阅读说明：本技术 玻璃球 (Glass ball ) 是由 小池章夫 胜田信 村山优 今北健二 于 2018-06-20 设计创作，主要内容包括：本发明提供一种轻质、具有绝缘性并且充分确保强度、而且其加工和制造比较容易、能够降低制造成本的玻璃球。一种玻璃球，其由玻璃材料形成，所述玻璃材料的密度为2.3g/cm<Sup>3</Sup>～3.2g/cm<Sup>3</Sup>，所述玻璃材料的杨氏模量为60GPa～150GPa，所述玻璃材料在50℃～350℃的范围内的平均热膨胀系数为40×10<Sup>?7</Sup>/℃～120×10<Sup>?7</Sup>/℃，以氧化物基准的摩尔百分率表示，所述玻璃材料含有：30摩尔％～75摩尔％的SiO<Sub>2</Sub>、2摩尔％～30摩尔％的Al<Sub>2</Sub>O<Sub>3</Sub>、5摩尔％～25摩尔％的R<Sub>2</Sub>O(其中，R为选自Li、Na、K中的一种以上)，并且所述玻璃球在表面具有压应力层。(The invention provides a glass ball which is light, has insulation property, fully ensures strength, is relatively easy to process and manufacture and can reduce the manufacturing cost. A glass sphere formed from a glass material having a density of 2.3g/cm 3 ～3.2g/cm 3 The Young's modulus of the glass material is 60 GPa-150 GPa, and the average thermal expansion coefficient of the glass material in the range of 50 ℃ to 350 ℃ is 40 multiplied by 10 ‑7 /℃～120×10 ‑7 /° c, expressed as mole percent on an oxide basis, the glass material comprising: 30 to 75 mol% of SiO 2 2 to 30 mol% of Al 2 O 3 5 to 25 mol% of R 2 O (wherein R is one or more selected from Li, Na and K), and the glass sphere has a compressive stress layer on the surface.)

1. A glass ball is characterized in that the glass ball is provided with a ball body,

the glass spheres are formed of a glass material,

the density of the glass material is 2.3g/cm³～3.2g/cm³，

The Young's modulus of the glass material is 60 GPa-150 GPa,

the average thermal expansion coefficient of the glass material in the range of 50-350 ℃ is 40 multiplied by 10^-7/℃～120×10^-7/℃，

The glass material contains, expressed in mole percent on an oxide basis: 30 to 75 mol% of SiO₂2 to 30 mol% of Al₂O₃5 to 25 mol% of R₂O (wherein, R is more than one selected from Li, Na and K),

the glass ball is provided with a compressive stress layer on the surface.

2. The glass sphere of claim 1, wherein the depth of compressive stress layer (DOL) is from 8 μ ι η to 500 μ ι η.

3. The glass sphere of claim 1 or 2, wherein the glass material is a Li-containing glass containing, expressed in mole percent on an oxide basis: 50 to 75 mol% of SiO₂4 to 20 mol% of Al₂O₃1 to 15 mol% of Li₂O, 5 to 25 mol% of R₂O (wherein R is at least one selected from Li, Na and K), 0 to 15 mol% of MgO, and 92 mol% or more of SiO₂+Al₂O₃+R₂O+MgO。

4. The glass sphere of claim 1 or 2, wherein the glass material is Y-containing₂O₃Glass, in moles based on oxidesExpressed in percentage, said contains Y₂O₃The glass contains: 30 to 70 mol% of SiO₂4 to 30 mol% of Al₂O₃5 to 20 mol% of Li₂O, 5 to 25 mol% of R₂O (wherein R is at least one selected from Li, Na and K), 1 to 25 mol% of MgO, and 1 to 20 mol% of Y₂O₃。

5. The glass sphere of any one of claims 1 to 4, wherein the glass sphere has a surface compressive stress value (CS)₀) 200MPa to 1500 MPa.

6. The glass sphere of any one of claims 1 to 5, wherein the glass sphere has a Vickers hardness (Hvct) of 6.0GPa or more.

7. The glass bead of any one of claims 1 to 6, wherein said glass bead has a diameter of 0.5mm to 100 mm.

Technical Field

The present invention relates to a glass ball, and more particularly to a glass ball suitable as a ball for a rolling bearing (ball bearing).

Background

A ball bearing for supporting a rotation shaft is generally installed at a driving part of various kinds of apparatuses. Conventionally, a ball made of metal such as steel has been widely used for a ball and a bearing used for such a ball bearing.

However, when a ball bearing is rotated at high speed, if heavy balls such as steel balls are used, a large centrifugal force is generated, and the bearing may be damaged. In response to this, a technique for manufacturing a hollow ball in order to reduce the weight is known (see patent document 1). On the other hand, when a ball bearing is used near an inverter motor or the like, if the ball is made of metal, a high-frequency current generated from the inverter motor may flow into the bearing, and the bearing may be damaged by the high-frequency current.

In response to this, a light-weight and insulating bearing ball is required, and a ball made of ceramics such as silicon nitride, which can be reduced in weight and has high strength, has been studied (see patent document 2).

