JPH0782001A - Magnesia refractory composition - Google Patents

Abstract

PURPOSE:To prevent occurrence of structural spalling caused by slag permeation in combination with suppression of thermal spalling of refractory consisting essentially of a magnesia material and to check damage such as cracking of refractory resulting from the occurrence. CONSTITUTION:This magnesia refractory composition comprises 0.1-5wt.% of titanium nitride and/or titanium oxide, optionally <=5wt.% of a borate or phosphate-based glass and the rest of a refractory material consisting essentially of magnesia.

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, even in the recent melting of ultra-low carbon steel, there is a risk of carbon pickup even with a low carbon content magnesia carbon brick, and magnesia brick is also used.

[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]

The present inventors have reached the present invention by paying attention to titanium nitrides and carbides as a result of investigating the penetration of slag and also considering the corrosion resistance of refractory materials. That is, the present invention is a magnesia refractory composition comprising a refractory material containing titanium nitride or / and titanium carbide in an amount of 0.1 to 5% by weight, and the balance being mainly magnesia. Furthermore, it is a magnesia refractory composition containing 5% by weight or less of boric acid and phosphoric acid glass. Further, the refractory material of the present invention is characterized in that it can be used not only in the non-fired standard refractory material but also in the form of the non-standard 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.

Titanium nitride and titanium carbide, which are features of the present invention, are used alone or in combination. The amount is 0.1 to 5% by weight in the refractory. When the amount of titanium nitride or titanium carbide is less than 0.1% by weight, a sufficient slag permeation suppression effect is not exhibited, and when it exceeds 5% by weight, corrosion resistance is deteriorated, which is not preferable.

Further, when the magnesia refractory composition of the present invention is used in an oxidizing atmosphere, a vitreous material may be added as an antioxidant for titanium nitride and titanium carbide. The glassy material is preferably boric acid-based, phosphoric acid-based, or boric acid-phosphoric acid-based glass, and silicic acid-based glass is slag,
It should be avoided as it reacts with magnesia to form low melting point components. In particular, a glassy substance composed of 40 to 55 mol% of P ₂ O _5, 30 to 60 mol% of M ₂ O (M is an alkali metal), and 10 mol% or less of B ₂ O ₃ and M ₂ O of this kind to other alkaline earths. Glass materials substituted with oxides such as Al ₂ O ₃ , SnO, ZnO and PbO are preferable. The glassy material may be water-soluble or water-insoluble. When the glassy material is added, its amount is 5% by weight or less in the refractory material. If the amount exceeds 5% by weight, the corrosion resistance decreases, which is not preferable. In the present invention, titanium carbide is superior in oxidation resistance to titanium nitride.

In the method for producing a magnesia refractory composition of the present invention, when it is used as a regular refractory material, the raw materials are weighed according to a conventional method, a binder is added, and the mixture is kneaded and then press-molded. This is used as it is or as a non-fired brick by heat treatment at a temperature of 600 ° C or less. As a binder, phenol
Any of organic binders such as resin and inorganic binders such as sodium silicate, phosphate and bitter juice can be used. It is desirable that the phenol resin has a low non-volatile content and is easily volatilized or decomposed and lost during the temperature rising process.

The amorphous refractory is mainly used as a cast material, but other forms are also usable. Also in this case, a raw material, a binder, a dispersant, a plasticizer, a curing modifier and the like are appropriately selected and mixed with water and other solvents in a conventional manner. Alumina cement as a binder,
Sodium silicate, phosphate, etc. can be used.

[0010]

The titanium nitride or carbide of the present invention has a low wettability with respect to slag and therefore suppresses deep penetration of slag into the interior of the brick, and prevents structural spooling accompanying penetration of slag. Also, even if titanium carbide is used,
No worries about Bon pickup.

Further, titanium nitride or carbide has a thermal conductivity of 10 kcal / m · hr · ° C or more, and that of magnesia is about 4 kcal / m · h.
Higher than r ・ ° C and highly effective for heat sparring.

