JP2019001666A - Production method of glass rolling element, and glass rolling element - Google Patents

Abstract

To devise a method capable of producing a glass rolling element having high mechanical strength, and hardly being ruptured into pieces under a high load.SOLUTION: A production method of a glass rolling element includes a polishing step for polishing a glass surface of spherical glass, and an ion-exchange treatment step for obtaining the glass rolling element having a surface compressive stress layer by performing a plurality of times of the ion-exchange treatment to the spherical glass after the polishing step.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a glass rolling element and a glass rolling element, and particularly relates to a method for producing a glass rolling element and a glass rolling element that have high mechanical strength and are difficult to break apart under high load.

  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 a feature that it can be easily formed and processed into a spherical shape. 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 the stress depth DOL of the surface compressive stress layer of the glass rolling element is large, the mechanical strength of the glass rolling element is improved, but the glass rolling element may burst into pieces under a high load.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to devise a method capable of producing a glass rolling element that has high mechanical strength and is difficult to break apart under high load.

  As a result of various studies, the present inventor has found that the above technical problem can be solved by performing ion exchange treatment on a spherical glass a plurality of times, and proposes the present invention. That is, the method for producing a glass rolling element of the present invention comprises a polishing step for polishing a glass surface of a spherical glass, and a surface compression stress layer by performing ion exchange treatment a plurality of times on the spherical glass after the polishing step. An ion exchange treatment step of obtaining a glass rolling element having

  The manufacturing method of the glass rolling element of this invention is equipped with the grinding | polishing process which grind | polishes the glass surface of spherical glass. Thereby, the dimensional accuracy of a glass rolling element can be raised. On the other hand, when the glass surface of the spherical glass is polished, polishing scratches remain on the glass surface. Therefore, when the glass rolling element is incorporated in a bearing device or the like, it was used under severe conditions such as high-speed rotation, high friction, and high load. Sometimes, the glass rolling element may be damaged starting from a polishing scratch. Then, the manufacturing method of the glass rolling element of this invention is equipped with the ion exchange process process which obtains a glass rolling element by ion-exchange-processing spherical glass after a grinding | polishing process. Thereby, since a surface compressive-stress layer is formed in a glass rolling element, the mechanical strength of a glass rolling element can be raised.

  On the other hand, when the stress depth DOL of the surface compressive stress layer of the glass rolling element is increased in order to increase the mechanical strength of the glass rolling element, the tensile stress CT inside the glass rolling element becomes excessively high. As a result, there is a possibility that the glass rolling element bursts into pieces under a high load. Then, the manufacturing method of the glass rolling element of this invention is characterized by performing ion exchange process in multiple times with respect to the spherical glass after a grinding | polishing process. In this way, a glass rolling element having a high compressive stress value CS of the surface compressive stress layer and a deep stress depth DOL but a low internal tensile stress CT can be produced. As a result, it is possible to prevent the glass rolling element from being shattered under high load while maintaining high mechanical strength.

  Moreover, the manufacturing method of the glass rolling element of this invention is bending the compressive-stress curve in the depth direction from the glass surface by performing the ion exchange process in multiple times with respect to the spherical glass after a grinding | polishing process. A glass rolling element is obtained. In this way, a glass rolling element having a high compressive stress value CS of the surface compressive stress layer and a deep stress depth DOL but a low internal tensile stress CT can be produced. As a result, it is possible to prevent the glass rolling element from being shattered under high load while maintaining high mechanical strength.

  Moreover, it is preferable that the manufacturing method of the glass rolling element of this invention performs twice ion-exchange process with respect to the spherical glass after a grinding | polishing process.

  Moreover, it is preferable that the manufacturing method of the glass rolling element of this invention is equipped with the heat treatment process which heat-processes spherical glass after the 1st ion exchange process and before the 2nd ion exchange process.

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

In the method for producing glass rolling elements of the present invention, the glass rolling element, as a glass composition, in _{mol%, SiO 2 50~80%, Al} 2 O 3 5~30%, a Na 2 O 5 to 25% It is preferable to consist of the glass to contain.

  Moreover, in the manufacturing method of the glass rolling element of this invention, it is preferable that the compressive stress value CS of the surface compressive stress layer of a glass rolling element is 350 Mpa or more, and the stress depth DOL is 20 micrometers or more. Here, “the bending of the compressive stress curve in the depth direction from the glass surface”, “compressive stress value CS”, and “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.

  The glass rolling element of the present invention is a glass rolling element having a spherical shape, having a diameter tolerance within 0.01%, a surface compressive stress layer by ion exchange, and a depth from the glass surface. The compressive stress curve in the direction is bent.

The glass rolling elements of the present invention, as a glass composition, in _{mol%, SiO 2 50~80%, Al} 2 O 3 5~30%, preferably contains Na 2 O 5~25%.

  The glass rolling element of the present invention preferably has a compressive stress value CS of the surface compressive stress layer of 350 MPa or more and a stress depth DOL of 20 μm or more.