Disclosure of Invention

Problems to be solved by the invention

As described above, ceramic balls are easy to be lighter in weight and have insulation properties compared to metal balls, and therefore, application to the inverter air conditioner can be sufficiently considered. However, ceramic balls, particularly silicon nitride balls, have very high hardness and are not easily processed. Therefore, when manufacturing a ball for a bearing that requires exactly a desired shape and size, labor and cost increase, and efficient production is difficult.

Accordingly, an object of the present invention is to provide a glass ball which is lightweight, has insulation properties, has sufficient strength, can be easily processed into a desired shape, can be easily manufactured, and has good productivity.

Means for solving the problems

The present inventors have made extensive studies and, as a result, have found that the above problems can be solved by using spherical bodies (glass spheres) made of glass having a predetermined composition and characteristics, and have completed the present invention.

That is, the glass beads of the present invention are characterized in that the glass beads are formed of a glass material having a density of 2.3g/cm³～3.2g/cm³The Young's modulus of the glass material is 60 GPa-150 GPa, and the average thermal expansion coefficient of the glass material in the range of 50 ℃ to 350 ℃ is 40 multiplied by 10^-7/℃～120×10^-7/° c, expressed as mole percent on an oxide basis, the glass material comprising: 30 to 75 mol% of SiO₂2 to 30 mol% of Al₂O₃5 to 25 mol% of R₂O (wherein R is one or more selected from Li, Na and K), and the glass sphere has a compressive stress layer on the surface.

Effects of the invention

According to the present invention, a glass ball that is lightweight, has insulation properties, and has sufficient strength can be provided. The glass ball is suitable as a ball for a ball bearing (particularly, a ball for a ball bearing used in a device having an inverter circuit). In addition, the glass ball is easy to manufacture, and the manufacturing cost can be reduced and the productivity can be improved.

Detailed Description

The glass ball of the present invention will be described in detail below with reference to embodiments, but the present invention is not limited to the following embodiments and can be arbitrarily modified and implemented within a range not departing from the gist of the present invention.

In the present specification, the "glass material" refers to glass before the strengthening treatment. "to" indicating a numerical range is used to include numerical values described before and after the range as a lower limit value and an upper limit value.

(first embodiment)

[ glass ball ]

The glass beads of the present embodiment have the above-described configuration, and are formed of a glass material having a density of 2.3g/cm³～3.2g/cm³The Young's modulus of the glass material is 60 GPa-150 GPa, and the average thermal expansion coefficient of the glass material in the range of 50 ℃ to 350 ℃ is 40 multiplied by 10^-7/℃～120×10^-7/° c, expressed as mole percent on an oxide basis, the glass material comprising: 30 to 75 mol% of SiO₂2 to 30 mol% of Al₂O₃5 to 25 mol% of R₂O (wherein R is one or more selected from Li, Na and K), and the glass sphere has a compressive stress layer on the surface.

< glass composition >

The glass composition of the glass material used in the present embodiment basically represents the glass composition before the strengthening treatment. When a chemical strengthening treatment is used as the strengthening treatment, the glass composition of the surface thereof slightly changes due to ion exchange. However, in general, even when a compressive stress layer is formed by chemical strengthening treatment, a portion having tensile stress (hereinafter, also referred to as a tensile stress portion) which is not strengthened in the compressive stress layer is mostly present, and even in a glass after the strengthening treatment, the composition of the tensile stress portion is the same as that of a glass before the strengthening treatment (glass composition of a glass material).

Here, the composition of the glass can be easily determined by semiquantitative analysis using a fluorescent X-ray method, and more accurately, can be measured by a wet analysis method such as ICP emission analysis. The content of each component is expressed by a mole percentage (mol%) based on the oxide, and is hereinafter expressed by "%" unless otherwise specified. Hereinafter, the constituent components will be specifically described with respect to the glass composition.

The glass material constituting the glass spheres of the present embodiment contains, as expressed by mole percentage based on oxides: 30 to 75 percent of SiO₂2 to 30 percent of Al₂O₃5% -25% of R₂O (wherein, R is more than one selected from Li, Na and K). The glass material used here is a material capable of forming a compressive stress layer on the glass surface by tempering treatment, and preferably a material capable of forming a compressive stress layer by chemical tempering treatment.

SiO₂Is a component constituting the skeleton of the glass. In addition, SiO₂Is a component for improving chemical durability and is a component for reducing the occurrence of cracks when scratches (indentations) are generated on the glass surface.

In order to effectively exhibit the above characteristics, the SiO₂The content of (A) is more than 30%. SiO 2₂The content of (b) is preferably 35% or more, more preferably 45% or more, further preferably 50% or more, and particularly preferably 60% or more. On the other hand, SiO₂When the content of (A) is more than 75%, the meltability tends to be lowered, and therefore, SiO₂The content of (b) is 75% or less, preferably 70% or less, more preferably 68% or less.

Al₂O₃Is a component for improving the Young's modulus and hardness, and is an essential component in the case of using as a ball for a ball bearing. In addition, Al₂O₃Is effective for improving the ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening. Further, Al₂O₃Is a component for raising the glass transition temperature (Tg) of the glass, and is also used for increasing the compressive stress during chemical strengtheningA component which is not easy to reduce the compressive stress even if the treatment is performed for a long time due to the depth of layer.

