JP3142663B2 - Zirconia kiln tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zirconia refractory, and more particularly to a zirconia kiln tool which is stable against heat history such as heating and cooling and can be used repeatedly.

[0002]

2. Description of the Related Art When a material to be fired is fired while passing through a furnace such as a pusher furnace, the material to be fired is placed on a refractory setter or sagger. It moves to pass through and is fired. In general, as a kiln tool used in this way, a zirconia-based fired refractory is known. Such a refractory is, for example, 70 to 95% by weight of a zirconia coarse particle raw material, 30 to 95% by weight.
A mixture comprising 3% by weight of a zirconia fine powder raw material, a small amount of a binder and water is kneaded by a method called fret kneading to obtain a kneaded material. It is produced by firing in the surrounding atmosphere.

In such a setter, conventionally, a zirconia-based raw material is stabilized by using one of stabilizers such as CaO, Y ₂ O ₃ , and MgO alone, and is used as a raw material. By manipulating the conversion ratio, the particle size of the raw material, etc., the reaction resistance to the object to be fired and the characteristics of the setter itself have been improved.

[0004]

However, such conventional kiln tools such as setters are not stable against heat history due to heating and cooling. That is, by using such a setter and firing an electronic component such as a ceramic capacitor at an appropriate firing temperature of about 1100 to 1400 ° C. and then cooling, the residual expansion coefficient of the setter is a positive value. Therefore, there has been a problem that the material gradually expands, and when the expansion ratio exceeds 2%, cracks are generated, and the setter is eventually broken. Here, the “residual expansion rate”
When the setter is heated to the maximum temperature and expands, and then cooled and contracts, it refers to the degree of expansion remaining in the setter after cooling. Therefore, when the residual expansion rate is positive, it means that the setter has expanded before heating (when heating a plurality of times, before immediately before heating). On the other hand, when the residual expansion coefficient is negative, it means that the resin has contracted before heating.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to stabilize heat history such as heating and cooling and to improve durability against repeated use. It is to provide an excellent zirconia kiln tool.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on various materials and firing methods and the like. As a result, a compact containing zirconia powder was reduced to a temperature below a normal sintering temperature. By firing in a low temperature region of the above, a refractory material having a negative residual expansion coefficient was obtained, and it was found that the above problem could be solved by using this refractory material as a kiln tool, thereby completing the present invention. Therefore, the zirconia-based kiln tool of the present invention is a kiln tool obtained by firing zirconia powder, and is characterized in that the residual expansion coefficient is negative.

[0007]

The kiln tool of the present invention has a negative residual expansion coefficient. Therefore, the thermal history due to repeated heating and cooling tends to shrink rather than expand in the initial stage, and it takes an extremely long time to reach an expansion rate at which cracks and the like occur and breakage starts. It is stable against such heat history and has excellent durability against repeated use.

Next, the raw material powder of the kiln tool of the present invention will be described. As the raw material powder for the kiln tool of the present invention, it is preferable to use zirconia powder stabilized by one or more compounds. . Examples of these compounds include calcium oxide, magnesium oxide and yttrium oxide, and calcium oxide and yttrium oxide are preferred. Further, such zirconia is not limited to whether it is completely stabilized zirconia or partially stabilized zirconia. The particle size of the raw material powder is not particularly limited, but usually, a powder having a particle size of 500 μm or less is used, and the powder is separated into coarse particles, medium particles, and fine particles. It is preferable to use a mixture.

Next, a method for manufacturing a kiln tool of the present invention will be described. The kiln tool of the present invention fills a molding die with the above raw material powder, pressurizes it at a pressure of about 0.6 to 1.0 ton / cm ^{2 to} give a predetermined shape, Firing in a low temperature range below the sintering temperature (hereinafter "low temperature firing")
That. ). This low-temperature firing
The temperature at which conventional zirconia refractories are fired is about 1
A temperature slightly lower than 600 ° C., ie about 1200 to 1500
It can be carried out by heat treatment at about 0.1 to 10 hours.

[0010]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (Examples 1 to 9) As raw material powders, CaO-stabilized zirconia was used, and the respective raw material powders were mixed at particle sizes and compounding ratios as shown in Table 1. This mixture is put in a mold at 1 ton / cm ²
88mm x 88mm x thickness 3mm
Was formed. Each of the obtained molded bodies was fired (low-temperature firing) at the temperature shown in Table 1 for 6 hours to obtain a zirconia refractory setter. (Comparative Examples 1 to 3) The same operation as in Examples 1 to 9 was performed except that the raw material powders were mixed at the particle sizes and compounding ratios shown in Table 1 and fired at the firing temperatures shown in Table 1.

(Evaluation of performance) (Number of times of firing shrinkage) From each of the refractory setters obtained in the above Examples and Comparative Examples, 50 mm × 5 mm × thickness 3
mm test piece was cut out, and the obtained test piece was heated at 300 ° C /
The temperature was increased to 1150 ° C. or 1400 ° C. by heating at hr, and kept at this temperature for 10 minutes. Next, the test piece was gradually cooled to room temperature, and its dimensions were measured to determine whether it was contracted or expanded. This operation was repeated to measure the number of times contraction occurred before the test piece expanded, and the results are shown in Table 1.

(2% Residual Expansion Ratio Number)
The temperature was raised at 0 ° C./hr to 1150 ° C. or 1350 ° C., and kept at this temperature for 10 minutes. Next, the test piece was gradually cooled to room temperature, and its dimensions were measured. This operation was repeated, and the number of operations required for the test piece to have an expansion rate of 2% was measured. The results are shown in Table 1. (Normal Temperature Bending Strength) The test piece was subjected to a four-point bending strength test at room temperature, and the results are shown in Table 1.

[0013]

[Table 1]

As is clear from Table 1, the zirconia refractory setter of the present invention tends to shrink rather than expand when subjected to a heat treatment at about 1100 to 1400 ° C. required for firing electronic components. It can be seen that they have extremely excellent durability. In addition, the flexural strength of 50 kg / cm ² or more required for such a setter is satisfied.

[0015]

As described above, according to the present invention,
By firing the stabilized zirconia powder at low temperature,
Since a negative residual expansion coefficient is provided, a zirconia kiln tool that is stable against heat history such as heating and cooling and has excellent durability can be provided. The kiln tool of the present invention has a long product life due to its excellent durability,
Therefore, it is possible to contribute to a reduction in the manufacturing cost of the object to be fired.

Continuation of the front page (56) References JP-A-5-270911 (JP, A) JP-A-5-270910 (JP, A) JP-B-2-2823 (JP, B2) Patent 3006729 (JP, B2) ( 58) Field surveyed (Int. Cl. ⁷ , DB name) F27D 3/12 C04B 35/48 C04B 35/64

Claims (3)

(57) [Claims] 1. A kiln tool formed by molding and firing a zirconia powder, wherein the residual expansion coefficient is a negative value. 2. Forming a stabilized zirconia powder,
The zirconia kiln tool according to claim 1, wherein the zirconia kiln tool is fired at 1200 to 1500C. 3. The zirconia kiln tool according to claim 1, wherein the bending strength is 50 kg / cm ² or more.