  As described above, the method for producing a glass rolling element according to the present invention includes a polishing step for polishing a glass surface of a spherical glass, and surface compression by performing ion exchange treatment multiple times on the spherical glass after the polishing step. An ion exchange treatment step of obtaining a glass rolling element having a stress layer. 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 contains, as a glass composition, mol%, SiO ₂ 50 to 80%, Al ₂ O ₃ 5 to 30%, and Na ₂ O 5 to 25%. It is preferable not to contain As ₂ O ₃ , Sb ₂ O ₃ and PbO. 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 mol% unless there is particular notice.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is preferably 50 to 80%, 55 to 77%, 57 to 75%, 58 to 74%, 60 to 73%, particularly 62 to 72%. If the content of SiO ₂ is too small, vitrification becomes difficult, and the thermal expansion coefficient becomes too high, so that the thermal shock resistance tends to decrease. On the other hand, if the content of SiO ₂ is too large, the meltability and the formability tends to decrease.

Al ₂ O ₃ is a component that improves ion exchange performance, and is a component that increases the strain point and Young's modulus. The content of Al ₂ O ₃ is preferably 5 to 30%. When the content of Al ₂ O ₃ is too small, resulting is a possibility which can not be sufficiently exhibited ion exchange performance. Therefore, the preferable lower limit range of Al ₂ O ₃ is 5.5% or more, 6.5% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, particularly 13% or more. . On the other hand, when the content of Al ₂ O ₃ is too large, devitrification crystal glass becomes easy to precipitate, hardly spherically shaped glass. Moreover, acid resistance also falls and it becomes difficult to apply to an acid treatment process. Therefore, the preferable upper limit range of Al ₂ O ₃ is 25% or less, 20% or less, 18% or less, 16% or less, 15% or less, particularly 14% or less.

Na ₂ O is an ion exchange component, and is a component that lowers the high temperature viscosity and improves the meltability and moldability. Na ₂ O is also a component that improves devitrification resistance. When Na 2 _O content is too small, or reduced meltability, lowered coefficient of thermal expansion tends to decrease the ion exchange performance. Therefore, the preferable lower limit range of Na ₂ O is 5% or more, 7% or more, more than 7.0%, 8% or more, particularly 9% or more. On the other hand, when the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance is lowered, there is a tendency that the density is high. In addition, the strain point may be excessively lowered or the component balance of the glass composition may be lost, and the devitrification resistance may be deteriorated. Therefore, the preferable upper limit range of Na ₂ O is 25% or less, 23% or less, 21% or less, 19% or less, 18.5% or less, 17.5% or less, 17% or less, 16% or less, 15.5 % Or less, 14% or less, 13.5% or less, particularly 13% or less.

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

The content of B ₂ O ₃ is preferably 0 to 15%. B ₂ O ₃ is a component that reduces high temperature viscosity and density, stabilizes the glass, makes it difficult to precipitate crystals, and lowers the liquidus temperature. Moreover, it is a component which raises crack resistance and raises scratch resistance. Therefore, the preferable lower limit range of B ₂ O ₃ is 0.01% or more, 0.1% or more, 0.5% or more, 0.7% or more, 1% or more, 2% or more, particularly 3% or more. . However, when the content of B ₂ O ₃ is too large, coloring of the glass surface called burnt occurs due to ion exchange, water resistance is lowered, and the stress depth DOL tends to be shallow. Therefore, the preferable upper limit range of B ₂ O ₃ is 14% or less, 13% or less, 12% or less, 11% or less, less than 10.5%, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, especially 4.9% or less.

Li ₂ O is an ion exchange component, and is a component that lowers the high-temperature viscosity to increase the meltability and moldability, and also increases the Young's modulus. Further, Li ₂ O has a large effect of increasing the compressive stress value CS among alkali metal oxides. However, in a glass system containing Na ₂ O of 7% or more, when the Li ₂ O content is extremely increased, the compression is rather reduced. The stress value CS tends to decrease. Further, when the content of Li 2 _O is too large, and decreases the liquidus viscosity, in addition to the glass tends to be devitrified, the thermal expansion coefficient becomes too high, the thermal shock resistance may decrease, It becomes difficult to match the thermal expansion coefficient of the surrounding material. Furthermore, the low-temperature viscosity is excessively decreased, and stress relaxation is likely to occur, and the compressive stress value CS may be decreased. Therefore, a suitable upper limit range of Li ₂ O is 2% or less, 1.7% or less, 1.5% or less, 1% or less, less than 1.0%, 0.5% or less, 0.3% or less, It is 0.2% or less, particularly 0.1% or less. Incidentally, when adding Li ₂ O, the preferred amount is 0.005% or more, 0.01% or more, particularly 0.05% or more.

