KR100795339B1 - Fabrication of ceramic ball and alumina ceramic bearing - Google Patents

Abstract

A method of fabricating a ceramic ball using a mold, a surface reinforced ball, and housing and an alumina ceramic bearing by the same is provided to improve durability of ceramic ball bearing and to present a centrifugal molding method in manufacturing the alumina bearing ball. A method of fabricating a ceramic includes the steps of: remove large pieces or lumps of ceramic slurry after rotating alumina ceramic slurry in a mold at high speed(S100); producing an alumina ceramic ball molding body through high speed centrifugal molding(S200); reinforcing the surface of the produced alumina ceramic ball through coating with glass powder and heating after high temperature sintering and rough processing(S300); and performing fine processing and washing of the surface reinforced ceramic ball(S400).

Description

Ceramic ball manufacturing method and alumina ceramic ball bearing using the same {Fabrication of Ceramic ball and alumina ceramic bearing}

1 is a process diagram briefly showing only essential steps of the alumina ceramic ball manufacturing method according to the present invention,

Figure 2 is a plan view showing a mold for a bearing ball according to an embodiment of the present invention,

3 is a cross-sectional view taken along line AA of FIG.

Figure 4 is a side view showing the mounting bracket to the bearing ball mold.

<Description of Symbols for Major Parts of Drawings>

10: housing 40: fixing means

50: hollow 60: ball forming mold

60a: sphere 60b: inlet pipe

80: supply

The present invention relates to a method for manufacturing a ball bearing with a mold for producing a ceramic ball and a surface-reinforced ball and a housing, and more particularly, a method for manufacturing a ceramic ball and a housing by centrifugal molding and a method for manufacturing an alumina ceramic ball bearing using the same. It is about.

Ceramic materials have low density, low thermal expansion rate, high hardness and heat resistance, and they are applied to various mechanical parts. Especially, ceramics, which are bearing materials that can be used in harsh conditions with the rapid development of the machinery industry, have excellent high temperature stability and corrosion resistance. In addition, it is widely applied due to its superior stiffness and fatigue resistance than steel.

Currently, corrosion resistant bearings used in acid, alkali, etc. are mostly ZrO ₂ and Si ₃ N ₄ , and Si ₃ N _{4 and} Al ₂ O ₃ are used mainly for high-temperature and high-speed bearings. ZrO ₂ used in general corrosion resistant bearings has three types of crystal structure phase transformation (single crystal → tetragonal crystal → cubic crystal) as the sintering temperature rises. Happens. At this time, it is difficult to sinter alone with condensed milk, which causes the specimen to be broken due to volume expansion of about 4%.

Therefore, in order to improve sinterability, ZrO ₂ is used by adding one kind selected from among Y ₂ O ₃ , CeO ₂ , and MgO as a stabilizer. Where Y ₂ O ₃ is added to ZrO ₂ , its mechanical properties are excellent, but its corrosion resistance is mainly applied to general wear-resistant products such as cutters, and when CeO ₂ or MgO is added, Due to excessive grain growth, the mechanical properties are insufficient. On the other hand, Al ₂ O ₃ is an economical material having excellent hardness and corrosion resistance, but has a problem that strength and wear resistance are difficult to apply to bearings as compared to other ceramic materials Si ₃ N ₄ and ZrO ₂ .

Accordingly, the present invention has been made to solve the above problems, an object of the present invention is to provide a method for manufacturing alumina ceramic ball bearings, which has improved durability by strengthening the surface of the alumina ceramic ball and the housing.

Another object of the present invention is to provide a ceramic ball molding method by centrifugal molding and a mold for manufacturing the same in manufacturing the alumina ceramic ball bearing.

The object of the present invention as described above is a constant in the periphery of the supply portion and the supply portion is formed by extending the circumference of the predetermined length in the up and down direction from the hollow housing and the inner peripheral vertical center of the housing, respectively, the upper and lower portions are separated It is achieved by a mold for producing a bearing ball comprising a ball forming frame consisting of a plurality of inlet pipes and a spherical frame extending outwardly at equal intervals and fastening means for fastening the upper and lower portions of the housing. Here, the housing is preferably composed of a transparent body so that the interior is reflected.