During use of the refractory material of the present invention, titanium nitride and carbide have low wettability with respect to the slag and prevent penetration of the slag. Since the reaction is small, it penetrates into the refractory, but the oxidized titanium oxide melts into the slag at this time, increasing the viscosity and preventing the penetration of the slag into the refractory. In addition, slag component CaO,
Ca reacts with SiO ₂ , Al ₂ O ₃ and Fe oxides
TiO ₃ , MgTiO ₃ , (Mg, Fe) ₂ SiO ₄ , Mg
It precipitates as Ti ₂ O ₄ , etc., takes in the slag component and at the same time closes the pores, densifies the refractory, helps prevent the penetration of slag, and contributes to improving the sponging resistance of the refractory. In addition, these compounds also have the effect of coating the surface of the remaining titanium nitride or carbide, and exhibit the effect of suppressing the progress of oxidation.

[0013]

[Examples] Trials were made using materials and binders having the compositions shown in Table 1. Similarly, as a comparative example, a sample having the composition shown in Table 2 was prepared. The formulations in Tables 1 and 2 are all expressed in parts by weight. The molding methods "P" in Tables 1 and 2 are kneaded and press-molded according to a conventional method, and "V" is vibration-cast using a rod-shaped vibrator after adding water to the material. Is. Similarly, “dry” shown in the firing column of Tables 1 and 2 is that dried at 150 ° C. for 24 hours, and “heat” is heat treated at 300 ° C. for 10 hours.
Is baked at 1700 ° C. for 20 hours. The physical properties of the sample thus manufactured are also shown in Tables 1 and 2.

The slag test uses an induction furnace at 4 at 1650 ° C.
Held for hours. The results are shown in Tables 1 and 2. The slag composition is Al ₂ O ₃ 15%, SiO ₂ 33%, Fe ₂ O ₃ 14%, C
33% aO, 5% MgO and C / S = 1 were used. In the results of Tables 1 and 2, “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 “middle” indicates Medium cracks were seen. In the case of titanium nitride or carbide, the slag penetrates only into the oxidized layer, and the penetration depth of the penetration slag, that is, the thickness of the oxide layer.

Spooling resistance test was melted in an induction furnace
A sample of 40x40x114 mm was immersed in hot metal at 1400 ° C, taken out after 3 minutes, and naturally cooled, and the state of cracks was observed. Those with no cracks were further immersed for the second time, and the state of cracks at the time of cracking was observed.

[0016]

[Table 1]

[0017]

[Table 2]

The slag tests of Tables 1 and 2 also show that the samples containing titanium nitride and carbide of the present invention (Examples 1 to 7) were all magnesia bricks (Comparative Example 1),
Compared to Magkuro brick (Comparative example 4) or Magnesia spinel brick (Comparative example 5), the penetration depth of slag is very shallow, there are almost no cracks that are likely to be caused by structural spooling, and there is also no melt damage. Fewer results were obtained. In particular, the vitreous substance is added together with the titanium compound (Example 4).
~ 7), further favorable results are obtained because the oxidation of the titanium compound is suppressed. However, if the amount of the titanium compound or the vitreous substance is too large (Comparative Examples 2 and 3), the erosion of the slag can be prevented to some extent, but the amount of melting loss increases.

Further, as can be seen from the results of the heat spooling test, in the sample of the present invention, no cracks were generated in the first test, and only a small crack was observed in the second test. On the other hand, in the case of containing no titanium compound (Comparative Examples 1, 4, and 5), cracks were generated in the first test, and it can be seen that the refractory material of the present invention is excellent in heat-resistant spooling property.

[0020]

According to the present invention, by adding a titanium nitride or a carbide to a basic refractory composed mainly of a magnesia material, as is clear from the results of the examples, the slag in the refractory is clarified. It is possible to prevent the permeation of the refractory and minimize the damage to the refractory due to the structure spooling.
Also, it has excellent heat-resistant spooling and slag corrosion resistance. Furthermore, by adding a phosphoric acid-based or boric acid-based glassy material, the oxidation of the added titanium compound is suppressed, and the effect of the titanium compound is further exerted.

Claims (2)

[Claims] 1. Titanium nitride and / or titanium carbide
A magnesia refractory composition containing 0.1 to 5% by weight, and the balance being a refractory material mainly containing magnesia. 2. Titanium nitride or / and titanium carbide
A magnesia refractory composition containing 0.1 to 5% by weight, boric acid and phosphoric acid type glassy material 5% by weight or less, and the balance being a refractory material mainly containing magnesia.