K ₂ O is a component that promotes ion exchange, and is a component that easily increases the stress depth DOL among alkali metal oxides. Moreover, it is a component which reduces high temperature viscosity and improves a meltability and a moldability. Furthermore, it is also a component that improves devitrification resistance. However, when the content of K 2 _O is too large, the thermal expansion coefficient becomes too high, the thermal shock resistance tends to decrease. Moreover, there is a tendency that the strain point is excessively lowered, the component balance of the glass composition is lacking, and the devitrification resistance is lowered. Therefore, the preferable upper limit range of K ₂ O is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2.5% or less, particularly Less than 2%. Incidentally, when adding _{K 2} O, the preferred amount is 0.1% or more, 0.5% or more, particularly 1% or more. In the case to avoid the addition of _{K 2} O as much as possible, from 0 to 1.9%, from 0 to 1.35%, 0 to 1%, less than 0 to 1%, in particular from 0 to 0.05% is preferable .

When _{Li 2 O + Na 2 O +} K content of ₂ O is too small, the ion exchange performance and meltability is liable to decrease. On the other hand, when the content of _{Li 2 O + Na 2 O +} K 2 O is too large, too high thermal expansion coefficient, or the thermal shock resistance becomes liable to lower, there is a tendency that the density is high. Moreover, there is a tendency that the strain point is excessively lowered, the component balance of the glass composition is lacking, and the devitrification resistance is lowered. Therefore, the preferred lower limit range of Li ₂ O + Na ₂ O + K ₂ O is 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, particularly 12% or more, Suitable upper limit ranges are 30% or less, 25% or less, 20% or less, 19% or less, 18.5% or less, 17.5% or less, 16% or less, 15.5% or less, 15% or less, 14.5 % Or less, particularly 14% or less. “Li ₂ O + Na ₂ O + K ₂ O” is the total amount of Li ₂ O, Na ₂ O and K ₂ O.

  MgO is a component that lowers the viscosity at high temperature, increases meltability and moldability, and increases the strain point and Young's modulus. Among alkaline earth metal oxides, MgO is a component that has a large effect of improving ion exchange performance. is there. Therefore, the preferable lower limit range of MgO is 0% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, 4% or more, especially 4. 5% or more. However, when there is too much content of MgO, a density and a thermal expansion coefficient will become high easily and there exists a tendency for glass to devitrify easily. Therefore, the preferable upper limit range of MgO is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, particularly 5% or less.

  Compared with other components, CaO has a large effect of lowering the high temperature viscosity and improving the meltability and moldability, and increasing the strain point and Young's modulus without deteriorating devitrification resistance. However, if the content of CaO is too large, the density and thermal expansion coefficient become high, and the balance of the composition of the glass composition is lacking. On the contrary, the glass is liable to devitrify, the ion exchange performance is lowered, or the ion exchange. There is a tendency to easily deteriorate the solution. Therefore, suitable content of CaO is 0-6%, 0-5%, 0-4%, 0-3.5%, 0-3%, 0-2%, 0-1%, especially 0-0. .5%.

  SrO is a component that lowers the viscosity at high temperature to increase meltability and moldability, and increases the strain point and Young's modulus. However, if its content is too large, the ion exchange reaction tends to be inhibited. As a result, the density and the coefficient of thermal expansion increase, and the glass tends to devitrify. Therefore, the preferred content of SrO is 0 to 1.5%, 0 to 1%, 0 to 0.5%, 0 to 0.1%, particularly 0 to less than 0.1%.

  BaO is a component that lowers the high-temperature viscosity to increase the meltability and moldability, and increases the strain point and Young's modulus. However, when there is too much content of BaO, an ion exchange reaction will become easy to be inhibited, and also a density and a thermal expansion coefficient will become high, or glass will become devitrified easily. Therefore, suitable content of BaO is 0-6%, 0-3%, 0-1.5%, 0-1%, 0-0.5%, 0-0.1%, especially 0-0. Less than 1%.

  When there is too much content of MgO + CaO + SrO + BaO, there exists a tendency for a density and a thermal expansion coefficient to become high, for glass to devitrify, or for ion exchange performance to fall. Therefore, the preferable content of MgO + CaO + SrO + BaO is 0 to 9.9%, 0 to 8%, 0 to 7%, 0 to 6.5%, 0 to 6%, 0 to 5.5%, particularly 0 to 5%. It is. “MgO + CaO + SrO + BaO” is the total amount of MgO, CaO, SrO and BaO.

TiO ₂ is a component that enhances ion exchange performance and a component that lowers the high-temperature viscosity. However, if its content is too large, the glass tends to be colored or devitrified. Therefore, the content of TiO ₂ is 0 to 4.5%, 0 to 1%, 0 to 0.5%, 0 to 0.3%, 0 to 0.1%, 0 to 0.05%, particularly 0. -0.01% is preferred.

ZrO ₂ is a component that remarkably improves the ion exchange performance and a component that increases the viscosity and strain point in the vicinity of the liquid phase viscosity. Therefore, the preferable lower limit range of ZrO ₂ is 0.001% or more, 0.005% or more, 0.01% or more, particularly 0.05% or more. However, when the content of ZrO ₂ is too large, the devitrification resistance is remarkably lowered, the crack resistance may be lowered, and the density may be too high. Therefore, the preferable upper limit range of ZrO ₂ is 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, 0.3% or less, particularly 0.1% or less. .