In addition, an object of the present invention is a method for producing alumina ceramic ball,

Centrifuging the ceramic slurry to remove large particles or agglomerates, and then rotating the ceramic slurry at a high speed to complete the ceramic molded body;

After sintering the ceramic formed body produced through the above steps, applying glass powder to the surface of the sintered body and heat-treating it to strengthen the surface;

Precision machining and cleaning the surface of the ceramic sintered body;

It can also be achieved by a method for producing alumina ceramic ball comprising a.

On the other hand, the present invention is a method for producing alumina ceramic ball, the mold is hollow, the housing configured to be separated from each other from the vertical vertical center of the hollow and the inner peripheral vertical center of the housing at regular equal intervals outward It is characterized in that it consists of a ball forming frame consisting of a plurality of elongated inlet pipes and spherical frame and the fixing means for fixing the upper and lower parts of the main body.

These and other objects, advantages and features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings of preferred embodiments.

Hereinafter, with reference to the drawings showing a preferred embodiment of the present invention will be described in detail, but before, the related art used in the present invention will be briefly described.

Related technologies used in the present invention are the registered patents No. 314100 and No. 555222 owned by the applicant of the present invention. This relates to "Ceramic Tube Manufacturing Method and Fabricated Ceramic Tube by Centrifugal Molding" and "Surface Modification Method and Surface-Modified Oxide Ceramics of Oxide Ceramics Using Glass". The former is a high quality ceramic tube manufacturing technology. The latter technique is to improve the strength, thermal shock resistance and wear resistance of ceramics.

1 is a process diagram schematically showing an essential process of the alumina ceramic ball manufacturing method according to the invention, Figure 2 is a plan view showing a mold for a bearing ball, Figure 3 is a cross-sectional view AA of Figure 2, Figure 4 is a mold for a bearing ball Side view showing the mounting brackets on both sides of the

The configuration of the bearing ball manufacturing mold according to the present invention is largely the housing 10, the inlet pipe (60b) and the ball mold 60 formed integrally with the spherical frame (60a), the upper and lower parts of the housing (10) It consists of a fixing means 40 for fixing the coupling.

The housing 40 has a hollow 50 shape, and a ball molding in which the inlet pipe 60b and the spherical frame 60a are integrally formed around the vertical center of the hollow 50 in the outward direction of the housing 40. The mold 60 is provided. In addition, the ball molding frame 60 is provided in plural at regular intervals around the vertical center of the hollow 50.

The housing 40 may be made of a two-component epoxy resin, an unsaturated polyester resin, or a transparent acrylic plate so that the housing 40 may be visually observed from the outside.

Fixing means 40 is configured to fix the housing 10 is separated from the vertical center of the hollow 50 up and down. The fixing means 40 may be a conventional wrench bolt, and various selections may be made by those skilled in the art such as Sams Bolt, Square Neck Bolt, and the like.

The spherical mold 60a is provided for drying the slurry introduced from the inlet pipe 60b for a predetermined time to produce the slurry in the shape of a sphere. In the present invention, although the spherical degree is subjected to a series of processes to produce a precision ball (G10 class) of 1 micron or less, the spherical mold 60a is also preferably manufactured precisely.

The inlet pipe 60b is configured to allow the slurry to flow into the spherical mold 60a, which is also smaller than the diameter of the spherical mold 60a for precise precision, and the diameter of the slurry can be sufficiently introduced. do.

Hereinafter, a method of manufacturing an alumina ceramic ball bearing using a mold for manufacturing a bearing ball will be disclosed, but will be limited to only the characteristic parts of the present invention during a conventional ball bearing manufacturing process.

The manufacturing method of the alumina ceramic ball bearing using the bearing ball manufacture mold of this invention is as follows.

Centrifuging the alumina ceramic slurry to remove large particles or agglomerates, and then placing them in a mold, rotating them at high speed, and then removing them when the large particles or agglomerates are formed again (S100);

The step (S200) of manufacturing the alumina ceramic ball molded body by high-speed centrifugal molding by putting the slurry from which the large particle mass is removed through the step (S100) in the mold;

High temperature sintering of the alumina ceramic ball molded body produced by the step (S200) and then the glass powder is applied to the surface through the roughing step and the surface heat treatment to strengthen the surface (S300) and

It comprises a step (S400) of precisely processing and washing the surface of the alumina ceramic ball molded body after the step (S300) to the final dimensions.