In order to effectively exhibit the above characteristics, Al₂O₃The content of (A) is more than 2%. Al (Al)₂O₃The content of (b) is preferably 2.5% or more. On the other hand, Al₂O₃When the content of (b) is more than 30%, the acid resistance of the glass tends to be lowered or the devitrification temperature tends to be increased, so that Al₂O₃The content of (B) is 30% or less. In addition, the viscosity of the glass may increase and the meltability may decrease. Thus, Al₂O₃The content of (b) is preferably 27% or less, more preferably 20% or less, further preferably 15% or less, and particularly preferably 10% or less.

R₂O (where R is one or more selected from Li, Na, and K) is a component for forming a surface compressive stress layer on the glass surface by ion exchange, and is a component for improving the crushability of the chemically strengthened glass. Total amount of these components (Li)₂O+Na₂O+K₂O) is 5% or more, preferably 8% or more, more preferably 10% or more, and further preferably 12% or more. In another aspect, R₂When the content of O is more than 25%, the acid resistance of the glass tends to decrease, and therefore, R is₂The content of O is 25% or less. R₂The content of O is preferably 20% or less, more preferably 18% or less.

Li₂O is a component useful for realizing a lightweight, insulating, and sufficiently strong glass sphere and increasing the young's modulus while keeping the density low. In addition, Li₂O is a component used when a surface compressive stress layer is formed on the glass surface by ion exchange, and improves the abrasion resistance of the glass. When the chemical strengthening treatment is performed by replacing Li ions on the glass surface with Na ions, Li is present₂The content of O is preferably 2% or more, more preferably 3% or more, further preferably 5% or more, and particularly preferably 7% or more. On the other hand, Li₂When the content of O is more than 20%, the acid resistance of the glass tends to decrease, and therefore, Li₂The content of O is preferably 20% or less, more preferably 17% or less.

Na₂O is a component that forms a surface compressive stress layer by ion exchange and improves the meltability of the glass. Although Na may not be contained₂O but due to Na₂O can promote the replacement of Li ions on the glass surface with Na ions, and therefore Na ions are contained in the glass₂Na in case of O₂The content of O is preferably 1% or more. Na (Na)₂The content of O is more preferably 2% or more, and still more preferably 3% or more. On the other hand, Na₂When the content of O is more than 8%, the surface compressive stress formed by ion exchange may be reduced. Na (Na)₂The content of O is preferably 8% or less, more preferably 7% or less, further preferably 6% or less, particularly preferably 5% or less, and most preferably 4% or less.

In the strengthening treatment, when Li ions and Na ions, Na ions and K ions on the glass surface are simultaneously ion-exchanged by a method such as immersing in a mixed molten salt of potassium nitrate and sodium nitrate, Na ions and K ions are added to the glass surface₂The content of O is more preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less. In addition, Na₂The content of O is preferably 2% or more, more preferably 3% or more, and further preferably 4% or more.

K may be contained for the purpose of improving ion exchange performance or the like₂And O. In the presence of K₂K in the case of O₂The content of O is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, and particularly preferably 3% or more. On the other hand, K₂When the content of O is more than 10%, the Young's modulus is lowered, so that K₂The content of O is preferably 10% or less. K₂The content of O is more preferably 8% or less, still more preferably 6% or less, particularly preferably 4% or less, and most preferably 2% or less.

In addition, the glass composition of the glass material may contain various optional components in addition to the above components within a range not to impair the effects of the present embodiment. Here, as optional components, for example, the following components can be mentioned.

B₂O₃Reduce brittleness of glass spheres and improve meltabilityThe composition of (1). B is₂O₃Is not an essential component, but contains B₂O₃In the case of (B), in order to improve the meltability, B₂O₃The content of (b) is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, B₂O₃When the content of (B) is more than 5%, the acid resistance is liable to deteriorate, so that B₂O₃The content of (b) is preferably 5% or less, more preferably 4% or less, and further preferably 3% or less. In addition, in order to prevent generation of a striae (pulse) during melting and to reduce the quality of glass, B₂O₃The content of (b) is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. Further, it is preferable that B is not substantially contained₂O₃。

Substantially free means free of other than inevitable impurities. In the present invention, the content of unavoidable impurities means, for example, 0.01% or less (the same applies hereinafter).

P₂O₅Is a component that reduces ion exchange performance and brittleness. Although P may not be contained₂O₅But in the presence of P₂O₅P in the case of₂O₅The content of (b) is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, P₂O₅When the content of (b) is more than 6%, the glass after chemical strengthening treatment (hereinafter also referred to as "chemically strengthened glass") has a reduced compressive stress and reduced acid resistance, and therefore P is present₂O₅The content of (b) is preferably 6% or less, more preferably 4% or less, and further preferably 3% or less. In addition, P is added to the glass so that striae are not easily generated during melting and the quality of the glass is not deteriorated₂O₅The content of (b) is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. Further, it is preferable that P is not substantially contained₂O₅。

CaO is a component for improving the meltability of the glass and also a component for improving the Young's modulus, and may contain CaO. The content of CaO in the case of containing CaO is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. On the other hand, when the content of CaO is more than 20%, the ion exchange performance is remarkably lowered, and therefore the content of CaO is preferably 20% or less. The content of CaO is more preferably 14% or less, further preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less.