  ZnO is a component that enhances the ion exchange performance, and is a component that is particularly effective in increasing the compressive stress value CS. Moreover, it is a component which reduces high temperature viscosity, without reducing low temperature viscosity. However, if the content of ZnO is too large, the glass tends to undergo phase separation, the devitrification resistance decreases, the density increases, or the stress depth DOL decreases. Therefore, the content of ZnO is preferably 0 to 6%, 0 to 5%, 0 to 3%, particularly preferably 0 to 1%.

P ₂ O ₅ is a component that enhances ion exchange performance, and in particular is a component that increases the stress depth DOL. However, when the content of P ₂ O ₅ is too large, or glass phase separation, the water resistance tends to decrease. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, 0 to 3%, 0 to 1%, 0 to 0.5%, particularly preferably 0 to 0.1%.

As a clarifier, one or more selected from the group of Cl, SO ₃ and CeO ₂ (preferably a group of Cl and SO ₃ ) may be added in an amount of 0 to 3%.

SnO ₂ has an effect of improving ion exchange performance. Therefore, the SnO ₂ content is preferably 0 to 3%, 0.01 to 3%, 0.05 to 3%, particularly 0.1 to 3%, and particularly preferably 0.2 to 3%.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus. However, the cost of the raw material itself is high, and when it is added in a large amount, the devitrification resistance tends to be lowered. Therefore, the rare earth oxide content is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less.

The tempered glass of the present invention preferably contains substantially no As ₂ O ₃ , Sb ₂ O ₃ , or PbO as a glass composition from the environmental consideration. Moreover, environmental considerations, it is also preferable to contain substantially no _Bi 2 _O 3, F. Here, “substantially does not contain” refers to a case where the content of the explicit component is less than 0.01 mol%.

  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. 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 “strain point” can be measured by the method of ASTM C336.

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 “temperature corresponding to a high temperature viscosity of 10 ^2.5 dPa · s” can be measured by a platinum ball pulling method.

  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. Note that the “liquid phase temperature” is obtained by passing the standard sieve 30 mesh (mesh opening 500 μm) and putting the glass powder remaining at 50 mesh (mesh opening 300 μm) into a platinum boat and holding it in a temperature gradient furnace for 24 hours. The value at which the temperature at which crystals precipitate is measured.

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. The “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by a platinum ball pulling method.

When the liquidus temperature is 1200 ° C. or less and the liquidus viscosity is 10 ^4.0 dPa · s or more, 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 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 the spherical glass while rotating it is preferable for reducing the dimensional tolerance of the diameter.

  In the polishing process, 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%, It is preferable to polish the glass surface of the spherical glass. When the dimensional tolerance of the diameter of the spherical glass is too large, the dimensional accuracy of the glass rolling element is difficult to decrease after the ion exchange treatment.

  In the 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, 4 mm or more, In particular, it is preferable to polish the glass surface of the spherical glass so as to be 5 mm or more. If it does in this way, it will become easy to apply to 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 has a surface compressive-stress layer by performing the ion exchange process in multiple times with respect to the spherical glass after a grinding | polishing process.

The ion exchange solution used for the ion exchange treatment is preferably a LiNO ₃ molten salt, a NaNO ₃ molten salt, a KNO ₃ molten salt, or a mixed molten salt thereof from the viewpoint of efficiently forming a surface compressive stress layer.

  In the manufacturing method of the glass rolling element of this invention, it is preferable to perform an ion exchange process twice with respect to spherical glass. Thereby, the compression stress curve in the depth direction from the glass surface can be bent without unduly reducing the efficiency of the ion exchange treatment step. In the present invention, the case where the ion exchange treatment is performed three times or more is not excluded.

  When the ion exchange treatment is performed twice, the ratio of small alkali ions (for example, Li ions, Na ions, particularly Na ions) in the ion exchange solution used for the second ion exchange treatment is the ion used for the first ion exchange treatment. Preferably less than that in the exchange solution. Thereby, it becomes easy to raise the density | concentration of the big alkali ion in the outermost surface, forming stress depth DOL deeply. The size of the alkali ions is Li ion <Na ion <K ion <Ce ion <Rb ion.

The content of LiNO ₃ in the ion exchange solution used for the first ion exchange treatment is preferably 1% by mass or less, 0.5% by mass or less, particularly 0.1% by mass or less. The content of LiNO ₃ in the ion exchange solution used for the second ion exchange treatment is preferably 1% by mass or less, 0.5% by mass or less, particularly 0.1% by mass or less. When there is too much LiNO ₃ in the ion exchange solution, it becomes difficult to form a surface compressive stress layer in the ion exchange treatment step.

