus, it is preferable to polish the glass surface of the spherical glass. If the dimensional tolerance of the diameter of the spherical glass is too large, the dimensional tolerance of the diameter of the glass rolling element becomes too large due to the ion exchange treatment, and then the polishing width is changed to the stress depth of the surface compressive stress layer in the second polishing step. If it is not more than DOL, it will be difficult to increase the dimensional accuracy of the glass rolling element. As a result, it becomes difficult to achieve both the mechanical strength and dimensional accuracy of the glass rolling element.

  In the first polishing step, it is preferable to polish the glass surface of the spherical glass so that the diameter is 100 mm or less, 80 mm or less, 50 mm or less, 30 mm or less, 20 mm or less, particularly 10 mm or less, 1 mm or more, 2 mm or more, The glass surface of the spherical glass is preferably polished so as to be 4 mm or more, particularly 5 mm or more. If it does in this way, it will become suitable for a rolling element built in a bearing device etc.

  The manufacturing method of the glass rolling element of this invention has an ion exchange treatment process of obtaining the glass rolling element which ion-exchange-processes spherical glass and has a surface compressive-stress layer after a 1st grinding | polishing process.

  The ion exchange treatment is preferably performed so that the compressive stress value CS of the surface compressive stress layer of the glass rolling element is 100 MPa or more, 300 MPa or more, 500 MPa or more, particularly 700 MPa or more. The larger the compressive stress value CS, the higher the mechanical strength of the glass rolling element. However, if the compressive stress value CS is too large, the tensile stress value CT inherent in the glass rolling element may be extremely high. Therefore, the compressive stress value CS of the surface compressive stress layer is preferably 2500 MPa or less. Note that the compression stress value CS can be increased by shortening the ion exchange time or lowering the ion exchange temperature (the temperature of the ion exchange solution).

  The ion exchange treatment is preferably performed so that the stress depth DOL of the surface compressive stress layer of the glass rolling element is 10 μm or more, 30 μm or more, 50 μm or more, particularly 70 μm or more. The greater the stress depth DOL, the more difficult the glass rolling element breaks even if the glass surface of the glass rolling element is deeply damaged due to wear or foreign matter during high rotation. On the other hand, if the stress depth DOL is too large, the tensile stress value CT inherent in the glass rolling element may be extremely high. Therefore, the stress depth DOL is preferably 500 μm or less, 300 μm or less, and particularly 200 μm or less. Note that the stress depth DOL can be increased by increasing the ion exchange time or raising the ion exchange temperature.

  The ion exchange treatment is preferably performed so that the tensile stress value CT inside the glass rolling element is 200 MPa or less, 150 MPa or less, 100 MPa or less, and particularly 50 MPa or less. The smaller the internal tensile stress value CT, the harder the glass rolling element is damaged by internal defects. However, when the internal tensile stress value CT becomes extremely small, the compressive stress value CS and the stress depth DOL decrease, The mechanical strength of a glass rolling element will fall. Therefore, the ion exchange treatment is preferably performed so that the tensile stress value CT inside the glass rolling element is 1 MPa or more, 10 MPa or more, particularly 15 MPa or more. The “internal tensile stress value CT” refers to a value calculated by the following mathematical formula 1. Here, t: the thickness of the glass rolling element refers to the shortest distance among the distances between the opposing surfaces of the rolling element.

[Equation 1]
CT = CS × DOL / (t × 1000-2 × DOL)
CT: Internal tensile stress value (MPa)
t: Diameter of glass rolling element (mm)
CS: Compressive stress value (MPa)
DOL: Stress depth (μm)

The ion exchange treatment can be performed by immersing the spherical glass in KNO ₃ molten salt at 360 to 500 ° C. (preferably 370 to 430 ° C.) for ₄ to 120 hours (preferably 24 to 100 hours). From the viewpoint of production efficiency of the glass rolling element, it is preferable to simultaneously ion exchange a plurality of spherical glasses. In this case, a metal jig having a mesh width smaller than the diameter of the spherical glass so that the spherical glasses do not contact each other. More preferably, a plurality of spherical glasses are arranged at equal intervals and the ion exchange treatment is performed in a state where the jig is laminated.