SrO is a component for improving the melting property of glass and also a component for improving the young's modulus, and may contain SrO. When SrO is contained, the SrO content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. On the other hand, when the SrO content is more than 20%, the ion exchange performance is significantly reduced, and therefore the SrO content is preferably 20% or less, more preferably 14% or less, still more preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less. In order to reduce brittleness, the SrO content is preferably 3% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. Further, it is preferable that SrO is not substantially contained.

BaO is a component for improving the meltability of the glass material and also a component for improving the young's modulus, and BaO may be contained. When BaO is contained, the content of BaO is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more. On the other hand, when the content of BaO is more than 15%, the ion exchange performance is remarkably lowered, so the content of BaO is preferably 15% or less. The content of BaO is more preferably 10% or less, still more preferably 8% or less, and particularly preferably 6% or less. In order to reduce brittleness, the content of BaO is preferably 3% or less, more preferably 0.5% or less, and further preferably 0.1% or less. Further, it is preferable that BaO is not substantially contained.

ZnO is a component for improving the meltability of the glass, and may contain ZnO. When ZnO is contained, the content of ZnO is preferably 0.25% or more, and more preferably 0.5% or more. On the other hand, when the content of ZnO is more than 10%, the weatherability of the glass is remarkably lowered, so the content of ZnO is preferably 10% or less. The content of ZnO is more preferably 7% or less, still more preferably 5% or less, particularly preferably 2% or less, and most preferably 1% or less.

TiO₂Is a component for improving Young's modulus, and may contain TiO₂. In the presence of TiO₂TiO in the case of (2)₂The content of (b) is preferably 0.1% or more, more preferably 0.15% or more, and further preferably 0.2% or more. On the other hand, TiO₂When the content of (B) is more than 5%, the glass may be easily devitrified during melting and the quality of the glass may be deteriorated, so that TiO may be used₂The content of (b) is preferably 5% or less. TiO 2₂The content of (b) is preferably 3% or less, more preferably 1% or less, still more preferably 0.5% or less, and particularly preferably 0.25% or less.

ZrO₂Is a component for increasing the surface compressive stress generated by ion exchange and also for improving the Young's modulus, and may contain ZrO₂. In the presence of ZrO₂ZrO in the case of (1)₂The content of (b) is preferably 0.5% or more, more preferably 1% or more. On the other hand, ZrO₂When the content of (b) is more than 8%, the glass may be easily devitrified during melting to deteriorate the quality of the glass, and thus ZrO may be present₂The content of (b) is preferably 8% or less. ZrO (ZrO)₂The content of (b) is more preferably 6% or less, still more preferably 4% or less, particularly preferably 2% or less, and most preferably 1.2% or less.

La₂O₃、Nb₂O₅Is a component for improving Young's modulus, and may contain La₂O₃、Nb₂O₅. The content of each of these components is preferably 0.5% or more, more preferably 1% or more, still more preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. On the other hand, La₂O₃、Nb₂O₅When the content of (A) is more than 8%, the glass is likely to devitrify during melting and the quality of the chemically strengthened glass may be deteriorated, so that La is likely to occur₂O₃、Nb₂O₅The content of (b) is preferably 8% or less each. La₂O₃、Nb₂O₅The content of (b) is more preferably 6% or less, still more preferably 5% or less, particularly preferably 5% or less4% or less, and most preferably 3% or less, respectively.

In order to increase the Young's modulus, a small amount of Ta may be contained₂O₅、Gd₂O₃However, since there is a possibility that devitrification is likely to occur during melting and the quality of glass is deteriorated, the content of each of these components is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. Further, it is preferable that Ta is not substantially contained₂O₅、Gd₂O₃。

Fe₂O₃Is a component for improving the meltability of the glass. Fe₂O₃Is a component that absorbs heat rays, and therefore has the effects of promoting thermal convection of molten glass to improve the homogeneity of the glass, preventing the bottom bricks of the melting furnace from increasing in temperature to extend the life of the furnace, and the like, and in a glass melting process using a large-sized furnace, it is preferable that Fe be contained in the composition₂O₃。Fe₂O₃The content of (b) is preferably 0.002% or more, more preferably 0.006% or more, further preferably 0.01% or more, and particularly preferably 0.02% or more. On the other hand, when Fe is contained in excess₂O₃When is made of Fe₂O₃The resulting coloration becomes a problem. Fe in the oxidized state₂O₃The coloring is yellow, the coloring is blue with FeO in a reduced state, and the glass is colored green due to the balance between the two. Thus, Fe₂O₃The content of (b) is preferably 0.3% or less, more preferably 0.04% or less, still more preferably 0.03% or less, and particularly preferably 0.025% or less.

