JPH0248031A - Manufacture of ceramics sphere - Google Patents

Abstract

PURPOSE:To carry out inexpensive mass production by providing a rolling stage for rolling a bar-shaped body and forming continuous spheres, a sphere- separating stage, and degreasing and sintering stages. CONSTITUTION:A round bar 1 held between supporting plated 13 is inserted into an inlet between rollers 11, 12 in the direction of N. The round bar 1 is continuously deformed into a gradually reduced cross section and comes out through an outlet between the rollers 11, 12 in the form of continuous spheres 3... in which the spheres 3... are connected to each other by means of short bridges 16.... A binder contained in the above formed bodies 3 is volatiled and decomposed by heating in a degreasing furnace. Further, continuous spheres 4 after degreasing are sintered in a sintering furnace at 1650 deg.C. Moreover, the continuous spheres 4 after sintering are struck by means of a hammer, etc., by which respective spheres 3... are separated, while bounded by the parts of respective bridges 16.... By this method, material yield can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a ceramic sphere manufacturing method suitable for manufacturing fine ceramic spheres.

(Prior Art) Recently, ball bearings made of fine ceramics have been mass-produced, focusing on the wear resistance of fine ceramic molded products. The spheres used in this ball bearing are made by molding fine ceramic powder into coarse spheres, and
After sintering, the sintered rough spheres are precisely polished until they become true spheres.

Methods for producing coarse spheres include a press method in which powder is compression molded in a mold in a uniaxial direction, a rubber press method in which the powder is filled into a molded rubber shape and pressure molded using hydrostatic pressure, and a ceramic powder method. There is an injection molding method in which a thermoplastic resin is added together with a molding aid, and the heated and kneaded base material is press-fitted into a mold through a nozzle and assimilated.

However, each of these three methods used for producing coarse balls has the following drawbacks. That is,
In the press method, by uniaxially forming a spherical object,
The degree of filling of powder in the mold becomes uneven. As a result, during sintering, shrinkage rates differ locally, resulting in deformation. On the other hand, the rubber press method applies hydrostatic pressure and eliminates the density difference between the powders, but has the disadvantage that it takes time from charging the powder into the molded rubber mold to removing the molded product, making it unsuitable for mass production. Furthermore, the injection molding method has the drawback that since the molded product contains a large amount of resin, it is necessary to completely remove the resin at a slow heating rate during firing, and this degreasing process takes a long time.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing ceramic spheres that can manufacture ceramic spheres in large quantities at low cost.

[Structure of the invention]

(Means and effects for solving the problem) By rolling a rod-shaped body made of a mixture of ceramic powder and a binder, a sphere or a continuous sphere consisting of a row of spheres is obtained, and the sphere is degreased and fired. Furthermore, since the continuous sphere is separated into individual spheres, it is possible to manufacture the sphere with high accuracy and high efficiency.

(Example) Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The ceramic sphere manufacturing method of this embodiment includes a round bar forming step (see Fig. 1) in which a ceramic powder such as silicon nitride (SisN4) and a binder are mixed together and a round bar is formed using an extrusion molding machine. The round bar (1) obtained in this round bar forming process is rolled on a rolling machine as shown in Figures 2 and 3.
2) to form a continuous sphere (4) (see Fig. 4) in which the spheres (3)... are connected in a row in a skewer shape, and the product obtained in this rolling process. a degreasing process of degreasing the continuous spheres (4), a sintering process of sintering the degreased continuous spheres (4), and a process of degreasing each sphere (3) from the sintered continuous spheres (4).
)... is comprised of a sphere separation step.

Therefore, the round bar forming process includes a mixing process in which ceramic powder and a binder are mixed in a kneader, and a mixture (5) of the kneaded ceramic powder and binder in an extrusion molding machine shown in FIG. 6) and extrusion molding step. The binder is mainly a binder showing high viscosity in a low concentration aqueous solution such as tragacanth rubber, Me (methyl cellulose), or PVA (polyvinyl alcohol), to which a plasticizer and a lubricant are added. As an example of mixture (5), ceramic powder 10
0 parts to 33 parts of water (however, 2 to 3 parts of n-butyl alcohol
Include 3 copies. ) and 5.0 parts of MC and wax emulsion.

1.0 part of stearic acid emulsion (solid content: 40%) and 1.0 part of stearic acid emulsion (solid content: 20%). As another example, 78 parts of water (replaced 2 to 8 parts of n-butyl alcohol with water), 12 parts of MC, wax emulsion (4ON concentration)
7 parts of stearic acid emulsion (20 x 11 degrees), 3 to 3.5 parts of glycerin or petroleum were sufficiently mixed in a kneader to form a dough, and then ceramic powder was mixed to form a mixture of 70 to 70 parts.
75 parts and 25 to 30 parts of the binder are uniformly mixed again in the kneader, and the mixture (5) is then transferred to the extrusion molding machine (6).
consists of a cylinder (7) filled with the mixture (5) and a piston (8) slidably inserted into this cylinder
), and this piston (8) is driven by a drive '1M (not shown).
By pressing in the direction of arrow (9) by the mechanism, the mixture (
By extruding 5), a round bar (1) is obtained.