The alumina ceramic slurry of step (S100) is a dispersion of the ceramic powder in a liquid solvent and a salt is added to the solid content of about 5 to 25% by volume and very weakly agglomerated ceramic particles. The ceramic powder is alumina, zirconia, mixtures thereof, and the like, and the mixing ratio of the liquid solvent and the ceramic powder is such that the solids content of the slurry is about 5 to 25% by volume. Preferably, the solids content of the slurry is 5% to 20% by volume. In addition, a binder may be added to the ceramic slurry to increase the strength of the molded body. Many binders used in ceramic molding are known and are broadly classified into clay binders, molecular binders and film-forming binders. Molecular binders and film-forming binders are used in the manufacture of high purity ceramics. Molecular binders are further divided into vinyl binders, cellulose binders, and polyethylene glycol binders. The binder used in the present invention is not particularly limited and a vinyl binder may be used. The binder used in the embodiment of the present invention is a product diluted so that the ratio of PVA (polyvinyl alcohol) to water is 20% by weight. The amount of the binder (solid PVA) is 1 wt% or less with respect to the ceramic powder, preferably 0.8 wt% or less.

The reason for the salt addition is to very weakly aggregate the ceramic powder particles in the slurry. When the ceramic powder in the slurry is very weakly aggregated, the forming speed is faster than that of the fully dispersed slurry, and the structure of the molded body is uniform. Salt used for this purpose is a water-soluble electrolyte, i.e. Li ^+, Na ^+, K ^+, Rb ^+, NH ₄ ^+, Mg ₂ ^+, Ca ₂ ^+, Sr ₂ ^+, Ba ₂ ⁺ ions and SO ₄ ^{2 -,} C1 ^- , NO ₃ ^- ions and the like. Examples include NH ₄ Cl and the like. The addition concentration of the salt may vary depending on the type of salt, because the greater the valence of the electrolyte ions, the greater the ability to aggregate, but is generally 0.5 M or less, preferably 0.1 M to 0.3 M with respect to the liquid solvent.

In addition, additives commonly used in the art, for example, antifoaming agents, plasticizers and the like can be added.

On the other hand, this very weakly agglomerated slurry is poured into a cylindrical mold, plugged and centrifuged to sediment large particles and agglomerates using centrifugal force. At this time, the strength or duration of the appropriate centrifugal force field depends on the size of the mold, the particle size of the ceramic powder, and the like, and can be determined by a person of ordinary skill in the art by a few experiments. After the centrifugal sedimentation, the stopper of the mold is opened to recover the slurry collected in the center. This slurry is a slurry from which large particle masses, impurities, etc., which may cause non-uniformity of microstructures are removed.

The slurry from which such large particles are removed is poured into a cylindrical mold with one end cap and the other end with a cap and then centrifuged by centrifugal force. After the centrifugal molding, one stopper of the mold is opened, the liquid solvent collected in the center is poured out, and the desired molded body is obtained by drying.

Here, the mold to be used may be a cylindrical mold for producing the inner and outer rings of the bearing or the bearing ball as described above, and a mold for producing the bearing ball as described above. And such a mold is not an alternative choice, but the cylindrical mold is to create a molded body for manufacturing the inner and outer rings of the bearing, the bearing ball mold is to create a ball provided in the bearing, so the two molds By using it, the molded object for inner and outer rings, and a ball molded object are manufactured.

In addition, the bearing ball mold is coupled to each of the housings 10 divided into upper and lower parts, and the centrifugal force is rotated by a rotational shaft (not shown) passing through the center of the fixing unit 30 and the housing 10. It is molding. Therefore, in order to produce the ball with the bearing ball mold, the slurry containing the weakly aggregated in the supply unit 80 provided inside the housing 10 is rotated at a high speed. The slurry is moved to the spherical mold 60a through the inlet pipe 60b by the rotation of the high speed, and the slurry aggregates in the spherical mold 60a.

Whether the slurry is evenly aggregated in the spherical mold 60a is possible by the housing 10 made of a transparent material.