When the glass is used after being colored, a coloring component may be added within a range that does not hinder achievement of the desired reinforcing properties. The coloring component may be, for example, Co₃O₄、MnO₂、Fe₂O₃、NiO、CuO、Cr₂O₃、V₂O₅、Bi₂O₃、SeO₂、TiO₂、CeO₂、Er₂O₃、Nd₂O₃And the like as appropriate components.

The total content of these coloring components is preferably 7% or less in terms of a molar percentage based on oxides. When it is more than 7%, the glass is liable to devitrify, and thus it is not preferable. The content is preferably 5% or less, more preferably 3% or less, and further preferably 1% or less. When priority is given to the visible light transmittance of the glass, it is preferable that these components are not substantially contained.

May suitably contain SO₃Chlorides and fluorides as fining agents in glass melting. Preferably substantially no As₂O₃. In the presence of Sb₂O₃In the case of (1), Sb₂O₃The content of (B) is preferably 0.3% or less, more preferably 0.1% or less, and most preferably substantially no Sb₂O₃。

< glass characteristics >

Here, the density (. rho.) of the glass material used in the present embodiment is 2.3g/cm³～3.2g/cm³. From the viewpoint of ensuring strength and having chemical resistance such as acid resistance, the density is preferably 2.35g/cm³The above. In addition, the density is preferably 3.1g/cm for weight reduction³Hereinafter, more preferably 2.6g/cm³Hereinafter, more preferably 2.49g/cm³The following. When the density is within the above range, the bearing ball is lightweight, so that the centrifugal force at the time of high-speed rotation is not excessively generated, the force applied to a member such as a bearing can be reduced, sufficient strength can be easily secured, and damage to the glass ball and the like can be avoided.

The Young's modulus (E) of the glass material used in the present embodiment is 60GPa to 150 GPa. The Young's modulus is preferably 70GPa or more, and more preferably 80GPa or more, in order to ensure strength and wear resistance. In order to improve the acid resistance and devitrification property of the glass, the young's modulus is preferably 130GPa or less. The Young's modulus can be measured by a known method, for example, by an ultrasonic pulse method.

The glass material used in the present embodiment has an average coefficient of thermal expansion (linear expansion coefficient α) of 40 × 10 in the range of 50 to 350 ℃^-7/℃～120×10^-7V. C. The average thermal expansion coefficient is preferably 50 × 10 in consideration of the manufacturing characteristics of the glass^-7/° C or higher, more preferably 60X 10^-7Above/° c. In addition, in order to ensure dimensional accuracy, the average thermal expansion coefficient is preferably 102 × 10^-7/. degree.C.or less, more preferably 85X 10^-7Preferably 75X 10 or less/° C^-7Below/° c.

The glass ball of the present embodiment is a glass ball made of the glass material described above, and has a compressive stress layer formed on the surface thereof. When the surface has a compressive stress layer, the strength of the glass ball becomes good, and the strength can be improved to a strength suitable for use as a bearing ball. The compressive stress layer can be easily formed by tempering a glass formed in advance.

As a strengthening treatment method for forming a compressive stress layer on the surface of a glass ball, an air-cooling strengthening method, a water-cooling strengthening method (physical strengthening method), and a chemical strengthening method are known as typical methods. The air-cooling strengthening method and the water-cooling strengthening method (physical strengthening method) are methods of rapidly cooling the surface of a glass ball heated to the vicinity of the softening point by air-cooling, water-cooling, or the like. The chemical strengthening method is a method of replacing alkali metal ions having a small ion radius (typically, Li ions and Na ions) present on the surface of the glass spheres with alkali metal ions having a large ion radius (typically, Na ions or K ions for Li ions and K ions for Na ions) by ion exchange at a temperature equal to or lower than the glass transition temperature.

Since the glass spheres used in the present embodiment have a compressive stress layer on the surface thereof, glass having high mechanical strength can be obtained. In the present embodiment, any strengthening method can be employed for forming a desired compressive stress layer, but it is preferable to strengthen the glass spheres by a chemical strengthening method in order to obtain glass spheres having a small thickness and a large Compressive Stress (CS) value.

The strengthening characteristics (strengthening distribution) of chemically strengthened glass are generally expressed by Compressive Stress (CS) formed on the surface, Depth of Compressive stress (DOL), and tensile stress (CT) formed inside. Hereinafter, a case where the glass beads are chemically strengthened glass will be described as an example.

As described above, the glass sphere of the present embodiment has a compressive stress layer formed on the surface thereof. And a value of Compressive Stress (CS) at a surface of the compressive stress layer (surface of the glass ball)₀) (hereinafter, also referred to as "surface compressive stress value" or simply as "CS") is preferably 80MPa or more, more preferably 200MPa or more, still more preferably 400MPa or more, and particularly preferably 600MPa or more. Surface compressive stress value (CS)₀) When the height is increased, the mechanical strength of the glass ball is increased. Surface compressive stress value (CS), on the other hand₀) If too high, the tensile stress inside the glass may become too high, and the surface compressive stress value (CS) may become too high₀) Preferably 1500MPa or less, preferably 1300MPa or less, and more preferably 1100MPa or less.

