JP2828517B2 - Ceramic firing container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sintering vessel for heating a raw material powder to a high temperature to sinter the powder into ceramic fine powder.

[0002]

2. Description of the Related Art Ceramic fine powder is disclosed in
As disclosed in JP-A-58806 and JP-A-62-100404, the raw material powder is heated to 1200 ° C to 20 ° C in a predetermined atmosphere such as non-oxidizing.
It is heated to a high temperature of 00 ° C., refined, and simultaneously fired into ceramic fine powder. In this case, a graphite crucible is usually used as a firing container. As the conventional firing vessel (hereinafter simply referred to as a vessel), an outer diameter of about 300 mm is frequently used. As shown in FIG. The whole is covered with the muffle 4 in the muffle furnace 3 and heated by the electrode 5 through the muffle 4. In addition, 6 is a hearth and 7 is a duct for exhaust gas.

[0003]

However, since the containers are stacked in a block shape, the volume efficiency in the muffle is low, and despite the small diameter of the container, the vicinity of the inner surface of the container and the central portion are reduced. , A temperature difference occurs, and the temperature rise curve has a large delay at the center of the container 1 as shown in FIG. In this figure, there is not much difference from the set temperature rise curve near the bottom and the side wall of the container 1 as shown by. Inevitably, the holding time at the set temperature must be extended accordingly.

[0004] Therefore, the crystal particle diameter varies at the center of the container, and the amount of heating power used increases, which is a problem. This tendency is naturally promoted as the diameter of the container increases. The present invention has been made in order to solve the above-described problems in the conventional ceramic firing container, all the filled raw material powder is almost uniformly heated,
It is an object to provide a container that can be heated.

[0005]

According to the present invention, there is provided a vertical container having an outer cylinder, wherein an inner cylinder concentric with at least one of the outer cylinders and / or a heat transfer cylinder is erected at the center of the vessel. Furthermore the size of each part to the outer diameter D ₀ of the container is set to be in the range of the following conditions to solve the problems in the conventional ceramic firing vessel above.

[0006] The container bottom thickness h = 0.05D ₀ ~0.1D ₀ most of the inner cylinder in the inside of the outer diameter _{D 1 = 0.2 D 0 ~0.5 D} 0 outer tube thickness t ₀ = 0.02D ₀ ~0.05D the thickness of ₀ inner cylinder t ₁ = 0.02D ₀ ~0.05D ₀ heat transfer cylinder of diameter d = 0.05 d ₀ ~ 0.1 d ₀

[0007]

The container according to the present invention comprises at least one inner cylinder and / or a heat transfer cylinder standing at the center of the container in a conventional vertical container, and transfers the heat applied to the bottom of the container to these inner cylinders. By transmitting the powder to the raw material powder in the container via the column, it was possible to heat and raise the temperature of the ceramic powder in the whole container almost uniformly.

First, various types of containers were experimentally manufactured, and it was found that the container having the above configuration was most effective. However, the heat transfer cylinder erected at the center of the container may be cylindrical, but in general, a high-temperature container is made by turning from a graphite material, so it is difficult to turn a cylinder with an inner diameter that is too small, In order to fill the raw material powder, it is advantageous that the inner volume of the container is as large as possible.

The above-mentioned dimensions of each part of the container according to the present invention are determined in order to uniformly heat and raise the temperature of the raw material powder and to prevent cracking due to thermal stress due to repeated heating and cooling. It is a thing. Based on these findings, three types of containers as shown in FIG. 1 were prototyped. A corresponds to a conventional container, B and C are containers according to the present invention, B is only an inner cylinder, and C is an upright cylinder and a heat transfer cylinder. The dimensions of these containers are as shown in Table 1. The containers were filled with the raw material powder, and the atmosphere temperature in the muffle was increased from 970 ° C to 1100 ° C.
C. and heated for about 220 minutes. The temperature difference between the powder temperature near the container side and the powder temperature at the center at that time-
Are also shown in Table 1.

[0010]

[Table 1]

As can be seen from the table, in the case of A corresponding to a conventional container, a considerable temperature difference occurs, and B in which only the inner cylinder is erected.
However, there is a considerable effect, and there is almost no temperature difference in C where the inner cylinder and the heat transfer cylinder are erected. It was also found that a small-diameter vessel was effective even if only a heat transfer cylinder was erected at the center. Further, the temperature rise curve of the powder was examined for the container C according to the present invention. At this time, the atmosphere temperature in the muffle was 1000 ° C., and the temperature of the powder became about 950 ° C. after about 230 minutes, as shown in FIG.

The dimensions of the container will be described in more detail. The dimensions of each part are related to each other in terms of strength. In particular, the outer diameter D _{0 of the} container and the bottom thickness h, the bottom thickness h and the outer cylinder In addition, the thicknesses t ₀ and t ₁ of the inner cylinder have a large relationship. On the other hand, the inner volume of the container should be as large as possible, as described above. The above conditions are determined in consideration of the heating state of the powder confirmed in the experiment.

