JPH08259337A - Setter for baking and its production - Google Patents

Abstract

PURPOSE: To obtain a setter for baking excellent in spalling resistance. CONSTITUTION: Three to fifteen wt.% of a molten raw material whose chemical composition is composed of 30-70wt.% Al2 O3 and 70-30wt.% ZrO2 and whose mineral phase comprises corundum and monoclinic zirconia and whose particle size is 0.1-1mm is kneaded with 85-97wt.% of an alumina raw material and the kneaded material is formed and baked to produce the objective setter whose whole chemical composition comprises a high-alumina-based refractory composed of 90-98wt.% Al2 O3 , 2-10wt.% ZrO2 and <=1wt.% other component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high spalling-resistant setter used for firing electronic ceramics such as ferrite and dielectrics, and a method for producing the same.

[0002]

2. Description of the Related Art When firing ferrite or some dielectrics, a setter which does not react with these materials to be fired must be used. Therefore, conventionally, Al ₂ O ₃ 9
Alumina-based setter of 9% or more, or zirconia-based setter stabilized with CaO or the like was used.

[0003]

However, the alumina-based setter has a drawback that it has a high coefficient of thermal expansion and is poor in spalling resistance. For this reason, the alumina-based setter could not be made larger than a certain extent. Normally,
The limit was about 150 mm × 150 mm × 5 mm.

When firing soft ferrite in a pusher furnace, a setter is placed on a shelf plate for heat treatment. The size of the shelf board is generally 300 mm x 300
It is about mm × 10 mm. Therefore, normally, four alumina setters having the above-described dimensions were placed on one shelf plate for firing, but the firing target could not be loaded at the boundary between the setter and the setter, and the loading efficiency was poor. .

Further, even in the alumina-based setter having the above-mentioned size, depending on the use conditions such as the firing temperature, the shape and the weight of the article to be fired, cracks may occur due to thermal shock in the initial stage, and the setter may become unusable. It was This was a big negative cost.

[0006] On the other hand, there has been proposed a method of preventing the generation of initial cracks by adding fine powder of zirconia to an alumina raw material.

However, when the zirconia powder was added, the strength of the zirconia was reduced due to the residual expansion of the zirconia, and a sufficient service life could not be obtained.

In view of the above problems of the prior art, the present invention provides a firing setter suitable for firing electronic ceramics such as ferrite and dielectric, and excellent in spalling resistance, and a method for producing the same. Is intended.

[0009]

In the first invention of the present application, the chemical composition is 30 to 70% by weight of Al ₂ O ₃ and ZrO ₂ 70 to ₃ % by weight.
0% by weight, the main mineral phase is corundum and monoclinic zirconia, and the kneading is performed with 3 to 15% by weight of a molten raw material having a particle size of 0.1 to 1 mm and 85 to 97% by weight of an alumina raw material, By molding and firing this, the overall chemical composition is Al ₂ O ₃ 90-98 wt%, ZrO _{2 2-}
The gist is a method for producing a firing setter, which comprises producing a firing setter made of a high-alumina refractory material containing 10% by weight and 1% by weight of other components.

In the second invention of the present application, the chemical composition is Al ₂ O ₃ 3.
0 to 70% by weight, ZrO ₂ 70 to 30% by weight,
The main mineral phase consists of corundum and monoclinic zirconia,
3-15% by weight of molten raw material having a particle size of 0.1-1 mm
And 85 to 97% by weight of alumina raw material, and the overall chemical composition is Al ₂ O ₃ 90 to 98% by weight, Z
A high-alumina refractory material having rO _{2 of 2 to} 10% by weight and other components of 1% by weight or less, characterized in that microscracks are formed inside or around particles constituting the refractory material. I am trying.

[0011]

The chemical composition used in the present invention is Al ₂ O ₃ 30
70 wt% and melting the raw material consisting of ZrO ₂ 70 to 30% by weight, monoclinic zirconia corundum grain boundaries and has a tissue as dispersed.

Monoclinic zirconia expands and contracts abnormally at around 1000 ° C. Therefore, it is desirable to positively generate a large number of microcracks inside or around the particles when the molten raw material is procured or when the molten raw material is used as an aggregate and fired.