The inner and outer ring molded body and the ceramic ball molded body formed by such a process are subjected to a step of sintering. In the case of the ceramic ball molded body, roughing is performed after sintering to improve sphericity.

In addition, ceramics are known to have high melting points, and in particular, alumina is melted at 2046 ° C. Therefore, although glass differs depending on a composition, when temperature is 1000 degreeC or more, glass will melt | dissolve and become a liquid, and can penetrate into the surface layer of an alumina ceramic sintered compact (sintered body for inner and outer rings, ball sintered compact).

As the cracks of the alumina ceramic molded body are filled and healed by the impregnated glass, the strength is improved. Particularly, compressive stress is generated in the surface layer of the alumina ceramic molded body during cooling to room temperature when using a glass having a low coefficient of thermal expansion compared to the alumina ceramic as the base material. In addition, the compressive stress improves strength, thermal shock resistance, and wear resistance.

Among the alumina ceramic sintered bodies completed by such high temperature sintering and surface treatment, in particular, the ball sintered body improves sphericity through precision surface smoothing. The surface of the alumina ceramic molded body is washed to complete the ball molded body for bearing and the sintered body for inner and outer rings.

The alumina ceramic bearing is completed by assembling the bearing by a conventional bearing assembly method using the completed ball sintered body for bearings and the sintered body for inner and outer rings.

According to the alumina ceramic ball manufacturing method using the bearing ball manufacturing mold according to the present invention as described above, it is possible to manufacture the spherical shaped body in an economical manner, and there is an effect that can significantly reduce the processing cost.

In addition, the surface of the ceramic ball and the inner and outer rings are strengthened by the surface modification method, so that the surface state is good and the wear resistance is improved, thereby enabling high speed rotation.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be readily apparent to those skilled in the art that various other modifications and variations are possible without departing from the spirit and scope of the present invention. It is obvious that all belong to the appended claims.

Claims (7)

A housing 10 of the hollow 50 in which the upper and lower portions are separated; A slurry supply unit 80 configured to extend outwardly a circumference of a predetermined length in the vertical direction from an inner circumferential vertical center of the housing 10; A ball molding frame (60) consisting of a plurality of inlet tubes (60b) and a spherical frame (60a) extending outwardly at regular equal intervals around the supply part (80); Fixing means (40) for coupling and fixing the upper and lower portions of the housing (10); Bearing ball manufacturing mold, characterized in that comprising a. The method of claim 1, The housing 10 is a mold for manufacturing a bearing ball, characterized in that configured as a transparent body so that the inside is reflected. The method of claim 1, The ball molding frame 60 is a mold for producing a bearing ball, characterized in that arranged radially from the vertical center of the housing (10). In the alumina ceramic ball manufacturing method, Centrifuging the alumina ceramic slurry to remove large particles or agglomerates, and then placing them in a mold and rotating them at high speed, and then removing the large particles or agglomerates (S100); A step (S200) of manufacturing the alumina ceramic ball molded body by high-speed centrifugation by putting the slurry from which the large particle mass is removed through the step (S100) in the mold; Sintering the alumina ceramic ball molded body produced through the step (S200) at high temperature, and then applying a glass powder to the surface through a roughing step and performing a surface heat treatment to strengthen the surface (S300); Precisely processing and washing the surface of the alumina ceramic ball molded body which has been subjected to the step (S300) (S400); Alumina ceramic ball manufacturing method comprising a. The method of claim 4, wherein the mold, A housing 10 of the hollow 50 in which the upper and lower portions are separated; A slurry supply unit 80 configured to extend outwardly a circumference of a predetermined length in the vertical direction from an inner circumferential vertical center of the housing 10; Consists of a plurality of inlet pipes (60b) and a spherical frame (60a) extending outwardly at constant equal intervals around the supply portion 80, a plurality of ball molding frame (60) arranged radially from the vertical center of the housing (10) ); Fixing means (40) for coupling and fixing the upper and lower portions of the housing (10); Alumina ceramic ball manufacturing method comprising a. An alumina ceramic ball prepared by the method of claim 4 or 5. An alumina ceramic ball bearing manufactured using the alumina ceramic ball of claim 6.

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