The content of KNO ₃ in the ion exchange solution used for the first ion exchange treatment is preferably less than 85% by mass, 82% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, and 50% by mass. Hereinafter, it is 40 mass% or less especially. If the content of KNO ₃ in the ion exchange solution is too large, the compressive stress in the deep portion of the surface compressive stress layer becomes too high, and the internal tensile stress CT may become excessive. The content of NaNO ₃ in the ion exchange solution used for the first ion exchange treatment is preferably 15% by mass or more, 18% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, and 50% by mass. % Or more, particularly 60% by mass or more. If the content of NaNO ₃ is too small, the compressive stress in the deep part of the surface compressive stress layer becomes too high, and the internal tensile stress CT may become excessive. The upper limit of the content of NaNO ₃ is not particularly limited, but is substantially 95% by mass or less, 90% by mass or less, 80% by mass or less, and particularly 70% by mass or less.

The content of KNO ₃ in the ion exchange solution used for the second ion exchange treatment is preferably 98% by mass or more, 99% by mass or more, 99.2% by mass or more, 99.4% by mass or more, 99.6% by mass. % Or more, 99.8% by mass or more, and 99.9 to 100% by mass. Thereby, it becomes easy to raise the compressive stress of the glass surface vicinity.

The content of NaNO _{3 in} the ion exchange solution used for the second ion exchange treatment is 1% by mass or more, 3% by mass or more than the content of NaNO ₃ in the ion exchange solution used for the first ion exchange treatment, 5% by mass or more, 7% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, and particularly preferably 40% by mass or less. This makes it easy to increase the compressive stress value CS by the second ion exchange process.

  The second ion exchange temperature is preferably 10 ° C. or more, 20 ° C. or more, 30 ° C. or more, 40 ° C. or more, and particularly 50 ° C. or more lower than the first ion exchange temperature. The first ion exchange temperature is 413 ° C. or higher, 420 ° C. or higher, 430 ° C. or higher, particularly 440 to 500 ° C., and the second ion exchange temperature is preferably 350 to 410 ° C., particularly 360 to 400 ° C. Thereby, the stress depth DOL is increased by the first ion exchange treatment, and the compressive stress value CS is easily increased by the second ion exchange treatment.

  The second ion exchange time is preferably shorter than the first ion exchange time by 2 hours or more, 3 hours or more, 4 hours or more, particularly 5 hours or more. The first ion exchange time is 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, particularly 7 to 10 hours, and the second ion exchange time is 5 to 200 minutes, 10 to 180 minutes, 15 hours. -150 minutes, especially 30-130 minutes are preferred. Thereby, the stress depth DOL is increased by the first ion exchange treatment, and the compressive stress value CS is easily increased by the second ion exchange treatment.

  The compressive stress value CS of the surface compressive stress layer of the glass rolling element is preferably 350 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, latent scratches are likely to occur on the glass surface after the ion exchange treatment step. Moreover, there exists a possibility that the tensile stress CT inherent in a glass rolling element may become extremely high. Therefore, the compressive stress value CS of the surface compressive stress layer is preferably 1800 MPa or less. Note that the compression stress value CS can be increased by shortening the ion exchange time of the second ion exchange process or lowering the ion exchange temperature (temperature of the ion exchange solution).

  The stress depth DOL of the surface compressive stress layer of the glass rolling element is preferably 20 μm or more, 30 μm or more, 40 μm or more, and particularly 50 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 CT inherent in the glass rolling element may be unduly high. Therefore, the stress depth DOL is preferably 300 μm or less, 200 μm or less, particularly 150 μm or less. Note that the stress depth DOL can be increased by increasing the ion exchange time of the first ion exchange treatment or increasing the ion exchange temperature.

  In the manufacturing method of the glass rolling element of this invention, you may provide the heat treatment process which heat-processes spherical glass after the first ion exchange process and before the second ion exchange process. In this way, since the ion exchange reaction proceeds by heat treatment, the compressive stress curve in the depth direction from the glass surface can be bent even if the first and second ion exchange solutions are the same. As a result, the cost and efficiency of the ion exchange process can be increased. The heat treatment temperature is preferably 300 to 600 ° C., particularly 350 to 500 ° C. in order to advance the ion exchange reaction while suppressing thermal deformation of the spherical glass.

  From the viewpoint of the production efficiency of the glass rolling element, the ion exchange treatment is preferably performed simultaneously on a plurality of spherical glasses. In this case, the mesh width is larger than the diameter of the spherical glasses so that the spherical glasses do not contact each other. More preferably, a plurality of spherical glasses are arranged at equal intervals on a small metal jig or the like, and the ion exchange treatment is performed in a state where the jigs are laminated. Further, it is preferable to perform the ion exchange treatment while rotating or vibrating the spherical glass. By doing so, the variation in characteristics of the surface compressive stress layer on the glass surface is reduced, so that the dimensional accuracy of the glass rolling element can be increased.

  In the method for producing a glass rolling element of the present invention, a polishing step may be provided after the ion exchange treatment step in order to increase dimensional accuracy, and in order to reduce or eliminate polishing scratches and latent scratches on the glass surface, an ion exchange treatment is performed. A polishing step may be provided after the step. Moreover, you may provide a washing | cleaning process before and after a grinding | polishing process and an ion exchange process.

