JPH0829533B2 - Ceramic columnar article manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Definitions The terms used in this specification are defined as follows.

Ceramic powder: Raw material powder for manufacturing ceramics.

Ceramic slurry: A slurry obtained by adding water and, if necessary, a resin component such as a dispersant and a binder to ceramic powder, which is a raw material slip in the slurry casting method.

Ceramic molded product: A product obtained by molding a molding composition obtained by adding water and, if necessary, a resin component such as a dispersant to a ceramic powder.

A sintered body (ceramics) is obtained by sintering this.

Unidirectional solidification method: Only some surfaces are made of water-absorbing material,
The rest is a slurry casting method that uses a mold made of water-impermeable material. Water absorption, i.e. solidification, occurs in only one direction.

[Industrial applications]

The present invention relates to a method for manufacturing a ceramic columnar body.

[Conventional technology]

The columnar ceramic molded body can be manufactured by any molding method such as a press molding method, an extrusion molding method, an injection molding method, and a casting molding method. The press molding method has a wide range of production from small items to large items, but generally requires finishing such as lathe processing and milling, and the more complicated the shape, the more various finishing processes are required. The extrusion molding method is advantageous for molding simple columnar materials such as columnar and prismatic materials; the injection molding method is often applied to the production of complicated shapes, but in both cases, binder and plastic materials are used. Since a large amount of resin such as an agent is added for molding, a lot of technical know-how is required centering on molding conditions (temperature, pressure, etc.) and degreasing conditions. The thicker (larger) the more difficult it is to obtain a ceramic having a predetermined size and shape. The cast molding method has many merits such as that it is possible to mold a complicated shape or a large-sized product without finishing processing with simple and inexpensive equipment, and to shorten the degreasing step because the added resin content is small. However, there are also problems.

That is, in the case of obtaining a solid cast molding using a slurry of ceramic powder, a dispersant, a binder, water, etc. are added to the ceramic powder to adjust the pH and the viscosity, and the mixture is sufficiently mixed to absorb water. Molding is performed by casting under pressure or normal pressure into a cavity having a desired shape of a porous molding die. However, if the molding die is a non-elastic porous body such as gypsum, especially if the shape becomes complicated or the wall becomes thicker, the molding including the pouring gate will make the sludge evenly adhere Ingenuity is required in the design of the mold, and in the case of a shape that is likely to be broken or chipped during demolding, a multi-divided molding mold must be used to facilitate demolding. When the multi-divided type is used, naturally, burrs are generated on the molded body, which causes sharpness, which has a great adverse effect on the yield of products. For this reason, there is a demand for a method of obtaining a molded article having a complicated shape without using a split mold as much as possible.

A unidirectional solidification method has been proposed as an improved method of the conventional slurry casting method. (JP-A-60-92806,
60-230804, 61-252102, 61-274903, etc.). However, the present inventors have found that when this method is used, even if a columnar molded body is obtained, the ceramic obtained by sintering it does not have a columnar shape. That is, a molding die of a complex shape part of the product is manufactured by a water-impermeable soft rubber mold, and a molding die of a flat part of the product or a simple shape part similar to that is formed of gypsum or a metal having porosity, It is made of resin and the sludge is dehydrated at this part, preventing the formation of burrs and making use of the elasticity of rubber while avoiding the multi-division mold of the complicated shape part. The molded product can be taken out smoothly. As a method of making a molding die, after making an actual model (referred to as a prototype or master) that takes into account the shrinkage rate due to drying and sintering, pour liquid rubber etc. into the complicated shape part and plaster etc. into the simple shape part. After that, it is convenient to cure it to obtain a mold.

However, when the present inventors attempted to manufacture a ceramic columnar body by this unidirectional solidification method, it was found that there were the following fatal problems. That is, in the case of the unidirectional solidification method, the farther from the surface of the water-absorbent material, the smaller the filling density becomes, and therefore the shrinkage in sintering tends to be remarkable. There is a strong tendency. For this reason, the dimensional accuracy of the sintered product is poor and, for example, when a cylindrical product having a uniform diameter is used as a prototype and a molded product is sintered and the resulting product is sintered, the diameter of the upper bottom of the columnar product becomes smaller than the diameter of the lower bottom. Occurs. This is because the density of the sintered body is uniform, but as described above, the density of the molded body becomes smaller as it goes to the upper bottom portion, so that the shrinkage ratio becomes larger at the upper bottom portion and smaller at the lower bottom portion. As a result, the product is tapered as shown in FIG.