By positively utilizing the microcracks, the spalling resistance of the high-alumina firing setter can be greatly improved.

Further, according to the present invention, Al ₂ O ₃ and Zr
Since the components other than O ₂ are 1% by weight or less, the object to be fired and the setter do not react with each other, and therefore the characteristics of the object to be fired are not impaired.

[0015]

The preferred embodiments of the present invention will be described in detail below.

In the method for producing a firing setter of the present invention,
The chemical composition is 30 to 70% by weight of Al ₂ O ₃ and ZrO ₂ 7.
0 to 30% by weight, the main mineral phase is corundum and monoclinic zirconia, and 3 to 15% by weight of molten raw material having a particle size of 0.1 to 1 mm, and 85 to 97% by weight of alumina.
Is used as a raw material. This raw material is kneaded, molded and fired to give an overall chemical composition of Al ₂ O _{3 of} 90 to 98% by weight,
A sintering setter made of a high alumina refractory containing _{2 to} 10% by weight of ZrO _{2 and} 1% by weight or less of other components is obtained.

As the alumina raw material, fused alumina and / or sintered alumina is used. It is desirable to set the grain size to about 1 mm or less. The reason for limiting the grain size is that if the maximum grain size is 1 mm or more, the surface of the setter is rough and the burned material is easily scratched.

Regarding the difference between the case of using the fused alumina and the case of using the sintered alumina, the reactivity with the material to be fired differs depending on the existence form of impurities in the alumina crystal grain boundaries. Is not particularly affected.

A large number of microcracks are positively generated in advance inside or around the particles forming the molten raw material, or inside or around the particles forming the refractory when firing the high alumina refractory. It is desirable to actively generate a large number of microcracks. By increasing the number of microcracks in this way, spalling resistance can be significantly improved.

3% by weight of the molten raw material having the above chemical composition
If it is less than the above range, the spalling resistance cannot be sufficiently improved. When the amount of the molten raw material exceeds 15% by weight, the residual expansion of the monoclinic zirconia in the molten raw material lowers the strength of the setter as the number of times of use increases, and the possibility of cracking increases.

When the particle size of the molten raw material is less than 0.1 mm, the monoclinic zirconia in the molten raw material is likely to separate, and like the case of adding fine zirconia powder, the residual expansion of the zirconia causes the strength to increase with the number of times of use. As a result, the number of cycles (lifespan) becomes insufficient, and sufficient service life (life) cannot be obtained.

The content of other components contained in the high alumina refractory material constituting the firing setter is set to 1% by weight or less so that the other components do not react with the material to be fired and the characteristics of the material to be fired are not impaired. Is. It is desirable that SiO ₂ is not contained as another component. This is because SiO ₂ easily reacts with the material to be fired.

The firing setter of the present invention can be manufactured by the above manufacturing method, and is characterized in that a large number of microcracks are present inside or around the particles constituting the high alumina refractory.

FIG. 1 is an electron micrograph showing the particle structure of the firing setter of the present invention. As indicated by the arrow,
The presence of some microcracks is noted.

By the above method, Examples 1 to 3 of the fired setter were manufactured. In addition, Comparative Examples 1 to 7 were also manufactured, and the physical properties of Examples and Comparative Examples were compared.

Regarding the chemical composition of the molten raw material, Example 1
The chemical composition is 70% by weight of Al ₂ O ₃ and ZrO ₂ 3
A molten raw material consisting of 0% by weight was used. Examples 2, 4, 5
Is a molten raw material containing 50% by weight of Al ₂ O _{3 and} 50% by weight of ZrO _2, and in Example 3, 30% by weight of Al ₂ O ₃ and ZrO.
₂ 70% by weight of molten raw material was used.

On the other hand, in Comparative Example 3, the chemical composition is Al ₂ O ₃
A molten raw material composed of 80% by weight and 20% by weight of ZrO ₂ was used, and in Comparative Example 4, 10% by weight of Al ₂ O ₃ and ZrO ₂ were used.
90% by weight of molten raw material was used. As Comparative Example 1, a conventional alumina-based setter was used. In addition, Comparative Example 2
Monoclinic ZrO ₂ of 45 μm or less was used so that the same ZrO ₂ as in Example 2 was obtained.

Regarding the particle size and ratio of the molten raw material, in Examples 1 to 3 and Comparative Examples 3 to 4, 8% by weight of the molten raw material having a particle size of 0.2 to 0.5 mm was added. In Comparative Example 5, 8% by weight of the molten raw material of Example 2 having a particle size of 0.1 mm or less was added. In Examples 4 and 5, and Comparative Examples 6 and 7, the same molten raw material as in Example 2 was used, and the addition ratio was 3, respectively.
It was set to 15, 2, 20% by weight.

The particle size of the alumina raw material is 0.5 mm.
The following fused alumina and alumina fine powder obtained by the Bayer method were used and combined so that the overall particle size distribution was the same in all Examples and all Comparative Examples.

An aqueous solution of PVA as a binder was added to the above-mentioned raw materials (see Tables 1 and 2 for details) and kneaded with a mixer. After that, press the machine, 150m
It was molded into a setter shape of m × 150 mm × 5 mm, the molded body was dried, and fired at 1600 ° C. to manufacture a firing setter made of an alumina refractory material.

The spalling resistance of the obtained firing setter was examined as follows. That is, 300 mm x
A sample is placed in the center of a 300 mm x 10 mm shelf board, 30 mm x 30 mm x 10 mm ferrite is placed on it, and the shelf board is inserted into an electric furnace maintained at a set temperature.
After holding for 0 minutes, it was taken out and returned to room temperature. The set temperature was gradually increased from a low temperature, and the temperature at which cracks occurred was examined.

The results are shown in Tables 1 and 2.

[0033]

[Table 1]

[0034]

[Table 2] Further, these firing setters were actually used for firing flyback ferrite. The results are also shown in Tables 1 and 2.

As is clear from Tables 1 and 2, in Examples 1 to 5, it was confirmed that the spalling resistance was high, and the same raw material ratio was 300 mm × 300 mm ×.
When an attempt was made to produce a setter for firing of 8 mm, when the same raw material as in Comparative Examples 1, 3 and 6 was used, cracks were generated during firing and the setter was unusable.

[0036]

According to the present invention, a firing setter having excellent spalling resistance can be manufactured.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a particle structure in an example of a firing setter of the present invention.

Claims (5)

[Claims] 1. A chemical composition of Al ₂ O _{3 is} 30 to 70% by weight.
And ZrO ₂ 70 to 30 wt%, the main mineral phase is corundum and monoclinic zirconia, and the particle size is 0.1.
By melting 3 to 15% by weight of the molten raw material having a size of 1 mm and 85 to 97% by weight of the alumina raw material, and molding and firing the mixture, the overall chemical composition is Al ₂ O ₃ 90 to 98.
A method for producing a firing setter, which comprises producing a firing setter made of a high alumina refractory containing 1 wt% or less of ZrO _{2 and} 10 wt% of ZrO ₂ . 2. The method for producing a setter for firing according to claim 1, wherein at least one of fused alumina and sintered alumina is used as the alumina raw material. 3. The method for producing a firing setter according to claim 1, wherein microcracks are generated inside or around the particles constituting the molten raw material. 4. The method for manufacturing a firing setter according to claim 1, wherein microcracks are generated inside or around the particles constituting the refractory when the high-alumina refractory is fired. 5. A chemical composition of 30 to 70% by weight of Al ₂ O _{3 and} 70 to 30% by weight of ZrO ₂ , a main mineral phase of corundum and monoclinic zirconia, and a grain size of 0.1.
It is formed by using 3 to 15% by weight of a molten raw material having a diameter of ˜1 mm and 85 to 97% by weight of an alumina raw material, and has an overall chemical composition of 90 to 98% by weight of Al ₂ O ₃ , ZrO ₂ 2 to 10% by weight, and A high alumina refractory having 1% by weight or less of other components, wherein microcracks are formed inside or around the particles constituting the refractory, and a sintering setter.