The Depth (DOL) of the compressive stress layer formed on the surface of the glass sphere is preferably 8 μm or more, more preferably 15 μm or more, still more preferably 25 μm or more, particularly preferably 50 μm or more, and most preferably 70 μm or more. On the other hand, if DOL is too large, there is a possibility that tensile stress in the glass becomes extremely high, and therefore, the depth of layer of compressive stress (DOL) is preferably 500 μm or less, more preferably 300 μm or less, and further preferably 200 μm or less.

Surface compressive stress value (CS) of glass ball₀) And depth of compressive stress layer (DOL) by using a birefringence imaging system (manufactured by tokyo instruments, trade name: abrio), and the like. In the measurement, the glass sphere was sliced so as to include the center of the glass sphere to prepare a glass sheet having a thickness of about 0.2mm, and the retardation distribution in the glass sheet was measured.

In the above, direct measurement of the surface compressive stress value (CS) of the glass sphere is described₀) The method of (1), however, may be a method in which glass sheets having the same composition and a predetermined thickness are subjected to a strengthening treatment by the same method, and the CS of the obtained glass sheets is measured₀And DOL, thereby evaluating the characteristics of the compressive stress layer of the glass spheres.

Although the glass composition and the characteristics have been described above with respect to the glass ball of the present embodiment, it is more preferable that the glass ball for a bearing further satisfies the characteristics listed below.

The vickers hardness (Hvct) of the glass spheres of the present embodiment is preferably 6.0GPa or more, and more preferably 6.5GPa or more. In the present specification, the vickers hardness (Hvct) is the vickers hardness of the glass spheres after the strengthening treatment. Further, since measurement is difficult when the object to be measured is spherical, glass plates of the same composition having a predetermined thickness are subjected to strengthening treatment by the same method, and the vickers hardness of the obtained glass plate is measured and evaluated as the characteristic of the vickers hardness (Hvct) of the glass sphere. The Vickers hardness is measured in accordance with JIS Z2244, and the measurement is performed under the condition that the load in the Vickers hardness measurement is 100g to 200g so that the indentation length is in the range of 50 μm to 300 μm.

The diameter of the glass spheres of the present embodiment is preferably in the range of 0.5mm to 100 mm. The diameter of the bearing ball is preferably 0.5mm or more, more preferably 1.0mm or more, and still more preferably 1.5mm or more. When the diameter is too small, it is difficult to perform a strengthening treatment on the surface of the glass sphere within a range having desired characteristics, and the lower limit value is preferable from the viewpoint of this. In addition, the diameter of the bearing ball is preferably about 100mm or less, more preferably 90mm or less, and further preferably 80mm or less. In the glass spheres of the present embodiment, the higher the true sphericity is, the more preferable.

In the method for producing a glass ball according to the present embodiment, a glass sphere is produced by a conventionally known method, and a compressive stress layer is formed on the surface of the sphere by a strengthening treatment or the like, thereby obtaining the glass ball according to the present embodiment.

That is, glass spheres can be obtained by mixing raw materials of the respective components of the glass to obtain a predetermined composition satisfying the glass composition of the glass material described above, melting the mixture by heating in a glass melting furnace or the like, homogenizing the glass by a known method, and molding the homogenized mixture. For example, the glass sphere may be formed by: the molten glass is slowly cooled to form a lump of glass, and then ground and polished to form a spherical body having a desired size. Further, the glass spheres may be formed by: using a molding die or the like, molten glass is poured into the molding die and slowly cooled, molded into a green ball, and then further ground to form a spheroid.

The obtained glass sphere is subjected to a strengthening treatment on the surface thereof to form a compressive stress layer, thereby obtaining a glass sphere of the present embodiment. Examples of the strengthening treatment include the air-cooling strengthening method, the water-cooling strengthening method (physical strengthening method), and the chemical strengthening method.

Hereinafter, the chemical strengthening treatment will be specifically described. The chemical strengthening treatment can be carried out by a conventionally known method. That is, the chemical strengthening treatment can be achieved by: a spherical glass body is brought into contact with a melt containing a metal salt (for example, potassium nitrate) of a metal ion (typically, a K ion) having a large ionic radius by dipping or the like, thereby replacing the metal ion (typically, a Na ion or a Li ion) having a small ionic radius in the glass with the metal ion having a large ionic radius.

The chemical strengthening treatment (ion exchange treatment) is not particularly limited, and may be carried out, for example, by: the spherical glass body is immersed in a molten salt such as potassium nitrate heated to 360 to 600 ℃ for 0.1 to 500 hours. The heating temperature of the molten salt is preferably 375 to 500 ℃, and the time for immersing the glass plate in the molten salt is preferably 0.3 to 200 hours.

Examples of the molten salt used for the chemical strengthening treatment include: nitrates, sulfates, carbonates, chlorides, and the like. Among them, as the nitrate, there can be mentioned: lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate, and the like. As the sulfate, there may be mentioned: lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate, and the like. As the carbonate, there may be mentioned: lithium carbonate, sodium carbonate, potassium carbonate, and the like. As the chloride, there may be mentioned: lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, and the like. These molten salts may be used alone or in combination of two or more.