The height H of the container should be appropriately determined according to the composition and amount of the gas generated in the firing reaction depending on the components of the raw material to be treated. For example, in the case of a boron nitride ceramic, If the height H exceeds 300 mm, it is difficult to escape the generated gas, and the size of the crystal grains may vary, so it is preferable to set the height to 300 mm or less.

[0014]

FIG. 3 is an explanatory view of one embodiment of the present invention, and FIG. 4 is an example in which a ceramic powder is fired using this container. In FIG. 3, a container 10 is a vertical container including an outer cylinder 11 and a bottom portion 12.
And a heat transfer cylinder 14 is provided upright at the center thereof. Further, the centering notch 15 provided to match the center of the muffle with the center of the container, and the stacking of the containers with the center of the container aligned as shown in FIG. Steps provided around the entire lower edge
16 and gas vent openings 17 provided at four places on the upper edge. The step 16 and the opening 17 are not necessary if they are not stacked and used. 18 is a notch for handling.

The dimensional condition of this container is that its outer diameter D
Against _0, the thickness t of the outer diameter _{D 1 = 0.2 D 0 ~0.5 D} 0 outer tube 11 of the inner cylinder 13 in the most thickness h = 0.05 D ₀ to 0.1 D ₀ interior of the container bottom 12 ₀ = 0.02 it is a matter of course you have a diameter d = 0.05D ₀ ~ 0.1D ₀ thickness t ₁ = 0.02D _{0 ~0.05D 0} heat transfer cylinder 14 of the D ₀ ~0.05D ₀ inner cylinder 13.

Here, the number of inner cylinders is not limited to one, and a plurality of inner cylinders may be provided at appropriate positions as needed.
Also in that case, the outer diameter of the innermost inner cylinder must be within the above range, and the thickness of all the inner cylinders must be within the above range. It is also conceivable to use all or some of the inner cylinders as heat conductors such as cylinders in place of the inner cylinder, but most of the containers of the present invention are made by turning from a graphite material. However, the configuration is limited to a configuration in which all the shapes are arranged concentrically.

FIG. 4 shows a state in which the containers 10 of the present invention are stacked in three stages with their axes aligned so as to be reacted. 4 is a muffle, 6 is a hearth, and 6 'is a cradle for the container 10. Reference numeral 5 denotes a heating element such as an electrode. The boron nitride-based raw material powder 2 was heated to about 2000 ° C. through a muffle 4 and a container 10 in a muffle furnace (not shown), and subjected to a reaction treatment by holding the powder for about 120 minutes. . The dimensions of the container 10 used in this case are shown in Table 1C, and the processing results are shown in Table 2 in comparison with the conventional technology.

[0018]

[Table 2]

As shown in Table 2, it can be seen that the present invention has less variation in crystal particle diameter and improved yield.

[0020]

When the ceramic firing vessel according to the present invention is used, the heating and heating can be performed uniformly throughout the entire vessel, so that the variation in the crystal particle diameter of the ceramic fine powder is reduced and the yield is improved. In addition to this, there is an advantage that power consumption can be reduced because the entire processing time can be shortened, processing can be performed in an upright state, and processing efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the operation of the present invention.

FIG. 2 is an explanatory diagram showing an example of a temperature rise curve of the ceramic firing container according to the present invention.

3 (a) is a sectional view, and FIG. 3 (a) is a plan view of an embodiment of the ceramic firing container according to the present invention.

FIG. 4 is an explanatory view showing an example of a case of performing a firing treatment using the ceramic firing container of the present invention.

FIG. 5 is an explanatory view in the case of performing a baking treatment using a conventional baking container.

FIG. 6 is an explanatory diagram of a temperature rise curve of each part in a container in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic firing container 2 Raw material powder 3 Muffle furnace 4 Muffle 5 Electrode 6 Hearth 7 Duct 10 Ceramic firing container 11 Outer cylinder 12 Container bottom 13 Inner cylinder 14 Heat transfer cylinder 15 Cut 16 Stepped part 17 Opening 18 Cut

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Toriko 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Kawasaki Steel Corporation Mizushima Works (56) References JP-A-2-172858 (JP, A) JP-A-1-230409 (JP, A) JP-A-3-67899 (JP, U) Japanese Utility Model Sho 62-83837 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F27D 3/00-3/18 C04B 35/64

Claims (2)

(57) [Claims] 1. A container for firing powder ceramic, comprising:
A ceramic firing container comprising: a vertical container having an outer cylinder; an inner cylinder concentric with at least one of the outer cylinders; and / or a heat transfer cylinder standing upright at the center of the vessel. 2. A container according to claim 1 ceramic firing vessel according to the dimensions of each part to the outer diameter D ₀ is characterized in that it is a range of the following conditions. Container bottom portion having a thickness of h = 0.05 D ₀ outside diameter of ～0.1D ₀ inner cylinder which innermost _{D 1 = 0.2 D 0 ~0.5 D} 0 of the outer tube thickness t ₀ = 0.02D ₀ ~0.05D ₀ inner cylinder thickness t ₁ = 0.02D ₀ ~0.05D ₀ heat transfer cylinder with a diameter d = 0.05D ₀ ~ 0.1D ₀