JP3221227B2 - Casting method of ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining a molded body of ceramics by cast molding, and more particularly to a casting method most effective for obtaining a flat molded body. The shape is not particularly limited. For example,
It is also possible to mold a molded article having a shape having irregularities on the surface.

[0002]

2. Description of the Related Art Conventional methods for obtaining a ceramic molded body include a pressing method, an injection method, a casting method, and an extrusion method.
Among these, the casting method is a molding method suitable for obtaining a large molded product and a complicated molded product by only one molding, and has been established as a manufacturing technique for various products.

[0003] However, since the casting is usually a method of performing molding while slowly and intimately depositing in a wet manner, it is also a fact that it is a very delicate molding method.

[0004] For example, in the case of a plate-shaped molded body, in a conventional manufacturing method, first, an original shape corresponding to a desired shape and size is manufactured,
Based on this, a mold with a cavity formed in the water absorption mold itself is manufactured. When molded using this, moisture in the slurry is absorbed in the vertical direction, but water is absorbed not only in the vertical direction but also on the side surfaces of the product. As described above, since the directionality of water absorption is not constant, stress is likely to remain near the product edge, and as a result, lamination cracks are likely to occur in this portion during drying and firing.
In addition, since the compact immediately after molding contains moisture due to wet molding, this also promotes the occurrence of lamination cracks unless care is taken in drying. Therefore, it is necessary to take sufficient time for drying and to be careful. In particular, since lamination cracks are likely to occur on the side surface of the product, drying for a long time and removing the binder are essential. This makes the process longer and reduces productivity.

Hereinafter, this phenomenon will be described in detail. Conventionally, when a plate-like material is obtained in the casting of ceramics, fine ceramic powder, or the like, water absorption in the slurry occurs as follows. FIG. 1 shows this state.
First, the central part of the plate absorbs water toward the vertically absorbing water-absorbing plate-like material, and at the same time, the deposition of the powder particles in the slurry goes from the portion near the water-absorbing mold to the inside of the cavity in a layered manner. First, if the water absorption capacity of the upper and lower water absorption molds is the same, the inlaid layers from above and below are united at the center of the cavity, and the molding is completed.

[0006] In general, in the casting of a plate, the arrangement of the slurry inlet, ie, the gate port, is usually located somewhere on the side of the plate. For this reason, since the slurry must be constantly supplied from this location to the center of the plate or the edge portion opposite to the gate, the slurry is normally supplied with pressure to smooth the supply.

However, as the thickness of the deposited layer increases over time, the remaining slurry layer, or supply layer, becomes thinner. As a result, the pressure loss becomes large and it becomes difficult to supply the slurry, and this supply is hardly performed near the end point of the casting. As a result, at the end point of the casting, that is, immediately before the joining of the inlaid layer, the joining is not performed by a single inlaid layer from the vertically absorbent water-absorbing plate-like material, but there is a large amount of voids due to the remaining slurry. It becomes united by a proper inking layer.

For this reason, the united portion has a structure in which internal stress is likely to remain due to the fact that bubbles contained in the slurry are likely to collect, and this portion has a structure in which defects such as cracks are likely to enter. ing. Generally, the crack generation is prevented by increasing the particle size of the powder or improving the water absorption of the mold.

However, at the outer peripheral portion of the cavity, that is, at the side surface portion, water absorption also occurs from the side surface, so that the structure is different from the up-down two-way inlaid structure such as the central portion.

Referring to FIG. 2, the mechanism of occurrence of lamination crack in the conventional casting method will be described. FIG.
As shown in (a), the water absorption of the slurry occurs in the three directions of the upper and lower sides and the lateral side of the side surface in the side part,
For this reason, the united layer on the side surface of the molded article is dispersed in two directions, obliquely upward and obliquely downward, as shown in FIG. 2B, and both upper and lower edges forming a right angle of the united part are shown in FIG. 2C. As described above, since the thickness of the inking layers on both sides is almost nil, the structure is very weak against tearing due to residual stress in this portion. For this reason, as shown in FIG. 2 (d), lamination cracks very often occur from this portion in a straight line along the product side surface.

This tendency becomes stronger as the size of the product increases. For this reason, the product is manufactured to be considerably large in consideration of the lamination crack, and the product is obtained by grinding the lamination crack portion by post-processing or the like. , Which causes the raw material yield to drop significantly.

