JPH06227857A - Magnesia refractory - Google Patents

Abstract

PURPOSE:To obtain a magnesia refractory effective for preventing the infiltration of slag into the refractory and suppressing the structural spalling damage to the refractory by compounding a specific amount of zinc oxide to a refractory material composed mainly of magnesia. CONSTITUTION:The magnesia refractory consists of a refractory material containing 0.1-20wt.% of zinc oxide (in terms of ZnO) and the remaining part composed mainly of magnesia. The refractory material composed mainly of magnesia is e.g. known magnesia refractory such as electromelted magnesia clinker, sintered magnesia clinker and natural magnesia clinker or a mixture of the above compositions with synthetic or natural dolomite or magnesia- alumina spinel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory material mainly composed of magnesia material used for various molten metal containers such as a converter and a ladle.

[0002]

2. Description of the Related Art In recent years, refractory linings of molten metal containers such as ladles are mainly refractory mainly composed of rock from alumina mainly refractory from the viewpoint of slag corrosion resistance as operating temperature rises. The material is changing. Furthermore, magnesia carbon bricks are also widely used as refractories for lining molten metal containers such as converters and ladles. However, in recent years, low-carbon magnesia carbon bricks and magnesia bricks have been used for the melting of ultra-low carbon steel.

[0003]

As described above, when a basic refractory material mainly containing a magnesia material not containing carbon is used in a molten metal container, another obstacle has occurred. . That is, since this basic refractory has excellent slag corrosion resistance, if the low-viscosity slag that has penetrated into the refractory penetrates deep into the refractory as it is and solidifies, the difference in the coefficient of thermal expansion between the magnesia part and the slag part As a result, structural sparking occurs, and a phenomenon occurs in which the refractory material peels off. The penetration of slag into this basic refractory is remarkable in unfired bricks and amorphous refractories having a higher porosity than in fired bricks. A method of adding chromium oxide to reduce the penetration of slag is known. However, chromium oxide is a material that we do not want to use as an environmental measure.

[0004]

Means for Solving the Problems As a result of studying the penetration of slag and taking into consideration the corrosion resistance of refractory materials, the present inventors have found that zinc oxide forms a solid solution with magnesia and has a particularly low melting point. The inventors arrived at the present invention by paying attention to the fact that such compounds are not produced. That is, the present invention is a magnesia refractory material which is made of a refractory material containing zinc oxide in an amount of 0.1 to 20% by weight as ZnO and the balance being mainly magnesia. Further, the refractory material of the present invention has a feature that it can be used in any form such as a fired or non-fired fixed shape refractory material or an amorphous refractory material.

The magnesia-based refractory material used in the present invention may be a known magnesia refractory material such as an electrofused magnesia clinker, a sintered magnesia clinker or a natural magnesia clinker, or may be synthesized with these materials. Alternatively, it can be used as a mixture with a natural dolomite clinker or magnesia-alumina spinel. From the viewpoint of slag corrosion resistance, it is preferable that MgO content of these refractory materials is 50 wt% or more.

The zinc oxide which is a feature of the present invention is
ZnO, Zn ₂ O, ZnO _{2 and the} like are known, and any form of zinc oxide can be used in the present invention.
Zinc oxide containing nO as a main component is generally used. The amount of ZnO is 0.1 to 20% by weight in the refractory, preferably 1
~ 10% by weight. If the amount of zinc oxide is less than 0.1% by weight, a sufficient slag permeation suppression effect will not be exerted, and if it exceeds 20% by weight, the refractory will oversinter during use and cause spooling and corrosion resistance. Also decreases, which is not preferable. In the present invention, as the zinc oxide, zinc hydroxide, zinc carbonate, zinc nitrate, zinc sulfate, zinc chloride, zinc acetate, zinc oxalate, or the like, which changes into zinc oxide during firing or use, can also be used.

The method for producing a magnesia refractory material according to the present invention, when used as a standard refractory material, follows a conventional method,
A refractory material mainly containing magnesia, zinc oxide, and other raw materials are weighed, a binder is added, and the mixture is kneaded and press-molded. It can be used as it is or as a non-fired brick by heat treatment at a temperature of 1000 ℃ or less.
It can also be used as a fired brick fired at a temperature higher than ° C. As the binder, any of organic binders such as phenol resin and inorganic binders such as soda silicate, phosphate and bittern can be used.

The amorphous refractory material is mainly used as a casting material, but in the usual manner, a refractory material, a zinc oxide, a binder, a dispersant, a plasticizer, a curing modifier, etc. are appropriately selected. , Mixed with water and other solvents. As the binder, alumina cement, sodium silicate, phosphate or the like can be used.