The method of manufacturing a glass rolling elements of the present invention, as content of K _{2 O} of the glass surface of the glass rolling element is greater than the content of the interior of K _{2 O,} it is preferred to ion-exchange treatment. If it does in this way, the mechanical strength of a glass rolling element can be raised. Difference in content between the interior of _{K 2} O of _{K 2} O of the glass surface is preferably 1 mol% or more, 3 mol% or more, 5 mol% or more, 7 mol% or more, 8 mol% or more, 9 It is at least 10 mol%, particularly at least 10 mol%. Here, the content of K ₂ O on the glass surface and inside is measured by using standardless quantitative analysis by the ZAF method by SEM-EDX (for example, S4300-SE manufactured by Hitachi High-Technologies, EX-250 manufactured by Horiba, Ltd.). be able to. “Content of K ₂ O on the glass surface” refers to a value obtained by analyzing a depth of 2.5 μm from the glass surface by the method described above. The “internal K ₂ O content” refers to a value obtained by analyzing a region where ions are not exchanged by the above-described method. In addition, when high purity KNO ₃ molten salt is used as the ion exchange solution or the content of Na ₂ O in the glass composition of the spherical glass is increased, the K ₂ O content on the glass surface of the glass rolling element is increased. It tends to be larger than the content of K ₂ O.

  In the method for producing a glass rolling element of the present invention, ion exchange is performed so that the volume resistivity ratio R at 150 ° C. before and after ion exchange treatment is 10 or more, 50 or more, 100 or more, 200 or more, particularly 300 or more. It is preferable to carry out the treatment. The larger the value of R, the easier it is to improve the insulating properties of the glass rolling element by the ion exchange treatment.

The volume resistivity ρ at 150 ° C. of the glass rolling element is preferably 10 ^5.0 Ω · cm or more, 10 ^5.5 Ω · cm or more, 10 ^6.0 Ω · cm or more, 10 ^6.5 Ω · cm. ^Or more, 10 ^7.0 Ω · cm or more, 10 ^7.5 Ω · cm or more, 10 ^8.0 Ω · cm or more, 10 ^8.5 Ω · cm or more, 10 ^8.7 Ω · cm or more, 10 ^{9. It is 0} Ω · cm or more, particularly 10 ^9.5 Ω · cm or more. When the volume electrical resistivity is low, the insulating property of the glass rolling element tends to be lowered.

  The ion exchange treatment may be performed a plurality of times. When the ion exchange treatment is performed a plurality of times, the distribution curve of the K ion concentration in the depth direction can be bent, and the compressive stress value CS and the stress depth DOL of the surface compressive stress layer are increased and accumulated inside. The total amount of tensile stress can be reduced.

  When the ion exchange treatment is performed twice, a heat treatment step may be provided between the ion exchange treatments. In this way, the K ion concentration distribution curve in the depth direction can be bent by the same potassium nitrate molten salt. Furthermore, the time for the first ion exchange treatment can be shortened.

  The manufacturing method of the glass rolling element of this invention has a 2nd grinding | polishing process which grind | polishes the glass surface of a glass rolling element. Various methods can be adopted as a method of polishing the glass surface of the glass rolling element, but a method of polishing while rotating the glass rolling element is preferable in reducing the dimensional tolerance of the diameter.

  In the second polishing step, the glass surface of the glass rolling element is polished so that the dimensional tolerance of the diameter is within 0.01%, within 0.005%, within 0.003%, and particularly within 0.001%. It is preferable. If the dimensional tolerance of the diameter of the glass rolling element is too large, the driving operation or the like becomes unstable, making it difficult to use as a rolling element.

  The glass surface of the glass rolling element is preferably polished so that the polishing width is 2 to 50%, 5 to 40%, particularly 8 to 25% of the stress depth DOL of the surface compressive stress layer. If the polishing width is too small, the dimensional accuracy of the glass rolling element is liable to be lowered, so that the driving operation or the like becomes unstable, making it difficult to use as the rolling element. On the other hand, if the polishing width is too large, the mechanical strength of the glass rolling element decreases.

  In the second polishing step, it is preferable to polish the glass surface of the glass rolling element so that the surface roughness Ra of the glass surface is 5 nm or less, 4 nm or less, particularly 3 nm or less. If the surface roughness Ra of the glass surface is too large, the glass rolling element tends to be damaged under severe conditions such as high-speed rotation, high friction, and high load.