In the present embodiment, the processing conditions for the chemical strengthening treatment are not particularly limited, and appropriate conditions may be selected in consideration of the characteristics and composition of the glass, the type of molten salt, and the desired chemical strengthening properties such as the surface Compressive Stress (CS) and the depth of compressive stress layer (DOL) required for the finally obtained glass spheres.

In the present embodiment, the chemical strengthening treatment may be performed only once, or may be performed a plurality of times under two or more different conditions (multi-step strengthening). Here, for example, when the chemical strengthening treatment is performed as the chemical strengthening treatment of the first step under the condition that the CS becomes relatively low, and then the chemical strengthening treatment is performed as the chemical strengthening treatment of the second step under the condition that the CS becomes relatively high, the internal tensile stress area (St) can be suppressed while the CS of the outermost surface of the chemically strengthened glass is increased, and as a result, the internal tensile stress (CT) can be suppressed to be low.

(second embodiment)

Next, a glass ball of a second embodiment will be described. The glass beads described here contain Li as a material having more preferable glass composition and glass characteristics, which is used for the glass beads of the first embodiment₂And O-containing Li glass as a glass material. The following description is made in detail.

Examples of the Li-containing glass used herein include the following: the glass contains, expressed in mole percent on an oxide basis: 50 to 75 percent of SiO₂4 to 20 percent of Al₂O₃1 to 15% of Li₂O, 5 to 25 percent of R₂O (wherein R is at least one selected from Li, Na and K), 0-15% MgO, and SiO₂+Al₂O₃+R₂The content of O + MgO is more than 92%.

In the present embodiment, SiO₂The content of (b) is preferably 50% or more. SiO 2₂The content of (b) is more preferably 55% or more, still more preferably 60% or more, and particularly preferably 65% or more. On the other hand, SiO₂The content of (B) is preferably 75%Hereinafter, more preferably 68% or less.

Al₂O₃The content of (b) is preferably 4% or more. Al (Al)₂O₃The content of (b) is more preferably 5% or more, still more preferably 6% or more, and particularly preferably 7% or more. On the other hand, Al₂O₃The content of (b) is preferably 20% or less, more preferably 15% or less, still more preferably 12% or less, and particularly preferably 10% or less.

When the chemical strengthening treatment is performed by replacing Li ions on the glass surface with Na ions, Li is present₂The content of O is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, particularly preferably 5% or more, and most preferably 7% or more. On the other hand, Li₂The content of O is preferably 15% or less, more preferably 12% or less, and further preferably 10% or less.

R₂The content of O (where R is one or more selected from Li, Na, and K) is 5% or more, preferably 8% or more, more preferably 10% or more, and still more preferably 12% or more. In another aspect, R₂The content of O is preferably 25% or less, more preferably 20% or less, and further preferably 18% or less.

The content of MgO is 0 to 15%, preferably 0.1% or more, more preferably 1% or more, further preferably 3% or more, and particularly preferably 5% or more. On the other hand, the content of MgO is preferably 15% or less, more preferably 14% or less, further preferably 11% or less, and particularly preferably 9% or less.

In the Li-containing glass of the present embodiment, in order to increase the young's modulus while keeping the density low and to achieve sufficient strength and abrasion resistance, the total of the above components (SiO) is preferably used₂+Al₂O₃+R₂O + MgO) is set to 92% or more. The total amount of these components is more preferably 95% or more, and still more preferably 97% or more.

In addition, optional components may be contained in the same manner as in the first embodiment.

In the Li-containing glass of the present embodiment, the wear resistance is maintained and the Li-containing glass is easily hardenedFrom the viewpoint of preventing the deterioration of glass quality due to devitrification during melting, ZrO and TiO₂Total amount of (ZrO + TiO)₂) Preferably 0 to 2%. The total amount of (ZrO + TiO)₂) Preferably 0.1% or more, more preferably 0.15% or more, and still more preferably 0.2% or more. In addition, the total amount of (ZrO + TiO)₂) More preferably 1.5% or less, and still more preferably 1% or less.

The Li-containing glass having the above composition is a glass material having a low density, a high strength and a high young's modulus, and is particularly preferably used for a lightweight, high-strength glass bearing ball. The Li-containing glass tends to have glass characteristics within the ranges described below.

The density of the Li-containing glass is preferably 2.3g/cm³～2.5g/cm³. The density is more preferably 2.35g/cm³Above, more preferably 2.42g/cm³The density is more preferably 2.47g/cm³Hereinafter, more preferably 2.45g/cm³The following.

The Young's modulus of the Li-containing glass is preferably 75GPa to 95 GPa. The Young's modulus is more preferably 80GPa or more, and the Young's modulus is more preferably 90GPa or less.

The average coefficient of thermal expansion (coefficient of linear expansion α) of the Li-containing glass in the range of 50 ℃ to 350 ℃ is preferably 50X 10^-7/℃～90×10^-7V. C. The average coefficient of thermal expansion is more preferably 60X 10^-7/. degree.C.or higher, more preferably 70X 10^-7Above/° c. Further, the average thermal expansion coefficient is more preferably 85 × 10^-7Preferably 75X 10 or less/° C^-7Below/° c.