[0009]

[Function] The zinc oxide of the present invention has a coefficient of thermal expansion of 7x10.
^-6 / ℃, which is much smaller than 14x10 ^-6 / ℃ of magnesia, has the effect of relaxing the thermal expansion of magnesia, and is effective in improving the heat-resistant spooling of refractory materials. This effect is due to alumina and chromia (both have a thermal expansion coefficient of about 8
x10 ^-6 / ℃) is more remarkable.

Further, the added zinc oxide is almost exclusively Mg _{x in} magnesia during use or during firing during production.
It forms a solid solution as Zn _1-x O and contributes to the sintering of the refractory material. Since zinc oxide does not form a compound with a specific low melting point together with magnesia, it does not significantly reduce the fire resistance of refractory materials.

During the use of the refractory material of the present invention, the slag has a small reaction with the magnesia material, so that it penetrates deeply into the refractory material. At that time, the zinc oxide solid-dissolved with magnesia melts into the slag material. It increases the viscosity and prevents the slag from penetrating into the refractory. Further, CaO slag components, SiO _2, Al ₂ O ₃ and CaZnSi reacts with such as Fe oxide _{2 O 7, Zn 2 SiO 4} , ZnAl 22 O 37,
Precipitates as Mg ₂ SiO ₄ , (Mg, Fe) ₂ SiO _4, etc., takes in the slag component and at the same time closes the pores, densifies the refractory, helps prevent slag penetration, and sponging resistant refractory Contributes to the improvement of sex.

[0012]

[Examples] Trials were made using materials and binders having the compositions shown in Table 1. The formulations in Table 1 are all expressed in parts by weight. The molding method "P" in Table 1 is kneading and press molding according to a conventional method, and "V" is vibration casting using a rod-shaped vibrator after adding water to the material. . Similarly, "dry" in the firing column of Table 1 is 15
It was dried at 0 ℃ for 24 hours.
The one baked for 0 hours and the "baked 2" are those baked at 1700 ° C. for 20 hours. The physical properties of the sample thus manufactured are also shown in Table 1.

The slag test also serves as a structural spooling test. A rotary slag test furnace is used to perform a total of 3.5 hours at 1600 to 1650 ° C. with an oxygen-propane burner, and one hour after the set temperature is reached. The operation of turning off the burner and performing forced air cooling with a fan for 30 minutes was performed three times. The results are shown in Table 1. The slag composition was Al ₂ O ₃ 13.9%, SiO ₂ 1
6.0%, Fe ₂ O ₃ 20.3%, CaO 40.1%, ZnO ₂ 4.5
%, MgO 5.2%, and C / S 2.5. In the results of Table 1, "none" indicates that almost no cracks were observed on the cut surface of the sample after the test, "large" indicates that the sample was separated by a large crack, and "medium" indicates medium. It is the crack of.

In addition, the thermal spooling test was performed in air at 10
After heating the sample to each temperature of 100 ℃ increments between 00 and 1500 ℃,
This is the temperature at which cracking occurred after forced air cooling.

[0015]

[Table 1]

As can be seen from the results of the slag test in Table 1, samples containing the zinc oxide of the present invention (Examples 1 to 1)
Compared to those containing no zinc oxide (Comparative Examples 1, 3 to 5), 6) had a very shallow penetration depth of slag, and almost no cracks were observed due to structural spooling. The result was that there was little melting loss. However, if the amount of zinc oxide is too large (Comparative Example 2), penetration of slag can be prevented to some extent, but the amount of erosion is increased.

Further, the temperature at which cracks occur in the sample of the present invention is also magnesia brick (comparative example 1), magcro brick (comparative example 3), or magnesia spinel brick (comparative example 5), even when the heat sporing test is performed. ) Compared to
It can be seen that the refractory material of the present invention is excellent in heat-resistant spooling because it is higher by 200 to 300 ° C.

[0018]

INDUSTRIAL APPLICABILITY In the present invention, by adding zinc oxide to a basic refractory material mainly composed of magnesia material, the penetration of slag into the refractory material can be prevented, as is clear from the results of the examples. By doing so, it is possible to minimize damage to the refractory due to the structural spooling. Also, it has excellent heat-resistant spooling and slag corrosion resistance.

Claims (1)

[Claims] 1. A magnesia refractory material containing zinc oxide as ZnO in an amount of 0.1 to 20% by weight, and the balance being a refractory material mainly containing magnesia.