The angle of this taper tends to increase as the product becomes larger. For this reason, finish grinding must be performed if necessary, but it is very troublesome.

Therefore, the inventors of the present invention considered the taper angle generated after sintering in advance, produced a prototype having a taper in the opposite direction, produced a molding die based on this prototype, and performed cast molding. As a result, it was found that a columnar product having a uniform diameter was obtained. However, it is not always impossible to produce a prototype having a slight taper for a simple columnar article, but it was extremely difficult to produce this prototype for a complex article.

[Problems to be solved by the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, that is, to provide a method capable of easily producing a ceramic columnar article with good dimensional accuracy even if the shape is simple or complicated. To do.

[Means for solving problems]

The gist of the present invention is to: (a) manufacture a molding die in which a surface other than the lower bottom surface is made of a water impermeable material by a columnar mold; (b) the lower bottom surface is made of a water-absorbing material; Using the mold made of the mold of the water-impermeable material obtained, a ceramic molded body is manufactured by a slurry casting molding method, and the molded body obtained in (c) and (b) is sintered. Then, a sintered body is manufactured, and the sintered body obtained in (d) and (c) is placed with the larger bottom face up and the smaller bottom face down, and this is used as a prototype for other than the bottom face. A mold whose surface is made of a water-impermeable material is manufactured, and (e) a mold whose bottom bottom surface is made of a water-absorbent material and the rest is made of a water-impermeable material mold obtained in (d) and ( Using a ceramic slurry of substantially the same composition as used in b), a ceramic by a slurry casting method. Manufacture of a molded body, and manufacturing of the ceramic columnar article, which is performed by sintering the molded body obtained in (f) and (e) under substantially the same sintering conditions as in (c) to manufacture a sintered body. On the way.

This method is a method of obtaining a sintered body in two steps, and since the shrinkage must be considered twice, the size of the prototype becomes large, but it can be widely applied to a columnar article having a complicated shape.

According to the present invention, it is possible to manufacture not only simple shapes such as a cylinder, a triangular prism, and a square pillar, but also a complicated shape that can be used, for example, as a gear or a die. The columnar mold used in the above (a) may have the same shape as the target ceramic columnar body (a similar shape may be used in consideration of finishing the sintered body by grinding and polishing). In some cases.), (C) and (f) are shrunk by two times of sintering, so the size of the prototype must be set in consideration of this shrinkage allowance. The material of this prototype may be, for example, any of metal, wood, synthetic resin, etc., but in order to obtain a ceramic columnar article with good dimensional accuracy and surface accuracy, the surface is less likely to be scratched, and dimensional accuracy, etc. may be increased. Metal is good because it can be done.

The composition of the ceramic slurry in (b) and (e) and the sintering conditions in (c) and (f) must be substantially the same as each other. Otherwise (f)
This is because a columnar object with good dimensional accuracy cannot be obtained. The ceramic powder in the ceramic slurry may be any of alumina, zirconia, mullite, silicon nitride, silicon carbide, etc. to which the slurry casting method can be applied. Components and composition other than ceramic powder in the ceramic slurry in (b) and (e), and (b)
For the sintering in and (f), a conventional slurry casting method and sintering conditions may be selected depending on the type of ceramic powder and the composition of the ceramic molded body.

The water-absorbent materials used in (b) and (e) are gypsum and metal having continuous voids, which are commonly used in the slurry casting method,
A synthetic resin or the like may be used. This material in (b) and (e) does not necessarily have to be of the same kind, but there is no reason to be of another kind. Rather, it is easier to use the same kind of material because the shrinkage rate and the like become the same.

In (a) and (d), the material on which the prototype is placed when making the water-impermeable mold may be any material having a flat surface, but only using a water-absorbing material, Can be used as it is in the following (b) and (e).

