JPS62241869A - Manufacture of zirconia base 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 [Industrial Application Field] This invention relates to a method for producing a zirconia refractory having high corrosion resistance, high spalling resistance, high strength, and high heat resistance.

[Prior art and its problems]

Zirconia has a very high melting point of 2700° C. and also has excellent corrosion resistance against molten metal, molten glass, molten slag, etc., so it is used as a raw material for refractories for high-temperature operations.

The crystal system of this zirconia changes from a monoclinic system to a tetragonal system at a temperature around 1200° C., and a large volume change occurs at this time. Therefore, as a conventional method to prevent the volume change accompanying the transition of this crystal system, monoclinic zirconia was
By adding O or at least one of Y and O and heat-treating the zirconia, part or all of the zirconia is made into a cubic crystal, so-called stabilization. The stabilized zirconia, which has become a cubic crystal in this way, has a temperature of 2,700 yen from room temperature.
There is no change in the crystal system up to the melting point of °C, and it is stable, so there is no destruction of the structure due to volume changes. Especially Y z O3
Zirconia stabilized with CaO has excellent heat resistance, corrosion resistance, and spalling resistance, but its use is limited because it is expensive, and zirconia stabilized with CaO is usually used.

However, in order to increase the degree of stabilization of this stabilized zirconia, it is necessary to use a large amount of stabilizer, and when a large amount of stabilizer is used in this way, the problem of volume change due to system transition is resolved. However, on the contrary, phenomena such as an increase in the coefficient of thermal expansion and an intensified reaction between the stabilizer and molten metal slag, molten slag, molten glass, etc. are observed, resulting in poor spalling resistance and corrosion resistance. This is not preferable because it causes a decrease in the properties of zirconia and impairs the original properties of zirconia.

In addition, in zirconia using Cab or MgO as a stabilizer, due to thermal history, the stabilizer inside the crystal is extracted to the outside of the crystal, resulting in so-called destabilization, which returns to monoclinic zirconia. Deterioration of corrosion resistance due to the reaction between the stabilizer and the aforementioned molten metal, molten glass, and molten slag, and the presence of impurities such as SiO□ in the slag further promote destabilization.

As mentioned above, there is a problem in that the stability and corrosion resistance of zirconia refractories are contradictory, and this has been an obstacle to the development of highly corrosion resistant zirconia refractories.

[Means for Solving the Problems] This invention was proposed in view of the above-mentioned conventional circumstances regarding zirconia refractories. The purpose is to obtain a zirconia refractory with excellent properties.

In order to achieve the above object, the present invention employs the following means. That is, 100 parts by weight of zirconia clinker containing 50% by weight or more and less than 95% by weight of electrofused bump light clinker, and 0.3 to 3 parts by weight of at least one sintering agent such as clay, alumina fine powder, phosphoric acid, etc. After kneading and shaping, it is fired at 1,600 to 1,900°C.

[Effect]

In this invention, it is necessary to use, as a refractory raw material, a zirconia clinker containing 50% by weight or more and less than 95% of fused paplite clinker, which undergoes transition but does not cause tissue destruction at a crystalline transition temperature of 1200°C. be. The electrofused paplite is preferably produced by a conventional electrofusion method, and its mineral composition is monoclinic zirconia alone.

In place of this electric fusion pap light, natural pap light and wet refining bump light are not preferred because they cause tissue destruction due to system transition at 1200°C.

If the content of the electrofused buff plyte clinker is reduced to some% or less, there will be no significant difference in corrosion resistance from conventional zirconia refractories, which is not preferable. On the other hand, when 95% by weight of fused Baddeleyte talinker is used, fluff is less likely to be formed due to sintering of other zirconia clinkers, which will be described later.
A sintering process using an ultra-high temperature of 4900°C or higher is required.

The particle size of the fused Paplite clinker may be adjusted as appropriate depending on the purpose, and the particle size is usually 3500 to 1000.
It is sufficient to use particles ranging from coarse particles of about .mu.m to fine particles of about 44 .mu.m or less.

The above zirconia clinker is used in addition to electric fusion pap light.
~15IIIOIle% MgO, or O~10so
Contains zirconia clinker stabilized with le% CaO. As the stabilized zirconia clinker, a wet refined zirconia clinker, a sintered zirconia clinker, or a fused zirconia clinker can be used. Here, if the stabilizer is MgO, 15mof6%, CaO
If it exceeds 10 sol e%, the stabilizer will be released outside the structure of the zirconia particles, impairing corrosion resistance, which is not preferable.

If the amount of sintering aids such as clay, fine alumina powder, phosphoric acid, phosphate, etc. is less than 0.3% by weight, the sintering effect will be small;
If it exceeds % by weight, it is not preferable because it causes deterioration of properties at high temperatures, corrosion resistance, and spalling resistance.

The sintering aid is preferably added in the form of a fine powder of 74 μm or less, a slip, or a liquid. Furthermore, a zirconium salt such as zircosol or zirconyl hydroxide may be added as a sintering aid if necessary.

This invention combines the above-mentioned refractory raw materials and sintering aids,
After kneading, it is shaped and baked at 1600°C to 1900°C for 3 to 10 hours. If the firing temperature is below 1600°C, sufficient sintering cannot be achieved, and on the contrary, heating above 1900°C is economically disadvantageous.

〔Example〕

The above raw materials were blended in the proportions shown in Table 1, kneaded, formed into a dish shape, and fired at 1700° C. for 5 hours to obtain the zirconia refractory of the present invention.

On the other hand, the electric fused bathoderite talin force in Table 1 is C
A comparative product was produced by a conventional method by replacing the product with a partially stabilized zirconia clinker having a03molI2e% and firing at the same temperature and time as the product of the present invention.

Table 2 lists the results of measuring the porosity, bulk specific gravity, compressive strength, and amount of erosion in the corrosion resistance test for the products according to the present invention and the conventional method. The above corrosion resistance test was carried out using converter slag as the corrosive agent, and was carried out by the rotary erosion method.
After holding it at 0℃ for 3 hours, there was 1 melting loss!
t(am) was measured.

As is clear from Table 2, the product of the present invention is different from the conventional product.
Despite being comparable in porosity, bulk specific gravity, compressive strength, and cold and hot bending strength, it is significantly superior in corrosion resistance.

(Leaving space below) Table 1 Table 2 [Effects of the invention] As explained above, this invention has the advantage that the fused Baddeleyite talin force which does not cause tissue destruction at the crystal system transition temperature of 1200°C.
is used as the main component, it is possible to obtain a highly corrosion-resistant zirconia refractory that does not undergo the desulfurization electrification phenomenon and therefore does not suffer from a decrease in corrosion resistance.

Claims (1)

[Claims] 50% by weight or more of fused Baddeleyite clinker, 95
100 parts by weight of zirconia clinker having less than 1% by weight, and at least one of clay, alumina fine powder, and phosphoric acid.
After kneading 0.3 to 3 parts by weight of seeds and molding, 1600 to 1
A method for producing a zirconia refractory, characterized by firing at 900°C.