  The glass surface of the glass rolling element is preferably polished so that the compressive stress value CS of the surface compressive stress layer is 100 MPa or more, 200 MPa or more, and particularly 500 MPa or more. If the compressive stress value CS of the surface compressive stress layer is too small, the mechanical strength of the glass rolling element is reduced, so that the glass rolling element is likely to be damaged under severe conditions such as high-speed rotation, high friction, and high load. .

  After the second polishing step, a cleaning step for removing polishing powder may be provided, or a chemical etching step for removing polishing scratches may be provided.

  The present invention will be described based on examples. However, the present invention is not limited to the following examples. The following examples are merely illustrative.

  Table 1 shows the glass composition and glass properties of the spherical glass.

  Each sample described in Table 1 was produced as follows. First, the glass raw material was prepared so that it might become the glass composition in a table | surface, and it melted at 1580 degreeC for 8 hours using the platinum container. Thereafter, the molten glass was poured out on the carbon plate and formed into a plate shape to obtain a glass plate. Separately, a molten glass having the glass composition of Sample A was formed into a dice shape to obtain a dice glass, and then reshaped into a spherical glass as described later. Note that the glass plate and spherical glass having the glass composition of sample A have the same thermal history, and when ion exchange treatment is performed under the same ion exchange conditions, both the surface composition profile and the state of the surface compressive stress layer are also present. Be the same.

  Next, various characteristics of the glass used for the spherical glass were evaluated.

  The density ρ is a value measured by the well-known Archimedes method.

  The thermal expansion coefficient α is an average value measured with a dilatometer in a temperature range of 30 to 380 ° C.

  The Young's modulus E is a value measured by a known resonance method.

  The strain point Ps and the annealing point Ta are values measured by the method of ASTM C336.

  The softening point Ts is a value measured by the method of ASTM C338.

The temperature corresponding to the high temperature viscosity of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s, 10 ^2.5 dPa · s is a value measured by the platinum ball pulling method.

  The liquid phase temperature TL passes through a standard sieve 30 mesh (a sieve opening of 500 μm), and the glass powder remaining in a 50 mesh (a sieve opening of 300 μm) is put in a platinum boat and kept in a temperature gradient furnace for 24 hours to obtain a crystal. It is the value which measured the temperature which deposits.

  The volume resistivity ρb before the ion exchange treatment is a value measured at 150 ° C. based on ASTM C657-78 using a 0.7 mm thick plate-like sample as a measurement sample.

Subsequently, after performing optical polishing on both glass surfaces of each glass plate, ion exchange treatment was performed. The ion exchange treatment was performed by immersing in KNO ₃ molten salt at 430 ° C. for 4 hours. After the ion exchange treatment, the glass surface of each glass plate is washed, and the compressive stress value CS of the surface compressive stress layer is determined from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho) and the interval between them. The stress depth DOL was calculated. In the calculation, the refractive index of each glass plate was set to 1.50, and the optical elastic constant was set to 30 [(nm / cm) / MPa].

  The volume resistivity ρa after the ion exchange treatment is a value measured at 150 ° C. based on ASTM C657-78 using a plate-like sample having a thickness of 0.7 mm as a measurement sample.

  The ratio R of the volume resistivity before and after the ion exchange treatment is calculated by the formula ρa / ρb.

  In addition, although the glass composition of a glass surface layer fluctuates microscopically before and after an ion exchange process, when it sees as the whole glass, you may think that a glass composition is substantially the same.

  Table 2 shows an example (sample No. 1 to 4) and a comparative example (sample No. 5) of the present invention.

  About the glass which has the glass composition of the sample A, after re-forming the dice-like glass into a spherical shape, the glass surface was polished under various conditions to obtain spherical glasses (Sample Nos. 1 to 5) shown in Table 2. Table 2 shows the diameter of the obtained spherical glass and its dimensional tolerance.