The water-impermeable material in (a) and (d) may be any one as long as the cavity maintains a columnar shape in the following (b) and (e). (However, it is not necessary that the ones in (a) and (d) are the same kind.) However, if this is made of soft rubber, as described above, the prototype has a complicated shape and the molding die is multi-divided. Even if it is not a mold, it is possible to easily take out the ceramic molded body in the prototype or (b) and (e) without breaking the molding die. Therefore, in (b) and (e), burrs, cracks, chips, etc. It is possible to obtain a ceramic molded body without causing (B)
After completion of water absorption in (e) and (e), the molded product shrinks slightly. When the mold is hard, this shrinkage causes the molded body to start releasing from the mold. At this time, if the shape of the molded product is complicated, a part of the molded product comes into contact with the mold, and as the shrinkage progresses, a large stress is applied to this part, so that the molded product is apt to be broken. However, if the mold is a soft one as described above, especially rubber, even if there is shrinkage of the molded product as described above, the rubber mold itself also shrinks with the surface of the molded product and the surface of the mold closely contacting each other. Therefore, the sharpness as described above does not occur. (After completion of solidification, it can be easily removed from the forming die without damaging the surface of the forming body.) Further, in (d) and (e), the forming die for removing the original form or the forming body from the forming die is In the case of a simple shape, the lower bottom surface of the cavity, the prototype, and the molded body are smaller than the upper bottom surface, and the molding die covers the side surface and the upper bottom surface of the prototype or the molded body (see FIGS. 6 and 7). However, if the mold is hard, it cannot be removed from the original mold or molded product without breaking the mold unless it is a multi-divided mold. If the molding die is a soft one, especially rubber, as described above, it can be easily removed even if it has a complicated shape, even if it is not a multi-divided die.

To obtain a mold of the above water-permeable material, for example,
Powdered or liquid synthetic polymer substance, preferably liquid rubber such as liquid silicone rubber, liquid urethane, liquid chloroprene and the like may be poured together with a curing agent around the prototype (side surface and upper bottom surface) to be cured.

As is apparent from the above, the upper bottom surface is smaller than the lower bottom surface by the sintering of (c). In the extreme expression, a frustum is obtained. In (d), this is reversed to form a mold, so that the molded body obtained in (e) using this mold is more likely to shrink due to sintering as it is closer to the larger bottom surface. Thus, in (f), a columnar body with good dimensional accuracy can be obtained.

Example 1 Number of teeth 20, module 1.5, root diameter 26 mm, pitch diameter
A commercially available SUS304 spur gear with a diameter of 30 mm, a tip circle diameter of 33 mm, and a height of 15 mm (Fig. 1) and an acrylic resin cylinder with an outer diameter of 56 mm, an inner diameter of 50 mm, and a height of 30 mm are fully dried circles with a diameter of 100 mm and a height of 80 mm. The spur gear and the cylinder were placed on the gypsum mold so that the respective centerlines of the spur gear and the cylinder came to the centerline of the gypsum mold (FIG. 2).

Next, liquid silicone rubber (Silascon RTV8000 manufactured by Dow Corning Co., Ltd.) containing 1 wt% of a curing agent was thoroughly degassed and then poured into the acrylic cylinder (FIG. 3).

After the rubber was cured, the prototype gear was taken out, the ceramic slurry pouring port, that is, the gate was cut with a cutter at the center of the upper bottom surface of the obtained rubber mold, and it was placed again in the center of the plaster mold.

Next, 470 g of zirconia powder containing Y ₂ O ₃ mol% (TZ-3YS manufactured by Toyo Soda Co., Ltd.), polycarboxylic acid type dispersant (A6114 manufactured by Toagosei Co., Ltd., solid content 40 wt%) 5.7 g, acrylic Emulsion binder (WA32 manufactured by Mitsui Toatsu Co., Ltd.)
0. 5.7 g of solid content 40 wt%) and 110 g of pure water were mixed for 16 hours with an alumina ball having a diameter of 15 mm in a pot made of 1 nylon to obtain a slurry. This was thoroughly degassed and poured from the gate (Fig. 4). After the inking was completed, the molded body was taken out from the rubber mold, dried, debindered, and sintered in air at 1500 ° C. for 2 hours. The linear shrinkage of the obtained sintered body was 18.0% at the lower bottom and 18.7% at the upper bottom. The height had shrunk to 12mm.

After flattening the upper bottom by surface grinding, install this surface so as to contact the gypsum mold (Fig. 6), and repeat the operations from the production of the molding mold to the sintering to obtain 2 teeth.
0, module 1.0, root circle diameter 17.3mm, pitch circle diameter 20mm,
A columnar zirconia ceramic spur gear with a tip circle diameter of 22.0 mm and a height of 9 mm was obtained.