  The glass rolling element of the present invention is a glass rolling element having a spherical shape, having a diameter tolerance within 0.01%, a surface compressive stress layer by ion exchange, and a depth from the glass surface. Although the compressive stress curve in the direction is bent, a part of this technical feature has already been described, and a detailed description thereof will be omitted.

  In the glass rolling element of the present invention, the dimensional tolerance of the diameter is preferably within 0.01%, within 0.005%, within 0.003%, within 0.002%, within 0.0015%, particularly preferably 0.001. %. When the dimensional tolerance of the diameter of the spherical glass is too large, the dimensional accuracy of the glass rolling element is difficult to decrease after the ion exchange treatment.

In the glass rolling element of the present invention, the degree of change (−dn / dx) [mol% / μm] relative to the depth (x) direction of the K ₂ O concentration (n) is preferably 5 μm deep from the outermost surface. Is 0.15 or more, 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.37 or more, 0.39 or more, 0.41 or more, and further 0.43 to 5.0, Particularly, they are 0.44 to 4.0 and 0.45 to 3.5. If the degree of change (−dn / dx) in the depth (x) direction of the K ₂ O concentration (n) is too small at a depth of 5 μm from the outermost surface, the compressive stress value CS of the surface compressive stress layer tends to decrease. Or the internal tensile stress CT tends to be excessive.

The degree of change (−dn / dx) [mol% / μm] with respect to the depth (x) direction of the K ₂ O concentration (n) is preferably at a depth of 20 μm from the outermost surface, preferably less than 0.22, 20 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, particularly 0.04 to 0.14. If the degree of change (−dn / dx) in the depth (x) direction of the K ₂ O concentration (n) is too large at a depth of 20 μm from the outermost surface, the stress depth DOL of the surface compressive stress layer tends to be shallow. .

The degree of change (−dn / dx) [mol% / μm] with respect to the depth (x) direction of the K ₂ O concentration (n) is preferably less than 0.15 at a depth of 35 μm from the outermost surface. 13 or less, 0.11 or less, 0.09 or less, 0.08 or less, 0.07 or less, and particularly 0.01 to 0.06. If the degree of change (−dn / dx) in the depth (x) direction of the K ₂ O concentration (n) is too large at a depth of 35 μm from the outermost surface, the internal tensile stress CT tends to be excessive, and the surface The stress depth DOL of the compressive stress layer tends to be shallow.

The difference between the K _{2 O} concentration in the deepest part of the K _{2 O} concentration and the surface compressive stress layer on the outermost surface of the surface compressive stress layer is preferably 5 mol% or more, 6 mol%, 7 mol%, particularly 8 to 11 mol%. When the difference between the K _{2 O} concentration in the deepest part of the K _{2 O} concentration and the surface compressive stress layer on the outermost surface of the surface compressive stress layer is too small, the compression stress value CS of the surface compressive stress layer is liable to lower, also stresses The depth DOL tends to be shallow.

Integral value of K _{2 O} concentration in the difference between the K _{2 O} concentration in the deepest part of the K _{2 O} concentration and the surface compressive stress layer on the outermost surface of the surface compressive stress layer (∫ndx) is preferably less than 165 mol% · [mu] m 160 mol% · μm or less, 155 mol% · μm or less, 150 mol% · μm or less, 148 mol% · μm or less, particularly 80 to 145 mol% · μm. When the integral value of the K _{2 O} concentration in the difference between the K _{2 O} concentration in the deepest part of the K _{2 O} concentration and the surface compressive stress layer at the outermost surface is too large surface compressive stress layer, the internal tensile stress CT becomes excessive easy. Incidentally, _{K 2} O concentration profiles (outermost surface of the _{K 2} O concentration of the "surface compressive stress layer, _{K 2} O concentration in the deepest portion, the integral value of the _{K 2} O concentration from the outermost surface to the deepest ∫Ndx, depth change degree in the depth direction of the K _{2 O} concentration in the 5 [mu] m, the change of the depth direction of the K _{2 O} concentration in the depth 20 [mu] m, the change in the depth direction of the K _{2 O} concentration in the depth 35μm degree) " Prepares a glass plate having the same composition, the same thermal history, the same ion exchange treatment and the same surface composition profile as a spherical glass as a measurement sample, and a scanning electron microscope equipped with EDX (Hitachi High (S-4300SE manufactured by Technologies).