To reduce the residual stress as much as possible, it is effective to lower the pressure at the time of molding, but the productivity is reduced because the molding time becomes longer. Also, due to the residual stress, sufficient attention must be paid to the drying of the molded body, and the productivity is degraded due to the drastically increased drying time.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel casting method for a ceramic which can prevent the occurrence of lamination cracks in the vicinity of the side face in the conventional casting method and can shorten the drying time. It is to provide a method.

[0014]

Means for Solving the Problems The present inventors have conducted intensive studies on a casting method as a method of forming ceramics, and as a result, by preventing water absorption on the side surface, the forming due to the uneven thickness of the deposit layer. It has been found that the residual stress of the body hardly remains, and as a result, lamination cracks hardly occur, and therefore, the drying time can be shortened, and the present invention has been completed.

That is, according to the present invention, the non-water-absorbing material different from the specifier of the cavity portion (product portion) is used because the whole cavity formed in the molding die absorbs water, which is performed by the conventional casting method. It is characterized in that a spacer is installed or an inner frame made of a non-water-absorbing elastic material such as rubber is installed on the inner surface of a conventional spacer to prevent side water absorption.

Further, since the rubber frame has good mold release from the spacer, it is effective to take out the molded body smoothly.

Hereinafter, the present invention will be described in detail.

The present invention is characterized in that the molding can be carried out with almost no change in the conventional manual for the casting by improving or adding a part of the cavity. A conventional casting method will be described with reference to FIG.

In the conventional casting method, in the case of a plate, molding is usually performed using two water absorbing molds (1 and 2 in FIG. 3). One is a flat water-absorbing mold (1 in FIG. 3), and the other has a cavity slightly larger than the product size manufactured in consideration of shrinkage by sintering from the desired product shape and size is dug in the center of the mold. With a water absorption plate having a structure (2 in FIG. 3), in a normal casting, a gate (3 in FIG. 3) is installed on one of the molding plates so that slurry can be supplied into the cavity. The two forming plates are combined, a slurry is supplied, and forming is performed.

The casting method according to the present invention will be described with reference to FIG.

In the present invention, the conventional water-absorbing mold having a cavity (2 in FIG. 3) is formed into the same shape (1 'in FIG. 4) as the flat-shaped water-absorbing mold (1 in FIG. 3). Instead, a non-water-absorbing spacer (2 in FIG. 4) is formed by boring a material having appropriate strength, such as plastics, into the cavity between the two water-absorbing molded plates.
It is characterized in that a non-water-absorbing frame (3 in FIG. 4) is provided around the cavity and sometimes made of an elastic material such as rubber around the cavity to prevent the absorption of moisture from the side surface. Further, the rubber frame has an effect that molding is completed and a molded body still containing a large amount of water can be easily taken out.

In the casting method according to the present invention, similarly to the conventional method, a gate (4 in FIG. 4) is installed in one of the water absorption molds so that slurry can be supplied into the cavity, and then two water absorption molds are provided. The molds are combined, and a slurry is supplied to perform molding.

According to the cast molding method of the present invention, not only the plate-shaped molded body shown in FIG. 4 but also the conventional cast molding method as illustrated in FIG. A complicated molded body can be molded by a casting method as shown in FIG.

That is, the upper water absorption type shown in FIG.
By using a water-absorbing mold having a complicated shape as shown in (1), it is possible to produce a molded body as shown in FIG.

The molded body and the sintered body obtained by the method of the present invention hardly have lamination cracks on the side surface as in the prior art. This is because the absorption of water in the side surface has been eliminated, so that the water absorption is also in the up and down directions in the side surface portion of the molded body, so that residual stress due to the anisotropy due to the three-way water absorption in the side surface portion like the conventional molded body hardly occurs. It is thought that it is.

As a result, a molded product having a size much larger than that of the conventional method can be fired without cracks, and the molding can be performed at a very small size of a desired product, thereby greatly improving the yield of the molded product. .

The material of the spacer may be any material as long as it has a certain strength and has a shape-retaining property. For example, in the case of plastics, polyvinyl chloride, polyethylene, polypropylene, acrylic, etc. are sufficient, but engineering plastics such as polycarbonate and nylon are more preferable. Stainless steel for metal,
Any material such as iron, copper, and aluminum may be used, but stainless steel or aluminum is preferable in consideration of workability and durability. In addition, wood, rubber, ceramics and the like can be used. Although this material is sufficient to be non-water-absorbing, there is no problem even if it is the same material as the porous mold used for molding.

The material of the frame surrounding the cavity is preferably elastic, and for example, rubber is optimal. Various rubbers such as silicone, urethane and butadiene are conceivable, but a method of curing a liquid material is the most effective since it must be easily manufactured to conform to the product shape.

