JPH0376603A - Press molding method for ceramics - Google Patents

Abstract

PURPOSE:To improve the strength, size stability and productivity of ceramic- molded products by performing the vacuum-extrusion of a ceramic material after kneading said material, cutting the extruded material into the form of blocks and putting the blocks in a mold to be press-molded into a predetermined shape. CONSTITUTION:After a ceramic material has been kneaded, the kneaded ceramic material is vacuum-extruded and cut to form blocks which are then put into a mold to be press-molded into a predetermined shape. The ceramic material may be composed of any kind of suck materials as alumina, silicon carbide, silicon nitride and zirconia, and when the kneading is performed before estrusion, a necessary and general sintering assistant and a binder for molding are added to such raw material powder, and further, water or an organic solvent is added thereto be sufficiently and uniformly kneaded by a kneader or the like. By this method, the separation of a molded product from the mold can be carried out easily, and the molded product which has strength enough to cause no trouble in handling the same and is easy to be dried without leaving voids can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a ceramic molded body for sintering, and more particularly to a method for wet press forming a complicated shaped body.

[Conventional technology]

After molding ceramic powder, etc., it is sintered to produce sintered bodies such as mechanical parts.However, in order to eliminate raw processing after molding and grinding after sintering as much as possible, it is necessary to produce sintered bodies into final products. It is desirable to keep the shape close to that of the final product, and it is required that the formed body before sintering be shaped as close to the final product shape as possible after sintering.

Methods for forming such a formed body include die press molding and slurry casting.

It is difficult to produce complex shapes with die press molding.

In addition, in the slurry casting method, a slurry composed of sintering powder, an organic binder, and a solvent such as water or an organic solvent is poured into a plaster mold, etc., and the liquid in the slurry is sucked into the plaster mold, etc. to form the desired shape. This is a method of molding. There is also a method of pressurizing the slurry injected at this time.

That is, this method is a method of removing liquid from the slurry using a plaster mold, and includes a slurry casting method, a pressure casting method, and the like.

In particular, the pressure casting method has the advantage that it can be easily molded even if it is complex.

[Problem to be Solved by the Invention J] However, the formed body formed by the pressure casting method has low strength in a shape-retaining state. Therefore, it is difficult to quickly remove the molded product from the plaster mold, but it is necessary to remove the molded product from the plaster mold for drying after molding, which makes handling complicated and requires extreme care. Also, cracks are likely to occur unless drying is done very slowly.

Pressure casting may involve degassing, but air bubbles mixed into the slurry are difficult to remove, and sometimes pores may remain in the molded product.

In view of these problems, it is an object of the present invention to provide a method for obtaining a molded product that can be easily removed from a mold, has sufficient strength so as not to be a problem in handling, is easy to dry, and does not leave any pores. With the goal.

[Means for Solving the Problems 1] The molding method of the present invention, which has been made to achieve the above object, involves kneading ceramic materials, vacuum extrusion molding, cutting to mold blocks, and placing the blocks in a mold. This is a press-molding method for ceramics, which is characterized by press-molding ceramics into a predetermined shape.

Types of ceramics include alumina, silicon carbide, silicon nitride,
Any material such as zirconia may be used. These raw material powders have an average particle size of 104 m or less.

When mixing wires before extrusion molding, add necessary general sintering aids and molding binders to these raw material powders, further add water or organic solvent, and thoroughly and uniformly knead with a kneader etc. .

Vacuum extrusion molding is an extruder that has a vent part with negative pressure in the middle of the extruder, or is equipped with vacuum equipment to reduce the pressure in the middle of the two-stage extruder, which may cause scratches or bubbles in the extruded product. Extrusion molding is performed after removing excess volatile components (water, solvents, etc.) and degassing.Compared to mold molding, the degassing is sufficient and continuous molding is possible, making it an excellent molding method. It is the law. It is generally better to have a vacuum degree as high as possible during vacuum extrusion, but it is necessary to maintain a pressure of at least 300 mmHg or less.

Further, the size of the block after vacuum extrusion molding varies depending on the shape of the final product, but it is preferable that it be close to the shape of a predetermined formed body or have the same volume as the formed body.

[Example 1 Hereinafter, the present invention will be explained in detail with reference to Examples.

To 100 parts by weight of silicon carbide powder with an average particle size of 0.45 μm, 0.14 parts by weight of boron carbide powder, 4 parts by weight of methyl cellulose, and 0.25 parts by weight of water were added, and the mixture was heated in a pressure kneader.
After kneading for 30 minutes in a vacuum extruder, the outer diameter was 19 mm.
A rod-shaped body is molded and further cut into 10 nu, with an outer diameter of 19.
Make a block with a thickness of 10 mm.

Insert this block into the mold shown in Figure 1, 50
It was press-molded into the shape shown in Figure 2 at a pressure of 0 kg/Ctrl'.

After that, when the molded body was taken out from the mold, the shape retention was good.
It was confirmed that there were no problems in terms of strength or dimensions.

Further, as a result of drying the molded product at 120° C. for 24 hours, a strong molded product without cracking, deformation, etc. was obtained.

The molded body was degreased at 800°C for 2 hours, and then heated to 2050°C.
After sintering at 30°C for 3 hours and inspecting the appearance and dimensions, no problems were found and a good sintered body was obtained.

[Effects of the invention] In the dry press molding method, which is a conventional molding method for ceramics, when a simple mold or gusset is used to create a molded object with a complex shape, it is necessary to perform green processing after molding. be. If you try to eliminate raw processing, the molds and tool sets will become complicated, and the equipment costs will be considerable.
Molding is also difficult, and it is even more difficult to ensure uniformity of green density in each part of the formed body, and therefore cracks are likely to occur at step joints and the like.

On the other hand, in the molding method of the present invention, the mold, tool set, etc. can be made simple due to the fluidity of the extruded block, and even with the upper and lower end method, a sufficiently good molded product can be produced without requiring green processing. Therefore, it is possible to easily obtain a uniform molded body with good shape retention, a sintered body without cracks, and a good one-dimensional stability in terms of strength. , it is also very effective in improving productivity.

[Brief explanation of drawings]

FIG. 1 shows a press mold and a block after extrusion molding, and FIG. 2 is a sectional view showing a molded product after molding. l...Dice, 3...Lower punch, 2...Upper punch 4...Block diagram-1

Claims (1)

[Claims] 1. A method for press-molding ceramics, which comprises kneading ceramic materials, vacuum-extruding them, cutting them to form blocks, and placing the blocks in a mold and press-molding them into a predetermined shape.