  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 compositions of Samples A to E are mol%, SiO ₂ 66.5%, Al ₂ O ₃ 11.5%, B ₂ O ₃ 0.5%, Na ₂ O 15.2%, K _2. O 1.4%, MgO 4.8%, SnO ₂ 0.2%, the glass composition of sample F is mol%, SiO ₂ 66.1%, Al ₂ O ₃ 13.0%, Na ₂ O 16 Glass raw materials were prepared so as to be 0.9%, MgO 3.8%, and SnO ₂ 0.1%, and melted at 1580 ° C. for 8 hours using a platinum container. Thereafter, the molten glass was poured out on the carbon plate and formed into a plate shape to obtain a glass plate. When various characteristics of the obtained glass plate were measured, Samples A to E had a density of 2.45 g / cm ³ , a thermal expansion coefficient α of 91.2 × 10 ⁻⁷ / ° C., and a strain point Ps of 564. , The annealing point Ta is 613 ° C., the softening point Ts is 863 ° C., the temperature at a high temperature viscosity of 10 ^4.0 dPa · s is 1255 ° C., the temperature at 10 ^3.0 dPa · s is 1460 ° C., 10 ^2.5 dPa The temperature at s was 1591 ° C., the liquid phase temperature TL was 970 ° C., and the liquid phase viscosity log η _TL was 6.3 dPa · s. Sample F has a density of 2.45 g / cm ³ , a thermal expansion coefficient α of 88 × 10 ⁻⁷ / ° C., a strain point Ps of 614 ° C., an annealing point Ta of 667 ° C., a softening point Ts of 915 ° C., and a high temperature viscosity. The temperature at 10 ^4.0 dPa · s is 1295 ° C., the temperature at 10 ^3.0 dPa · s is 1489 ° C., the temperature at 10 ^2.5 dPa · s is 1612 ° C., the liquidus temperature TL is 1013 ° C., the liquidus viscosity The log η _TL was 6.3 dPa · s.

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

  The thermal expansion coefficient α is a value obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. using a dilatometer.

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

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

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

  The liquid phase temperature TL passes through a standard sieve 30 mesh (a sieve opening of 500 μm), and glass powder remaining in a 50 mesh (a sieve opening of 300 μm) is put in a platinum boat, and then held in a temperature gradient furnace for 24 hours. This is a value obtained by measuring the temperature at which crystals are deposited.

The liquid phase viscosity log η _TL is a value obtained by measuring the viscosity of the glass at the liquid phase temperature by a platinum ball pulling method.

  Subsequently, about the said glass plate (plate thickness 0.7mm), the tempered glass plate (sample BF) was obtained by performing the ion exchange process on the ion exchange conditions shown in Table 1. Sample A is an unstrengthened glass plate that has not been subjected to ion exchange treatment. In addition, although the glass composition in the surface layer is microscopically different before and after the ion exchange treatment, the glass composition is hardly different when viewed as the whole glass.

The obtained tempered glass plate, compression stress value CS of the surface compressive stress layer was evaluated profile of stress depth DOL and K _{2 O} concentration. The results are shown in Table 2.

  The compressive stress value CS and the stress depth DOL of the surface compressive stress layer are determined from the number of interference fringes observed and their spacing when the sample is observed using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho). It is a calculated value. In the calculation, the refractive index of samples B to E is 1.50, the optical elastic constant is 29.5 [(nm / cm) / MPa], the refractive index of sample F is 1.50, and the optical elastic constant is 28. 0.8 [(nm / cm) / MPa].

_{K 2} O concentration of _{K 2} O concentration profiles (outermost surface of the surface compressive stress layer, _{K 2} O concentration in the deepest portion, the integral value of the _{K 2} O concentration from the outermost surface to the deepest ∫Ndx, at a depth 5μm change degree in the depth direction of the K ₂ O concentration, change degree in the depth direction of the _{K 2} O concentration in the depth 20 [mu] m, the change of the depth direction of the _{K 2} O concentration in the depth 35 [mu] m) is the EDX It is obtained by a scanning electron microscope (S-4300SE manufactured by Hitachi High-Technologies Corporation). Specifically, the measurement was performed at an interval of 2.5 μm in a region having a depth of 2.5 to 20 μm, and the measurement was performed at an interval of 5 μm in a region having a depth of 20 to 250 μm. And the measurement was performed at three different measurement points, and the average value was taken as the measurement value. Also the _{K 2} O concentration in the depth 2.5μm was _{K 2} O concentration in the outermost surface. Further, the depth at which no significant difference was recognized in the standard deviation of the K ₂ O concentration was taken as the deepest part. However, for sample F, since the K ₂ O concentration was below the detection limit at a depth of 60 μm, the measurement range was set to a depth of 60 μm.

For reference, the integral value ∫ndx (mol% · μm) of the K ₂ O concentration was calculated using a right-end type piecewise quadrature method (Riemann integration). In the section [0, 20], the strip width Δx was set to 2.5, and in the section [20, 250], the strip width Δx was set to 5. Specifically, for the area of the strip in the section [0, 2.5], the value of the K ₂ O concentration at the right end, that is, x = 2.5 was used. Assuming that the K ₂ O concentration at each measurement point x is f (x), the integral value in the section [0, 20] = ∫f (x) dx = 2.5 × (f (2.5) + f (5 0.0) + f (7.5) + f (10.0) + f (12.5) + f (15.0) + f (17.5) + f (20.0), where the depth of the K ₂ O concentration is The degree of change (−dn / dx) [mol% / μm] with respect to the vertical direction is obtained by plotting the K ₂ O concentration at each measurement depth with the table tabulation software EXCEL2010 manufactured by Microsoft, and approximating the mth order polynomial by the least square method. A curve (f (x) = αx ^m + βx ^m−1 +...) Was obtained and differentiated to obtain −f ′ (a) at each measurement point x = a from f ′ (x) as the degree of change. The degree of change at x = 5 is obtained by deriving a sixth-order (m = 6) polynomial approximate curve in the interval [2.5, 10] and differentiating it to obtain the tangent at x = 5. The degree of change was obtained by multiplying the slope of (-1) by an approximation curve from a quadratic (m = 2) polynomial approximation in the interval [15, 25] for the degree of change at x = 20, It calculated by calculating | requiring the inclination of the tangent in x = 25. About the change degree in x = 35, an approximated curve was derived | led-out from the quadratic (m = 2) polynomial approximation in area [30,45], and x = It calculated by calculating | requiring the inclination of the tangent in 35. In addition, it is -f '(a)> = 0.