As a water-absorbing molded plate, gypsum is usually used in many cases, but recently, high quality porous resins, porous metals, and the like have been made, and any of them can be used.

[0030]

According to the casting method of the present invention, it is possible to obtain a molded article having a very small distortion even from a molded article which has been liable to have a lamination crack due to uneven thickness. As a result, molding can be performed at a higher pressure as compared with conventional casting, so that the molding time is shortened and the productivity is improved. In addition, large-sized molded products, which were conventionally difficult to manufacture, can be manufactured.

In addition, even if it is not a flat molded body but has a complicated shape as shown in FIG. 5, for example, which cannot be molded by the conventional technique, it can be manufactured with a little contrivance (FIG. 6). Thus, in the conventional method, although a lamination crack was generated on the side surface, it was possible to obtain a molded product that could not be molded.

In addition, since residual stress is hardly generated inside the molded product, drying and debinding can be considerably simplified as compared with the conventional molded product, so that the productivity is improved.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 In forming a flat plate having a length of 300 mm, a width of 150 mm and a thickness of 12 mm, a length of 400 mm and a width of 250 m
A vinyl chloride flat plate having a thickness of 12 mm and a thickness of 12 mm was prepared, and a bored cavity having a length of 310 mm and a width of 160 mm was opened therein. Around this, a thickness of 12.5 mm and a width of 5 mm were formed.
Was provided with a silicone rubber frame.

Apart from this, a length of 400 mm and a width of 250 mm
Two flat porous molds each having a thickness of 80 mm and a thickness of 80 mm were made of gypsum, and one of them was provided with a gate opening. This 2
A vinyl chloride spacer in which a rubber frame is set is sandwiched between two water-absorbing molds, and is fixed by a mold clamping machine. Then, 100 parts of zirconia powder, 25 parts of water, and 0.1 part of the weight of the zirconia powder are added. 5 wt% polycarboxylic acid dispersant, 1.0 wt
% Of an acrylic water-based binder was added, and a slurry prepared by mixing and pouring was poured into the mixture, and the mixture was pressurized to 5 kg / cm ² to perform cast molding.

After the molding was completed, the molded body was taken out, dried at room temperature for 2 days, and then heated at a rate of 5 ° C./hr.
The binder is removed by holding at 500 ° C. for 2 hours, and then the temperature is increased in air at a rate of 50 ° C./hr.
Sintering was performed by holding at 1500 ° C. for 2 hours.
The size of the obtained sintered body is 240 × 120 × 9.6 mm
Met. When this sintered body was checked with a fluorescent test solution, no noticeable large lamination crack was generated.

Example 2 In forming a flat plate having a length of 600 mm, a width of 250 mm and a thickness of 10 mm, a length of 800 mm and a width of 450 m were used.
m, an aluminum flat plate having a thickness of 10 mm is prepared, and a boring cavity having a length of 610 mm and a width of 260 mm is opened therein. Around this, a thickness of 10.5 mm and a width of 5 mm are provided.
A urethane rubber frame was provided.

Separately, the length is 800 mm and the width is 450
Two flat plate porous resin molds having a thickness of 100 mm and a thickness of 100 mm were produced, and one of them was provided with a gate opening. An aluminum spacer on which a rubber frame is set is sandwiched between the two water-absorbing dies, and is fixed by a mold clamping machine. Then, 100 parts of indium oxide and tin oxide mixed powder, 23 parts of water, and 1 part of 0.5 wt% polycarboxylic acid dispersant, 1.2 wt%
% Of an emulsion-based binder was added, a slurry prepared by mixing and pouring was added, and the mixture was pressurized to 20 kg / cm ² to perform cast molding.

After the molding was completed, the molded product was taken out, dried for 2 days in a humidifier and dried at 3 ° C./h.
r De-bindering is performed by maintaining the temperature at 450 ° C. for 2 hours, and then 25 ° C. in an oxygen atmosphere.
Sintering was performed by maintaining the temperature at a rate of / hr at 1500 ° C. for 2 hours. The size of the obtained sintered body is 745 ×
It was 201 × 8.1 mm. When this sintered body was checked with a fluorescent flaw detection liquid, about two fine cracks, which seemed to be caused by mold release, were found, but no large lamination cracks were seen at all.

