JPS6297804A - Manufacture of complicate shaped product such as ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is applicable to ceramics, etc., in which products with particularly complex shapes are produced by injection molding using powder raw materials such as ceramic powder, metal powder, or glass powder. The present invention relates to a method for manufacturing products with complex shapes.

"Conventional technology" Conventionally, powder raw materials such as ceramic powder, metal powder, and glass powder are usually blended with a binder mainly composed of paraffin wax to give fluidity and then injection molded. The green molded body thus obtained is debindered, and then placed in a high-temperature kiln and sintered to obtain a sintered product.

Methods for molding ceramic powders, metal powders, etc. include slurry casting, pressing, extrusion, and injection molding, but among these, methods for molding products with complex shapes include: There are slurry casting methods and injection molding methods.

The latter injection molding method is the most industrially important technology as a method for efficiently molding a large amount of molded bodies with high precision and uniform strength distribution.

For this reason, it has come to be widely used, for example, in the manufacture of turbochargers, which are parts of automobile engines.

By the way, in order to mold green molded bodies such as ceramics with complex shapes using this injection molding method, the molded bodies must have a shape that can be easily removed from the mold. This is a prerequisite.

For example, in order to take out the green molded body of the turbocharger rotor, a movable core is placed between many blades, and as the mold is opened and closed, the many cores are removed.
At the same time, it is necessary to move it radially. Furthermore,
If the shape is like a combination of two cup-shaped objects, such as the sub-combustion chamber of an engine, it is difficult to obtain a green molded object by injection molding.

Therefore, products with such shapes are divided into shapes that can be injection molded, and after obtaining green molded bodies separately, they are sintered, and the sintered crystals thus obtained are used as adhesives or wax. The product is made by bonding using a bonding agent or the like. Alternatively, during injection molding, an insert that can be removed after molding is inserted in advance to obtain a green molded body, and then the insert from the green molded body is removed by heat or alkali melting to obtain a sintered product. .

In other words, these methods require many steps,
Due to the labor involved, the product cost is high.
There were many problems, including problems with the reliability of bonding strength and product variations.

The present invention seeks to solve these problems.

"Means for Solving the Problems" The present invention provides fluidity by mixing an organic binder with powder raw materials such as ceramic powder, metal powder, glass powder, etc., and then injection molding the mixture to produce a green molded body. get.

Next, a plurality of green molded bodies are combined and fused to form a green molded body having a complicated shape.

Next, the organic binder is removed from this green molded body having a complicated shape, and further sintering is performed to obtain a complicated shaped product such as ceramics.

``Function'' Generally, when injection molded products such as plastics are bonded together using adhesives, the strength of the bonded parts and the state of deterioration affect the characteristics of the product, such as impact strength and durability. do.

However, when a green molded body is fused as in the present invention, the strength of the fused portion does not affect the strength or deterioration state of the sintered body.

Therefore, a sintered body obtained by fusing a plurality of green molded bodies is no different from one obtained from a green molded body that is integrally injection molded from the beginning.

This means that when sintered bodies are joined together, the quality of the joining immediately greatly affects the characteristics of the product, but in the case of fusion of green molded bodies as in the present invention, the product becomes the product as it is. (This is because the product is sintered after one step of removing the binder.

"Example" One embodiment of the present invention will be described.

Using a compound that is a mixture of ceramic powder, metal powder, etc., and an organic binder such as wax, each green molded body is molded by injection molding in separate molds or molds with different cavities.

Next, a plurality of these green molded bodies are combined into a desired product shape, and the end faces are heated and fused.

Methods for this fusion include friction welding using ultrasonic waves, which is normally used for plastic fusion, heating and melting the respective end faces with a hot plate, and fusing the end faces using microwaves. local heating of the end face using an electron beam, etc., and then fusion.
There are various methods such as. In some cases, there may also be a method in which a molded article previously injection molded using the same compound is inserted into a mold, and then the molten compound is molded and fused.

In this way, after obtaining a complex-shaped green molded body formed by combining a plurality of green molded bodies, this is placed in a degreasing furnace, the binder is removed by a predetermined method, and then this degreased body is is placed in a kiln and sintered.

The temperature for debinding is usually 400-600°C, and the sintering temperature is, for example, 1650°C for alumina, 1700-1850°C for silicon nitride, and 2000°C for silicon carbide.
~2200°C.

In the case of reactive sintering, sintering is performed under an atmosphere such as nitrogen gas, and in the case of powder metal, sintering is performed under a reducing atmosphere such as hydrogen gas.

It is desirable that the fused portion be fused to such an extent that the boundary surface cannot be discerned. If the fusion operation is poor and the concentration of the powder to be sintered, such as ceramics, changes greatly at the interface, cracks or differences in dimensional shrinkage will occur during sintering.

During fusion, the pressure applied to each part is sufficient to maintain the product, and no special high pressure is required.

Although the heating temperature varies depending on the composition of the binder, it is usually about 90 to 200°C, and it is better not to volatilize or foam the binder by heating excessively.

The heating atmosphere should be set to avoid oxidative deterioration of the binder.
Considerations such as creating an inert gas atmosphere are usually not required.

If dimensional changes such as swelling of the fused parts occur due to fusion, the dimensions should be corrected in advance using a known material such as sandpaper while the green molded body is still in place.

"Effects of the Invention" According to the present invention, a product with a complex shape, which has hitherto been impossible to injection mold at once, can be divided into two or more parts and then injection molded. Thereafter, by heating and fusing them, a green molded body with a complex shape can be easily obtained, and this green molded body can be easily obtained by removing the binder and sintering the green molded body using a conventional method. be able to.

Therefore, compared to the conventional method of obtaining complex-shaped products by joining sintered parts together, or by pre-machining and finishing the pre-sintered parts, The fusion process used for plastics etc. can be easily applied as is, and not only does it require less manpower and fewer steps, but it is also possible to manufacture highly reliable products at a lower cost. becomes.

Claims (1)

[Claims] An organic binder is mixed with a powder raw material such as ceramic powder to give fluidity, and this is injection molded to obtain a green molded body.Next, multiple green molded bodies are combined and fused together to form complex shapes. A method for manufacturing complex-shaped products such as ceramics, which comprises forming a green molded body, then removing an organic binder from the green molded body having a complicated shape, and further sintering the green molded body.