Example 2 An internal gear having a number of teeth 14, an outer diameter 99.3 mm, a root circle diameter 79.5 mm, a pitch circle diameter 66.2 mm, a tip circle diameter 56.7 mm, and a thickness 20 mm, which are manufactured by electric discharge machining using SUS304 as a columnar prototype. Alumina powder (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) 3 kg, acrylic dispersant 2 as ceramics slurry
2.5 g (C-34N manufactured by Nippon Kayaku Co., Ltd., solid content 40 wt%),
Acrylic emulsion binder (Mitsui Toatsu Co., Ltd.)
WA320. Solid content 40wt%) 37.5g and pure water 720g were mixed in a 7.5l alumina pot with alumina balls of 25mm diameter for 16 hours; gypsum mold, diameter of 200mm,
Height 100 mm; acrylic resin cylinder, outer diameter 138
mm, inner diameter 130 mm, height 40 mm except that the number of teeth is 14, module 3.5, outer diameter 73.5 mm, root circle diameter 58.8 mm, pitch circle diameter 49.0 mm, tip circle under the same conditions as in Example 1. Diameter 42.0mm,
A columnar alumina ceramic internal gear with a height of 14.8 mm was manufactured.

The alumina sintered body, which was the prototype for obtaining the final product, had a linear shrinkage rate of 13.2% at the lower bottom and 14.7% at the upper bottom, and a height of 17 mm. The taper angles of the lateral lines of the outer side portion, the tooth bottom portion, and the tooth tip portion were 2.5 °, 2.0 °, and 1.5 °, respectively (Fig. 9). It is extremely difficult to produce by the method.)

[Brief description of drawings]

FIG. 1 is a plan view and an elevation view in which the details of the teeth are omitted, showing the positions of the tooth bottom, pitch and tooth tip of the prototype SUS304 spur gear used in Example 1. FIG. 2 is a conceptual diagram showing a state in which an acrylic resin cylinder is placed on a gypsum mold and the prototype is placed therein. FIG. 3 is a conceptual diagram showing a state where liquid silicone rubber is poured into the cylinder in the above state. FIG.
3 is a conceptual diagram showing a state in which zirconia slurry is poured into a rubber mold obtained by curing in Example 1. FIG. FIG. 5 is a conceptual diagram of a sintered body obtained by sintering a molded body obtained from a columnar mold in Example 1. FIG. 6 is a conceptual diagram showing a state in which the sintered body is turned upside down and placed on a plaster mold. FIG. 7 is a conceptual diagram of a molding die obtained by using the sintered body as a prototype. FIG. 8 is a plan view and an elevation view in which the details of the tooth are omitted, showing the positions of the outer side, the tooth bottom, the pitch, and the tooth tip of the prototype SUS304 internal gear used in Example 2. FIG.
FIG. 7 is a diagram showing taper angles of lateral lines of an outer side portion, a tooth bottom portion and a tooth tip portion of a sintered body obtained by sintering a molded body obtained from a columnar mold in Example 2.

Claims (2)

[Claims] 1. A molding die comprising: (a) a columnar mold having a surface other than the lower bottom surface made of a water-impermeable material; (b) a lower bottom surface made of a water-absorbing material; Using a mold made of the mold of the water-impermeable material, a ceramic molded body is manufactured by a slurry casting molding method, and the molded body obtained in (c) and (b) is sintered, A sintered body is manufactured, and the sintered body obtained in (d) and (c) is placed with the larger bottom face up and the smaller bottom face down, and this is used as a prototype, and a surface other than the lower bottom face is prepared. Is manufactured of a water-impermeable material, and (e) a bottom surface is made of a water-absorbent material and the rest is made of the water-impermeable material molding die obtained in (d), and (b) ), Using a ceramic slurry of substantially the same composition as that used in), by the slurry casting molding method A body is produced, and the formed body obtained in (f) and (e) is sintered under substantially the same sintering conditions as in (c) to produce a sintered body. A method for manufacturing a ceramic pillar. 2. The method for producing a ceramic columnar article according to claim 1), wherein in (a) and (d), a molding die made of a water-impermeable material is produced by curing the liquid rubber.