Surface compressive stress value (CS) of Li-containing glass₀) Preferably 80MPa or more, more preferably 120MPa or more. The surface compressive stress value is preferably 1500MPa or less, more preferably 1300MPa or less. The Li-containing glass is easy to further improve the surface compressive stress value (CS) by strengthening treatment₀) Surface compressive stress value (CS) after strengthening treatment₀) Preferably 400MPa or more, more preferably 600MPa or more. The surface compressive stress value after the strengthening treatment is preferably 1100MPa or less, and more preferably 900MPa or less.

(third embodiment)

Next, a glass ball according to a third embodiment will be described. The glass beads described here contain Y as a material having more preferable glass composition and glass characteristics, which is used for the glass beads of the first embodiment₂O₃Containing Y of₂O₃Glass beads obtained by using glass as a glass material.

The following description is made in detail.

As used herein, Y-containing₂O₃Examples of the glass include the following: the glass contains, expressed in mole percent on an oxide basis: 30 to 70 percent of SiO₂4 to 30 percent of Al₂O₃5 to 20 percent of Li₂O, 5 to 25 mol% of R₂O (wherein, R is more than one selected from Li, Na and K), 1 to 25 percent of MgO and 1 to 20 percent of Y₂O₃。

In the present embodiment, SiO₂The content of (b) is preferably 30% or more. SiO 2₂The content of (b) is more preferably 35% or more, and still more preferably 38% or more. On the other hand, SiO₂The content of (b) is preferably 70% or less, more preferably 65% or less.

Al₂O₃The content of (b) is preferably 4% or more. Al (Al)₂O₃The content of (b) is more preferably 5% or more, still more preferably 10% or more, and particularly preferably 15% or more. On the other hand, Al₂O₃The content of (b) is preferably 30% or less, more preferably 27% or less.

When the chemical strengthening treatment is performed by replacing Li ions on the glass surface with Na ions, Li is present₂The content of O is preferably 5% or more, more preferably 7% or more. On the other hand, Li₂The content of O is preferably 20% or less, more preferably 17% or less.

R₂The content of O (where R is one or more selected from Li, Na, and K) is 5% or more, preferably 8% or more, more preferably 10% or more, and still more preferably 12% or more. In another aspect, R₂The content of O is preferablyIs 25% or less, more preferably 20% or less, and still more preferably 18% or less.

The content of MgO is 1% to 25%, preferably 2% or more, and more preferably 3% or more. On the other hand, the content of MgO is preferably 20% or less, more preferably 17% or less, and further preferably 15% or less.

Y₂O₃Is a component for improving the Young's modulus without making the density too large, thereby improving the abrasion resistance. Y is₂O₃The content of (b) is 1% to 20%, preferably 2% or more, and more preferably 3% or more. On the other hand, Y₂O₃When the content of (b) is more than 20%, the acid resistance of the glass is lowered or the devitrification temperature is increased. Y is₂O₃The content of (b) is preferably 20% or less, more preferably 11% or less, and further preferably 9% or less.

In addition, optional components may be contained in the same manner as in the first embodiment.

In the present embodiment, Y is contained₂O₃In the glass, from the viewpoint of maintaining abrasion resistance and preventing deterioration of glass quality due to devitrification at the time of melting, the above-mentioned ZrO and TiO₂Total amount of (ZrO + TiO)₂) Preferably 0 to 2%. The total amount of (ZrO + TiO)₂) Preferably 0.1% or more, more preferably 0.15% or more, and still more preferably 0.2% or more. In addition, the total amount of (ZrO + TiO)₂) More preferably 1.5% or less, and still more preferably 1% or less.

Of the above composition containing Y₂O₃Glass is a high-strength and high-hardness glass material, is particularly preferably used for a high-durability and high-strength glass bearing ball, and is excellent in abrasion resistance. The compound containing Y₂O₃The glass preferably has glass characteristics within the ranges described below.

Containing Y₂O₃The density (. rho.) of the glass is preferably 2.3g/cm³～3.2g/cm³. The density is more preferably 2.6g/cm³Above, more preferably 2.8g/cm³The density is more preferably 3.1g/cm³The following.

Containing Y₂O₃The Young's modulus of the glass is preferably 80GPa to 150 GPa. The Young's modulus is more preferably 90GPa or more, and is more preferably 130GPa or less, still more preferably 125GPa or less, and particularly preferably 120GPa or less.

Containing Y₂O₃The average coefficient of thermal expansion (coefficient of linear expansion α) of the glass in the range of 50 ℃ to 350 ℃ is preferably 40X 10^-7/℃～90×10^-7V. C. The average coefficient of thermal expansion is more preferably 50X 10^-7/. degree.C.or higher, more preferably 55X 10^-7The average coefficient of thermal expansion is more preferably 85X 10℃ or more^-7Preferably 80X 10 or less/° C^-7Below/° c.

Containing Y₂O₃The Vickers hardness (Hv) of the glass is preferably 6.0GPa or more, and more preferably 6.5GPa or more. The compound containing Y₂O₃The glass is easily subjected to strengthening treatment to further increase vickers hardness, and vickers hardness (Hvct) after the strengthening treatment is preferably 7.0GPa or more, and more preferably 7.5GPa or more.