  The diameter of the spherical glass and its dimensional tolerance are values measured by a contact type length measuring machine. Specifically, the diameter of the spherical glass is obtained by measuring at least 10 diameters while rotating the glass and using the average value as a measurement value. The calculation of the average value is based on JIS B1563: 2009. ing. And the dimensional tolerance of the diameter was calculated from the measured value at this time. The measuring force of the indenter at the time of measurement is less than 3N.

Subsequently, the spherical glass was fixed to wire mesh jig, was immersed in KNO ₃ molten salt, a spherical glass was ion-exchanged to obtain glass rolling elements. The temperature of the KNO ₃ molten salt was 380 ° C., and the ion exchange treatment time was 72 hours.

The glass rolling element was taken out from the KNO ₃ molten salt and cooled in a room temperature atmosphere, and then the glass surface was washed with an alkaline detergent, pure water, alcohol or the like to remove the KNO ₃ molten salt adhering to the glass surface.

  Next, the diameter and dimensional tolerance of each sample after the ion exchange treatment were measured. In addition, the diameter of each sample after an ion exchange process and its dimensional tolerance are measured by said method.

  Subsequently, sample No. About 1-4, the glass surface was precision-polished and the diameter and dimensional tolerance of the obtained glass rolling element were evaluated by the said method. In addition, sample No. after ion exchange treatment. About 5, the glass surface is not grind | polished.

  The surface roughness Ra of the glass rolling element is measured by a method based on JIS B0601: 2001.

  As can be seen from Table 2, sample no. Nos. 1 to 4 had high dimensional accuracy because they were each subjected to a polishing step before and after the ion exchange treatment. Therefore, sample no. 1-4 are considered suitable for members located between the inner ring and the outer ring of a bearing device such as a bearing. On the other hand, sample No. No. 5 had low dimensional accuracy because it did not undergo a polishing step after the ion exchange treatment.

  The glass rolling element produced according to the present invention is particularly suitable for a member positioned between an inner ring and an outer ring of a bearing device such as a bearing, and is also applicable to a lens ball and a play ball.

Claims (12)

  A first polishing step for polishing the glass surface of the spherical glass, an ion exchange treatment step for obtaining a glass rolling element having a surface compressive stress layer by ion exchange treatment of the spherical glass after the first polishing step, and ion exchange treatment A method for producing a glass rolling element, comprising: a second polishing step for polishing the glass surface of the glass rolling element after the step.   The method for producing a glass rolling element according to claim 1, wherein the glass surface of the spherical glass is polished so that the dimensional tolerance of the diameter is within 0.01%.   The method for producing a glass rolling element according to claim 1 or 2, wherein the glass surface of the glass rolling element is polished so that a dimensional tolerance of the diameter is within 0.01%.   The method for producing a glass rolling element according to claim 1, wherein the glass surface of the spherical glass is polished so that the difference between lots is within 1 μm.   The method for producing a glass rolling element according to any one of claims 1 to 4, wherein the glass surface of the glass rolling element is polished so that the difference between lots is within 1 µm.   The glass rolling element according to claim 1, wherein the glass surface of the glass rolling element is polished so as to have a polishing width of 2 to 50% of the stress depth DOL of the surface compressive stress layer. Manufacturing method.   The method for producing a glass rolling element according to any one of claims 1 to 6, wherein the glass surface of the glass rolling element is polished so that the surface roughness Ra of the glass surface is 5 nm or less.   The method for producing a glass rolling element according to any one of claims 1 to 7, wherein the glass surface of the glass rolling element is polished so that the compressive stress value CS of the surface compressive stress layer is 100 MPa or more. The glass rolling element is made of glass containing, as a glass composition, SiO ₂ 45 to 75%, Al ₂ O ₃ 10 to 30%, Na ₂ O 5 to 25% by mass%. The manufacturing method of the glass rolling element in any one of -8. The method for producing a glass rolling element according to claim 1, wherein the glass rolling element is made of glass having a liquidus viscosity of 10 ^4.0 dPa · s or more. The method for producing a glass rolling element according to any one of claims 1 to 10, wherein the spherical glass is subjected to an ion exchange treatment by immersing it in KNO ₃ molten salt.   The ion exchange treatment is performed so that the compressive stress value CS of the surface compressive stress layer of the glass rolling element is 300 MPa or more and the stress depth DOL is 30 µm or more. Manufacturing method of glass rolling element.