  Separately, molten glass having the glass compositions of Samples D, E, and F was formed into a dice shape to obtain a dice glass, and then reshaped into a spherical glass. At the time of melting and forming, attention was paid so that the thermal history of the spherical glass was the same as that of the glass plates according to samples D, E, and F, respectively. In addition, when ion exchange processing is performed on these spherical glasses under the same ion exchange conditions, it is considered that the surface composition profile and the state of the surface compressive stress layer are the same.

  The glass surface of the spherical glass having the glass composition of Samples D, E, and F was polished to obtain a spherical glass. These spherical glasses had a diameter of 3.982 mm and a dimensional tolerance of 0.005%.

  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, after fixing the spherical glass to a wire mesh jig, the ion exchange treatment was performed twice under the same conditions as the ion exchange treatment for the samples D, E, and F shown in Table 1 while rotating the spherical glass. The glass rolling elements (samples D ′, E ′, F ′) were obtained.

  After the second ion exchange treatment, the glass rolling element is taken out from the ion exchange solution, cooled in a room temperature atmosphere, the glass surface is washed with an alkaline detergent, pure water, alcohol, etc., and the ion exchange solution adhered to the glass surface is removed. Removed.

As can be seen from Table 2, samples D ′, E ′, and F ′ have a high compressive stress value CS of the surface compressive stress layer and a deep stress depth DOL, but a small integrated value of the K ₂ O concentration, so that glass The compressive stress curve in the depth direction from the surface is bent, and the internal tensile stress CT is considered to be low. As a result, it is considered that the glass rolling element can be prevented from being shattered under high load while maintaining high mechanical strength.

  Assuming that the glass rolling elements (samples A ′, B ′, and C ′) were also produced for the samples A, B, and C in accordance with the above-described experiment, the sample A ′ has no surface compressive stress layer. It is estimated that the mechanical strength is low, the sample B ′ has a high internal tensile stress CT, and the sample C ′ has a low compressive stress value CS of the surface compressive stress layer.

  The glass rolling element of 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 (10)

  A polishing step for polishing the glass surface of the spherical glass, and an ion exchange treatment step for obtaining a glass rolling element having a surface compressive stress layer by performing ion exchange treatment a plurality of times on the spherical glass after the polishing step, A method for producing a glass rolling element, comprising:   A glass in which the compressive stress curve in the depth direction from the glass surface is bent by performing a plurality of ion exchange treatments on the spherical glass after polishing and polishing the glass surface of the spherical glass An ion exchange treatment step for obtaining a rolling element, and a method for producing a glass rolling element.   The method for producing a glass rolling element according to claim 1 or 2, wherein the ion exchange treatment is performed twice on the spherical glass after the polishing step.   The method for producing a glass rolling element according to any one of claims 1 to 3, further comprising a heat treatment step of heat treating the spherical glass after the first ion exchange treatment and before the second ion exchange treatment.   The method for producing a glass rolling element according to any one of claims 1 to 4, wherein the glass surface of the spherical glass is polished so that the dimensional tolerance of the diameter is within 0.01%. Glass rolling elements, as a glass composition, in _mol%, claim 1, characterized in that it consists of glass containing _{SiO 2 50~80%, Al 2 O} 3 5~30%, a Na 2 O 5 to 25% The manufacturing method of the glass rolling element in any one of -5.   The method for producing a glass rolling element according to claim 1, wherein the compressive stress value CS of the surface compressive stress layer of the glass rolling element is 350 MPa or more and the stress depth DOL is 20 μm or more.   A glass rolling element having a spherical shape, having a dimensional tolerance within 0.01%, having a surface compressive stress layer by ion exchange, and bending the compressive stress curve in the depth direction from the glass surface. A glass rolling element characterized by The glass rolling element according to claim 8, wherein the glass rolling element contains, as a glass composition, 50 to 80% of SiO ₂ , 5 to 30% of Al ₂ O _{3 and} 5 to 25% of Na ₂ O.   The glass rolling element according to claim 8 or 9, wherein the compressive stress value CS of the surface compressive stress layer is 350 MPa or more and the stress depth DOL is 20 µm or more.