Furthermore, the rolling machine (2) used in the rolling process is
A pair of rollers a1) and ae provided close to each other,
A rotational drive mechanism (not shown) that rotates these rollers in the same direction (arrow (M) direction) and at the same speed, and a roller U
, (Ia) has a pair of support plates Q3. (13) that support and guide the round bar (1) while sandwiching it between them. A rolling groove I, 09 having a semicircular or partially arc cross-sectional profile is spirally carved in the rolling groove #I.

ae is set so that the lead angle is on the entrance side so that the volume of the round bar (1) bitten at the entrance of rollers αυ, α2 is equal to the volume of the continuous sphere (4) coming out from the exit of rollers αυ, (14). In addition, the roller αυ, the circle, and the round bar (1) are not in one plane, but are inclined so that the round bar (1) is fed. Therefore, the support plate (roll the round bar (1) sandwiched by IL (13) in the direction of the arrow (N)), C12
When loaded into the inlet of 1, the round bar (1) is deformed into a smaller and smaller cross section, and from the exit of the roller circle, 04, the sphere (3)... is formed by a small bridge aQ... A continuous sphere (3) shaped like a connected skewer dumpling appears. This continuous sphere (3) is a so-called green molded body.

Next, in the degreasing process, the binder filled with gold in the continuous sphere (3), which is a green molded body, is removed and vaporized and decomposed by heating in a degreasing furnace.

As an example of the degreasing conditions, as shown in FIG. 7, 1%N.

After raising the temperature to 555° C. at a rate of 3 C per hour in (nitrogen) gas, this temperature was maintained at 555° C. for about 1 hour, and the mixture was further cooled in a furnace.

Further, in the sintering step, the degreased continuous sphere (4) is sintered at 1650° C. in a sintering furnace.

Then, the sphere separation step involves separating the continuous spheres (4) after sintering.
For example, hit the bridge with a hammer etc. to create a bridge (IQ...
Separate each sphere (3) using the portion as a boundary. Power X
After the bridge (I) remaining on each sphere (3)...
The trace portion of Q... is removed using, for example, a grinding wheel to obtain a coarse sphere.

As described above, in the ceramic sphere manufacturing method of this embodiment, a round bar (1) is formed into a sphere using a rolling machine (2). As a result, the processing accuracy of the resulting sphere (3) is high, and there is no band-like part that is created when pressing using a mold, so the amount of finishing required later can be reduced. Of course, the material yield is also improved. In addition, productivity is improved because the rolling work can be easily automated.

In addition, in the rolling process of the above embodiment, the round bar (1) is
Although they are connected by bridge αQ..., the rollers (
11) If a sharp blade is provided on the exit side of Qa, the sphere (
3)... can be separated one by one. By doing so, the sphere separation step can be omitted.

Furthermore, the round bar (1) may be formed by foam casting, rubber pressing, or the like. Furthermore, degreasing may be performed during the temperature raising process in the sintering process.

〔Effect of the invention〕

In the method for manufacturing a ceramic sphere of the present invention, a round bar is rolled to form a sphere. As a result, not only it becomes possible to process the sphere with high efficiency and high precision, but also the material yield is improved and post-processing is reduced, which contributes to reducing production costs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a round bar obtained in the round bar forming process of the method for producing ceramic spheres according to an embodiment of the present invention, and FIG. 2 is a cutaway perspective view of essential parts showing a rolling machine used in the rolling process. , Figure 3 is a cross-sectional view of the roll axis in Figure 2, Figure 4 is a diagram showing a continuous sphere obtained in the rolling process, and Figure 5 is a diagram for forming the round bar shown in Figure 1. FIG. 6 is a sectional view showing rolling grooves provided on the roll shafts of FIGS. 2 and 3, and FIG. 7 is an explanatory diagram of the degreasing process. (1)...Round bar (rod-shaped body). (2)...Rolling machine. (3)...Sphere. (4)...Continuous sphere. Agent Patent Attorney Noriyuki Chika Yudo Hikaru Matsuyama

Claims (2)

[Claims] (1) In a ceramic sphere manufacturing method in which a sphere is formed from a rod-shaped body made of a mixture of ceramic powder and a binder, a continuous sphere is formed by rolling the rod-shaped body and connecting a plurality of the spheres in a skewer shape. A rolling process for forming a sphere, a sphere separation process for separating continuous spheres obtained by this rolling process, and a degreasing and firing process for degreasing and firing the spheres obtained in this sphere separation process. A method for manufacturing a ceramic sphere characterized by: (2) In a ceramic sphere manufacturing method of forming a sphere from a rod-shaped body made of a mixture of ceramic powder and a binder, a continuous sphere is formed by rolling the rod-shaped body and connecting a plurality of the spheres in a skewer shape. A rolling step for forming a continuous sphere, a degreasing and firing step for degreasing and firing the continuous sphere obtained by this rolling step, and a sphere separating step for separating each sphere constituting the degreased and fired continuous sphere. A ceramic sphere manufacturing method characterized by: