JPS5820776A - Zirconia-impregnated alumina refractories - 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] Traditionally used for firing capacitors, piezoelectric elements, etc.

For use in alumina or mullite boards, saggers, and other utensil bricks to prevent reactions with the objects to be treated.

Corrosion-resistant zirconia-based or magnesia-based setter tiles are stacked on the tool bricks, and the workpiece is placed on the setter tiles and fired, but the present invention does not use the corrosion-resistant setter tiles.

The object to be processed is placed directly on the lower plate or sagger pot and fired.
Man 6 + resistance + 1 / thing ~ It is the main thing to do to oneself.

The demand for barium titanate-based or perovskite-based ceramics as electrical circuit components such as capacitors and piezoelectric elements has increased significantly with the development of consumer and industrial equipment. In addition to mass production, there are also strong demands for improvements in labor saving, resource saving, energy saving, etc. in the process, and there are particularly high expectations for improvements in the firing method, as it has a large impact on its effectiveness.
.

For example, there is a strong demand for making bricks for firing tools thinner and with a much smaller heat capacity.

In response to such demands, the present invention improves the corrosion resistance of the lower plate and sagger, and eliminates the use of the upper setter tile, thereby saving labor, resources, and energy, which can be mass-produced. This is said to be the most effective improvement method for reducing costs.

Conventionally, when firing barium titanate-based or perovskite-based ceramics, corrosion-resistant zirconia-based or A common method is to stack magnesia-based setter tiles, place the workpiece on top of them, and then fire. However, this zirconia and magnesia setter tile has a high specific gravity and a large heat capacity due to 2 weights.

This has the disadvantage that spall cracks occur frequently due to thermal stress, and the wear and tear cannot be ignored. Therefore, in order to impart the corrosion resistance of the setter tile to the alumina refractories of the lower plate, sagger, etc., a relatively thin layer of zirconia with an uneven contact surface is attached to the upper surface of the plate or sagger during molding. A layer was formed, and the object to be treated was directly placed on the formed surface and fired, but the zirconia layer peeled off early due to the difference in expansion and good results could not be obtained.

The object of the present invention is to solve the above-mentioned early peeling problem.

The open pores of the alumina refractory structure are impregnated with a zirconia solution and fired to form zirconia crystals within the pores, or after impregnation, a suspension of zirconia fine powder is sprayed onto one surface, or The object of the present invention is to provide a refractory that is completely free from peeling and has high corrosion resistance by coating and firing to form a thin zirconia film on the surface.

That is, the present invention provides a manufacturing process for alumina-based refractories in order to form zirconia crystals in the open pores of alumina-based or mullite-based refractories, or to further form a strong thin layer of zirconia on the surface. Among them, semi-finished products with high open porosity, that is, dry products.

A semi-finished product in an unglazed state or a product in an almost fired state is immersed in a zirconia solution such as an aqueous solution of zirconium chloride, zirconyl acetate, or an active inorganic polymer containing zirconium as a main component, or zirconia fine particles that cannot be felt with the tip of a finger. It is impregnated by immersion in a colloid solution in the atmosphere or in a vacuum chamber.

It is also more effective to repeat the above-mentioned impregnation process on the dried product after impregnation. Furthermore, in order to change the amount of zirconia fine powder mixed on the surface of the tool brick depending on the degree of reaction with the object to be treated, a suspension with the amount of fine powder adjusted in advance is applied to the surface of the tool brick after impregnation. , sprayed or applied and then in the atmosphere.
1200-1500℃ where M tool bricks undergo some firing shrinkage
The characteristics of the present invention include zirconia crystals grown in the open pores by firing at a temperature of 1, and a thin layer of zirconia on the surface firmly bonded to the crystals.

As mentioned above, the present invention brings about good results that lead to mass production in addition to the effects of saving money, saving resources, and saving energy. However, in order to obtain even more efficient effects,

The amount of zirconia impregnated or further formed on the surface.

In other words, since the degree of weight increase after firing affects the corrosion resistance effect, it is suitable for treated materials with two strong reactivity.

Refractories whose open pores are sufficiently impregnated with zirconia and a thin film of zirconia formed on the surface can be used, and refractories with a small amount of impregnation can be used for weakly reactive materials, but corrosion-resistant Since there is a limit to economic efficiency, we conducted an experiment on the weight increase of zirconia for the open pores of the refractory substrate and obtained the following values.

In other words, in general, for alumina refractories with an open porosity of 10 to 20%, those with a weight increase of less than 2% by Silfea are treated with a reaction of less than 1, but are eroded and have little effect.
% or more in weight tends to be superior in corrosion resistance but inferior in spalling resistance.

In addition, the cost was increased due to repeated impregnation and coating, resulting in poor economic efficiency. That is, it has been found that the effective weight increase of zirconia according to the present invention is in the range of 2 to 13%, which is most effective both in terms of characteristics and economically.

Next, examples of the present invention will be described.

Example 1 Using a high alumina raw material containing 75% alumina and 25% silica, a plate shape with 9 dimensions of 200mm in length and width and a thickness of 15mm was molded by pumping, and after drying, it ℃
The weight obtained by bisque firing is 1.351j, and the open porosity is 2.
1% semi-finished board.

The surface of the impregnated plate obtained by impregnating it in a solution of zirconyl acetate (Zr (h concentration 15%) for 15 minutes in a vacuum (750 m of mercury) and air drying for 16 hours was separately soaked in a solution of zirconyl acetate with a purity of 99. A suspension obtained by mixing and stirring 20% of zirconia fine powder with a particle size of 325F at 5% was sprayed to form a thin film, and after air drying for 5 hours, it was baked at 1450°C in air for 5 hours to increase the weight by 9. A zirconia-impregnated alumina refractory having a thin film of zirconia particles of 50 μm fixed to the surface was obtained.

When the barium titanate dielectric material to be treated was fired without a setter tile, there was no erosion or peeling phenomenon on the contact surface of the plate, and compared to the 50 times that the conventional setter was used, the product of the present invention also fired the same 50 times. − times of practical use were obtained.

Example 2 Using a high alumina raw material with an alumina content of 80% and a silica content of 20%, a sagger with external dimensions of 200 mm in length and width, 50 mm in height, and a wall thickness of 13 mm on each side was made. The weight obtained by press molding using the usual method and firing at 1200℃ is 1.9
At 21j, a fired sagger with an open porosity of 18% was vacuum impregnated in a solution of zirconyl ammonium carbonate (Zr (h concentration 20%) under the same conditions as in Example 1, and after drying,
It was refired at 450°C to obtain a sagger with a zirconia weight increase of 5%. As in Example 1, a weakly reactive barium titanate-based material was directly placed and fired, but the conventional sagger was
2 quality bedding sand was used by spreading it, but the product of the present invention did not use it and the same effect was obtained fc. The effect of this example is that it is possible to reduce the number of man-hours required for loading the material to be processed into the sagger pot by 7%.9. In addition to the corrosion resistance, the sagger itself has a 2-3% reduction in apparent porosity, a 10% increase in strength, and a 20-50% increase in lifespan due to cracks.

As mentioned above, the zirconia-impregnated alumina refractory according to the present invention has improved corrosion resistance, which eliminates the need for conventionally used setter tiles, and also leads to labor savings, resource savings, energy savings, and mass production. It is said to be a groundbreaking invention that met the demands of the world.

Patent applicant: Tokai Konetsu Kogyo Co., Ltd.

Claims (1)

[Claims] Impregnating with a zirconia-containing solution or a colloidal solution of zirconia fine powder, or spraying or coating the surface with a suspension of zirconia fine powder after impregnation, followed by drying and firing. The weight of zirconia increases later. A zirconia-impregnated alumina refractory characterized by 2-13%.