JPS5918168A - Method of burning ceramic moldings - 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 The present invention relates to a method for firing a ceramic molded body in which the shrinkage rate of each part of the ceramic molded body during sintering is made substantially uniform.

Conventionally, a ceramic powder compact is sintered by placing the compact 2 on a flat plate 11 as shown in FIG.
The molded body 2 was set inside the container.

However, in the conventional firing method, the contraction rate of each part of the molded body 2 that is pressed during sintering varies, and as a result, undesirable deformation may occur in the product. This is because when the molded body 2 contracts during sintering, the molded body 2 and the plays 1 to 11 or the container 12 on which the molded body 2 is placed are
Frictional resistance or sticking occurs between the bottom surface of the
This is due to the fact that the portion of the molded body 2 is pulled toward the play 11 or the bottom surface of the container 12, preventing the portion from shrinking.

The present invention was devised in view of such drawbacks of the conventional sintering method. The purpose of the present invention is to provide a firing method that allows a product with good quality to be obtained.

That is, the firing method of the present invention is similar to the conventional firing method in which the ceramic powder compact to be sintered is placed on a base such as a flat plate or inside a firing container, and then heated to a predetermined temperature. As an improvement, a thin layer of ceramic powder is provided between the molded body and a base such as the plate or the bottom of the firing container, and then sintered.

Here, the ceramic powder layer must be made of a material that does not react with or sinter with the compact at the sintering temperature. Furthermore, the material must have lubricity at the sintering temperature.

Such a substance is a substance forming the relamic molded body,
It is determined by the relationship with the sintering atmosphere. For example, the atmosphere is nitrogen (N2), and the molded body is made of silicon nitride (Si3).
N4), silicon carbide (SiC), etc., boron nitride is suitable as the ceramic powder layer.

13. According to experiments, the thickness of the ceramic powder layer is preferably about 0.2 to 2 ml11, and the particle size of the powder is preferably about 2 to 5 μm.

By interposing a thin layer of such ceramic powder between the molded body to be sintered and a base such as a plate or the bottom of a container on which the molded body is placed, the molded body and the base are Frictional resistance between the two is reduced, and sticking is also prevented. Therefore, the shrinkage rate of each part of the molded body during sintering becomes substantially uniform, and a sintered body with good dimensional accuracy can be obtained. In addition, since 1q of sintered bodies with good accuracy in one method are produced, the margin for finishing the sintered bodies can be reduced, which is efficient.

The present invention will be specifically described below with reference to illustrated embodiments.

FIRST EMBODIMENT On the bottom of a box-shaped baking container 12 as shown in FIG.
A layer 4 of boron nitride powder with a particle size of 2 to 5μ,
It was formed with a thickness Q of 3 mm. The formation of the boron nitride powder layer 4 is as follows: 1. Mixing the boron nitride powder with alcohol;
How to apply this using a sprayer.

2. A method of applying boron nitride powder to a core metal to a thickness of 0.3 to 5 mm and shaping it using a brush.

3. Method of molding using commercially available borosinitride spray.

The above three methods were used.

Next, a cylindrical silicon nitride compact 21 with an outer diameter of 901 and a height of 50 ml11 is placed on the boron nitride powder layer 4 thus formed as shown in FIG. It was sintered by heating at 1750° C. in an atmosphere for 4 hours.

After sintering, the shrinkage percentage of the molded body 21 was measured on the upper surface side A and the lower surface side B of the cylinder, and the shrinkage ratio was 19.3% on the upper surface side A and 19.2% on the lower surface side B.

On the other hand, when the boron nitride powder layer 4 is not used and the other conditions are the same, when sintering is performed by the conventional method, the percentage is 18.6% on the top side A and 19.3% on the bottom side B. %Met.

That is, when the boron nitride powder layer was used, the difference in shrinkage rate between each part of the compact 21 was extremely small. It should be noted that a difference in the formation conditions of the boron nitride powder layer was observed, and the difference in shrinkage rate could be reduced by any of the methods described in 12.3 above.

Second Embodiment As shown in FIG.
A layer of boron nitride (BN>4) was formed with a thickness Q of 3 mm. As in the first example, three formation methods were employed.

Next, the layer of boron nitride 4 (7) formed in this way
After placing a disc-shaped silicon nitride molded body 22 with a diameter of 110 mm and a thickness of 15 Illn on top, it was heated in a nitrogen atmosphere for 4 hours.
It was sintered by heating to 1750° C. for an hour.

After sintering, the shrinkage rates of each part of the molded body 22 were compared and found to be 18.6% on both the upper surface side A and the lower surface side B in FIG.

On the other hand, when the boron nitride layer 4 was sintered using the conventional method under the same f1 and other conditions, the shrinkage rate was as follows.
18.4% to the top side, bottom side BT in contact with the base:
It was 18.1%.

That is, by forming and sintering the boron nitride layer 4, it was possible to reduce the difference in shrinkage rate in each part compared to the conventional sintering method. Note that, similar to the first example, no difference was observed depending on the method of forming the boron nitride layer 4.

19. As is clear from the detailed description of the examples, according to the sintering method of the present invention, the shrinkage rate at each part of the a3 ceramic molded body can be made approximately uniform during sintering. I can do it. Therefore, a sintered body with good dimensional accuracy can be obtained, and deformation can also be prevented. Furthermore, since the dimensional accuracy is good, the machining allowance during grinding can be reduced, and the grinding time can be shortened. Moreover, as a result of being able to shorten the grinding time, it is possible to increase the number of products manufactured per grinding machine.

[Brief explanation of the drawing]

Figure 1 shows the conventional firing method in which the molded body is placed on a plate, Figure 2 shows the conventional firing method in which the molded body is set in a container, and Figure 3 shows the first method. FIG. 4 is a diagram showing the firing method of the second embodiment. 11... Plate 12... Container for firing 2... Molded body 4... Ceramic powder layer patent applicant 1 ~ Yota Jidosha Co., Ltd. agent patent attorney Hiroshi Okawa

Claims (1)

[Claims] (1> In a method for firing a ceramic molded body, in which the ceramic molded body is placed on a base and then heated, there is a gap between the ceramic molded body and the base under the sintering temperature and atmosphere. . A firing method characterized in that a layer of ceramic powder that does not react with or sinter with the ceramic compact and has lubricating properties is interposed therebetween.