JPH02129056A - Production of spherical ceramics - Google Patents

Abstract

PURPOSE:To increase the roundness of ceramic balls by calcinating ceramic powder products formed into an around sphere with a little roughness on its surface, treating the product with dry ball mill, sintering and conducting surface treatment. CONSTITUTION:A ceramic powder 2 containing a sintering auxiliary is charged into a molding press 1, pressed in the arrow direction to give a spherical ceramic ball 3 with a little roughness on its surface. The pressed product 3 is calcined in a nitrogen atmosphere, dry-treated with a ball-mill to give the balls 4. The balls 4 are sintered and surface-treated by barrel finishing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing ceramic spheres.

[Prior Art] So-called fine ceramics such as silicon nitride and silicon carbide have excellent corrosion resistance and wear resistance, and are used in various fields as structural materials and parts. Ceramic bearings are one such application, and many proposals have been made because they are lighter than metals and can be used in corrosive environments and high temperatures.

For example, in JP-A No. 63-57204, a cylindrical body made of a powder compact (ceramic powder compact) having a height almost equal to the diameter is prepared, the cylindrical body is chamfered, and then fired. A method of manufacturing spheres is disclosed that involves binding and then surface treatment.

[Problems to be Solved by the Invention] However, the method described in JP-A No. 63-57204 involves chamfering a powder compact such as ceramic, sintering it, and performing surface processing such as barrel polishing.
The amount removed is small, about 0.1+m+m or several mm, and the unevenness from the chamfering process remains.As a result, the roundness of the sphere obtained as a final product is low.For example, the diameter is 10.
The diameter of the sphere is 0.5 to 1 mn+. Therefore, the ceramic spheres obtained by the above method do not have sufficient performance as, for example, a bearing.

As described above, in the prior art, there is no known method for easily obtaining ceramic spheres with excellent performance.

The present invention is intended to solve the above problems in the prior art, and its purpose is to provide a method for manufacturing ceramic spheres that is simple and has a wide range of applications.

[Means for Solving the Problems 1] That is, the method for producing a ceramic sphere of the present invention involves producing a substantially spherical ceramic powder molded body having slight irregularities on the surface by press molding, then calcining the molded body, and then calcining the molded body. It is made into a sphere by dry ball milling, then sintered,
It is further characterized by surface treatment.

Ceramics that can be used in the method of the present invention include one of oxides, carbides, nitrides, borides, or combinations thereof.
It may be one that is commonly used.

The size and shape of the approximately spherical ceramic powder molded body with some irregularities on the surface, which is produced by press molding the above ceramic, are not particularly limited, and are selected in consideration of the application and moldability. The closer to a spherical shape, the less the need for grinding or polishing later, so it is best to choose a shape that is balanced with ease of press molding.

Calcining temperature of ceramic powder compact, calcination time, grinding time by dry ball mill, number of processed pieces, size of ball mill container, rotation speed, sintering temperature, sintering time, surface processing means and time, etc. The conditions depend on various factors such as the type of ceramic, the size and shape of the ceramic powder compact, the size and roundness of the sphere obtained by dry ball milling, the size and roundness of the desired ceramic sphere, and workability. and select the best one.

The means of surface treatment may be conventional means, such as barrel polishing.

[Function 1] When a ceramic powder molded body produced by press forming is calcined and then subjected to dry ball mill treatment, the unevenness on the surface of the ceramic powder molded body can be preferentially removed, so that the roundness can be improved to a considerable extent without using any special processing tools. A tall sphere can be obtained. Therefore, surface processing after sintering is facilitated, and roundness after surface processing is improved.

[Example 1] The present invention will be explained in further detail in the following examples and comparative examples. Note that the present invention is not limited to the following examples.

3.0 g of 5isN<powder 2 (average particle size 0.9 μm) containing 5% by weight of Y2O3 and 5% by weight of 8β20° as sintering aids was put into the forming press 1 shown in FIG. Apply pressure in the direction of the arrow at a pressure of 1000 Kg/cm' to a diameter of 1
A molded body 3 having a shape shown in FIG. 2 and having a diameter of 5 mm and a height of 15++v+ was obtained.The molded body 3 was then calcined at 1300° C. for 2 hours in a N atmosphere. This calcined body was placed in a ball mill pot (outer diameter 40 cm, inner diameter 30 cm, height 40 cm) for 500 min.
The pieces were placed in individual pieces and rotated dry at 5 Orpm for 36 hours. During this time, the calcined bodies came into contact with each other and the uneven parts were scraped off, yielding a sphere 4 with a diameter of just over 12 mm. 6 Next, the sphere 4 was sintered in N atmosphere at 1750°C for 2 hours, and then barrel-polished for 15 hours. A sphere 5 of 10 mm was obtained. When the roundness of the sphere 5 was measured, it was 0. O was 5 nm.

(Comparative Example) The same method as described in JP-A No. 63-57204 was used. 2.5 g of the same 5isN4 powder 2 as in the example was put into the molding press 6 shown in Fig. 3, and pressed in the direction of the arrow in the figure with a pressure of 1000 Kg/cm' to form a diameter of 12 m.
A cylindrical molded body 7 as shown in FIG. 4 with a height of 12+nm (a = 12 mm) was obtained. Next, the molded body 7 was chamfered using a lathe as shown in FIG. 5, so that both ends became truncated cones. The diagonal length a of the (truncated conical) shaped molded body 8 after chamfering was approximately 12 mm. Next, after degreasing the molded body 8,
Sintering was performed at 1750° C. for 4 hours in a N2 atmosphere, and barrel polishing was performed for 15 hours to obtain a sphere 9 with a diameter of 10 mm.The roundness of the sphere 9 was measured to be 0.5 mm.

From the results of the above Examples and Comparative Examples, it can be seen that the ceramic spheres obtained by the method of the present invention have much better roundness than the ceramic spheres obtained by the conventional method.

[Effect of the invention 1 As described above, the method for producing ceramic spheres of the present invention further performs surface processing after ball milling the calcined ceramic powder compact, so unlike the conventional method, the method for producing ceramic spheres is Since processing tools such as lathes are not required, and spheres with a high degree of roundness can be obtained through ball milling, ceramic spheres with very good roundness can be easily produced through subsequent surface processing such as barrel polishing. Obtainable.

Therefore, the method of the present invention has a simpler manufacturing process than conventional methods, is suitable for mass production, and can be applied to a wide range of applications as it can similarly manufacture ceramic spheres of various materials and sizes.

Furthermore, since the ceramic spheres obtained by the method of the present invention have extremely high roundness, the reliability and durability of various devices using the ceramic spheres are greatly improved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the process of manufacturing a ceramic powder molded body in one embodiment of the method for manufacturing ceramic spheres of the present invention, and Figure 2 shows the processing order of the ceramic powder molded body obtained in the process of Figure 1. FIG. 3 is an explanatory diagram of the process of manufacturing a ceramic powder molded body as an example of a conventional ceramic sphere manufacturing method. FIG. 4 is a processing order of the ceramic powder molded body obtained in the process of FIG. 3. FIG. 5 is an explanatory diagram of the chamfering process in FIG. 4. In the figure, 1.6... Molding press 2...5 is N4 powder 3
．． 7.8... Molded object 4,5.9... Sphere (2 idiots) Figure 1, Section 2! Figure 3: Cloudy Figure 4: Sphere 9 Figure 5

Claims (1)

[Claims] A nearly spherical ceramic powder molded body with slight irregularities on the surface is produced by press molding, then the molded body is calcined and then formed into a sphere by dry ball milling, then sintered, and further surface processed. A method for producing characteristic ceramic spheres.