Example 3 A master mold as shown in FIG. 5 having an outer diameter of φ180 and a maximum thickness of 20 mm was prepared.
180, 19 mm thick acrylic resin spacer
Was prepared, and a rubber frame was prepared using liquid silicone rubber. Using these, a water-absorbing mold was manufactured using a porous resin as shown in FIG. After embedding a pipe having an inner diameter of φ8 into the side surface of the acrylic resin so as to connect the cavity portion to the outside of the mold, a joint is attached so that the pipe can be connected to a hose from a slurry tank. After combining these molds and fixing the molds with a mold clamping machine, 100 parts of aluminum oxide, 20 parts of water, and 0.2 wt.
% Of a carboxylic acid-based dispersant and 0.5 wt% of an emulsion-based binder were added thereto, and the mixed and blended slurry was fed under pressure and cast at a pressure of 10 kg / cm ² .

After the molding was completed, the molded body was taken out, dried at room temperature for 3 days, and heated at a temperature of 3 ° C./hr for 50 days.
Debinding is performed by holding at 0 ° C. for 2 hours.
Thereafter, the temperature was raised in air at a rate of 100 ° C./hr,
Sintering was performed by holding at 600 ° C. for 2 hours. The size of the obtained sintered body is φ155 and the maximum thickness is 17.2 m
m. When the same product was made in total of 5 pieces and these sintered bodies were checked with a fluorescent flaw detector, fine cracks were slightly observed, but no large lamination cracks were found in any of the products.

Comparative Example 1 In molding a flat plate having the size shown in Example 1, a casting mold was produced by a conventional method as shown in FIG. 3, and the obtained molded body was dried at room temperature for 4 days. Then, binder removal and firing were performed in exactly the same manner as in Example 1 to obtain a sintered body. When this was checked with a fluorescent test solution, a lamination crack having a crack width of 0.3 mm and a length of 150 mm was found on the side surface of the sintered body.

Comparative Example 2 In molding a flat plate having the size shown in Example 2, a casting mold was produced by a conventional method as shown in FIG. 3, and the obtained molded body was humidified for 3 days. It was dried, debindered and fired in exactly the same manner as in Example 2 to obtain a sintered body. When this was checked with a fluorescent test solution, the crack width was 0.5 m on both sides in the longitudinal direction of the sintered body.
Lamination cracks of m, 450 mm, 0.7 mm and 250 mm in length had occurred.

Comparative Example 3 In molding a complex shape having the size shown in Example 3, a casting mold according to a conventional method as shown in FIG. 7 was manufactured. On the other hand, the dried compact had many cracks radially from the vicinity of the gate. When this was subjected to binder removal and firing, this tendency was even more intense and almost two.

[Brief description of the drawings]

FIG. 1 is a view showing a state of water absorption in a conventional casting method.

[Explanation of Signs] 1 Gate port 2 Water absorption direction a) Casting start b) During forming c) End of forming

FIG. 2 is a view showing a mechanism of lamination crack generation in a conventional casting method.

[Explanation of symbols]

 Reference Signs List 1 inlaid layer 2 slurry layer 3 united layer 4 inlaid layer thickness 5 lamination crack a) direction of water absorption of slurry b) united layer c) side inlaid layer thickness d) lamination crack

FIG. 3 is a view showing a conventional casting mold.

[Explanation of symbols]

 1 Water absorption type (flat type) 2 Water absorption type (cavity digging type) 3 Gate port

FIG. 4 is a view showing a casting mold of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water absorption type (flat type) 1 'Same as above 2 Spacer 3 Rubber frame 4 Gate port

FIG. 5 is a view showing an example of a molded product that cannot be molded by a conventional casting method.

FIG. 6 is a view showing a method of casting the molded article shown in FIG. 5 in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water absorption type 2 Spacer 3 Rubber frame 4 Cavity 5 Gate

FIG. 7 is a view showing a conventional casting method used in Comparative Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water absorption type 2 Cavity 3 Gate opening

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B28B 1/26

Claims (3)

(57) [Claims] 1. A method for casting a ceramic, in which a molded body is obtained by casting a ceramic slurry into a casting mold, wherein a void is provided inside a flat plate, and a non-water-absorbing elastic body is provided around the void. On the upper and lower surfaces of a flat plate with a frame,
A method of casting and molding ceramics, comprising using a mold formed by stacking molds having water absorbency , and pressurizing and supplying a ceramic slurry . Wherein the material of the flat plate, plastic, wood, cast molding method of a ceramic according to claim 1 are those selected from metal. 3. A process according to claim surface facing the gap portion of the mold with a water absorbability, characterized in that a plane 1 or claim 2
3. The method of casting ceramics according to 1.