JPH0675857B2 - Huain ceramics manufacturing method - Google Patents

Description

The present invention relates to a method for producing a fine ceramic product such as silicon carbide or silicon nitride.

As one of the methods for producing fine ceramics products, a ceramic raw material powder is mixed with an appropriate resin binder, and if necessary, a viscosity modifier, a plasticizer, and / or a sintering aid, etc. are added, and injection is performed. Make a molded product with a shape close to the final product by injecting it into the mold using a molding machine,
A method is known in which this molded body is gradually heated at a low temperature to decompose or vaporize an organic substance such as a resin binder, and then heated to a high temperature under normal pressure to perform so-called normal pressure firing. This manufacturing method is suitable for mass production because the molded body is obtained by using an injection molding machine and a mold and firing is carried out under normal pressure, and the manufacturing cost is low. When air is injected into the mold, air in the mold may be entrained to form a cavity inside the molded body, and if the mold has a part with a low temperature, the injected molding material may have the above-mentioned low temperature part. Since it does not lose fluidity and the effective injection pressure does not work,
Local cavities may form in the molding. When such cavities occur, the cavities remain even in the subsequent normal pressure firing step, and there is a problem that the strength of the final product is significantly reduced.

The present invention was devised in view of the above, and a step of injecting a ceramic powder mixed with a resin binder to obtain a desired molded body, and a step of coating the molded body with an easily separable film such as silicon rubber. And a step of hydrostatically pressurizing the coated body at a high pressure, a step of removing the coating on the surface of the body that has been hydrostatically pressurized, and the molded body from which the coating has been removed is heated at a low temperature to obtain the resin. The gist of a fine ceramics manufacturing method is characterized by including a step of removing a binder and a step of firing a molded body from which a resin binder has been removed under normal pressure. According to the present invention, the cavity in the molded body, which is a drawback of the conventional method of molding a molded body using an injection molding machine and a mold, is coated with silicone rubber or the like and then hydrostatic pressure is applied. Since the product is obtained by crushing and extinguishing, then removing the coating and performing normal pressure firing in accordance with a conventional method, it is possible to effectively avoid the decrease in strength due to the residual cavity, and to perform injection molding and The use of atmospheric pressure has an advantage that a product having a complicated shape can be provided at low cost.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, fine powders of ceramic raw materials such as silicon carbide and silicon nitride and auxiliary raw materials to which a resin binder and, if necessary, a viscosity adjusting agent, a plasticizer, a sintering aid and the like are added, are fed from the hoppers 10 and 12 into the adjusting chamber 14. Charge and stir evenly. At this time, the ceramic fine powder is preferably a fine powder having an extremely small diameter of about 0.1 μm in order to enhance the sinterability in the subsequent firing step, and it is as high purity as possible to ensure the desired high temperature strength. Is desirable. The molding material produced in the adjustment chamber 14 is sent to an injection molding machine 16 which is known per se, and is injected into a mold 18 prepared in advance to mold a molded body 20. This molded body 20 is formed by injection of the molding material into the mold 18 because air in the mold may be trapped in the mold 18 and when the mold 18 is partially cooled. Due to circumstances such as that the material loses its fluidity in the low temperature portion and the effective injection pressure may not act, a cavity is often formed inside the material. Next, the molded body 20 is sent to a coating station 22, where a water-tight coating that is easy to peel off is applied after silicon rubber or the like. As a coating method, an immersion method can be adopted in addition to the automatic spraying method shown in the drawing or the method using a manually operated coating gun. The molded body 20 whose surface is airtightly coated is charged into the hydrostatic pressure device 24,
Here, it is exposed to a high hydrostatic pressure of about 2000 to 3000 kg / cm ² .
The hydrostatic pressure can, of course, be obtained by the illustrated water pressure generator or by introducing a high pressure gas into a closed container. When a cavity is present in the molded body 20 by being exposed to the high hydrostatic pressure, the cavity is crushed and disappears, but at this time, since a coating such as silicon rubber is applied, water or high pressure gas is applied. Does not enter the inside of the molded body 20 to cause a new defect. Pressurizer 24
The molded body 20 taken out from is sent to a peeling station 26 where the surface coating is peeled off. In the case of silicone rubber or the like, the coating can be easily peeled off by human power, but a device similar to a friction peeling device which is widely used for peeling of agricultural products can be advantageously employed. Next, the molded body 20 is heated to, for example, 300 ° C. in the low temperature heating furnace 28.
After being heated to a certain degree, organic substances such as a resin binder are decomposed, vaporized and removed, and then sent to the high temperature heating furnace 30.
Sintered in a high temperature, normal pressure or reduced pressure gas atmosphere of about 1700 to 1800 ° C, and taken out as a product. In the case of products that require particularly dimensional accuracy, finish processing may be performed by diamond grinding, or a conductive additive may be added to the raw material fine powder in advance to impart conductivity to the sintered body, and electric discharge machining may be performed. it can. In the fine ceramics product manufactured by the above method, the voids therein are crushed by a large hydrostatic pressure, so that sufficient strength can be secured.

As described above, the method for producing a fine ceramics according to the present invention includes a step of injecting a ceramic powder mixed with a resin binder to obtain a desired molded body, and forming the molded body by an easily separable coating such as silicon rubber. The step of coating, the step of hydrostatically pressurizing the molded body with the above coating at high pressure, the step of removing the coating film on the surface of the molded body that has been hydrostatically pressed, and heating the molded body from which the film has been removed at a low temperature. A step of removing the resin binder described above and a step of firing the molded body from which the resin binder has been removed under normal pressure. It is extremely beneficial because it can be mass-produced at low cost.

[Brief description of drawings]

 The accompanying drawings are process diagrams showing the outline of the method of the present invention. 16 …… Injection molding machine, 22 …… Coating station 18 …… Mold, 24 …… Hydraulic pressure press 20 …… Molded body, 28 …… Heating furnace

Claims (1)

[Claims] 1. A step of injection-molding a ceramic powder mixed with a resin binder to obtain a desired molded body, a step of coating the molded body with an easily separable coating such as silicon rubber, and a molding provided with the coating. A step of hydrostatically pressing the body under high pressure, a step of removing the coating film on the surface of the molded body that has been hydrostatically pressed, a step of heating the molded body from which the coating film has been removed at a low temperature to remove the resin binder, and a resin And a step of firing the molded body from which the binder has been removed under normal pressure.