JPH0782005A - Low-carbon magnesia-carbon-based refractory - Google Patents

Abstract

PURPOSE:To prevent occurrence of structural spalling caused by slag permeation in combination with suppression of thermal spalling of low-carbon magnesia.carbon-based refractory and to check damage such as cracking of refractory resulting from the occurrence. CONSTITUTION:This low-carbon magnesia.carbon-based refractory comprises 1-10wt.% of a carbonaceous material, 0.1-3wt.% of titanium nitride and/or titanium oxide, optionally <=3wt.% 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-carbon 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. Further, magnesia carbon brick has also been widely used as a refractory material for lining molten metal containers such as converters and ladles. However, in recent melting of ultra-low carbon steel, there is a demand for refractory materials containing no carbon, or even containing carbon as low as possible.

[0003]

As described above, when a basic refractory mainly containing a magnesia material containing no carbon is used in the molten metal container, the basic refractory has excellent slag corrosion resistance. When the low-viscosity slag that has penetrated into the refractory penetrates deep into the refractory and solidifies, structural spalling occurs due to the difference in the coefficient of thermal expansion between the magnesia part and the slag part, causing the refractory to peel off. It happens. The penetration of slag into this basic refractory is remarkable in unfired bricks and amorphous refractories having a higher porosity than in fired bricks.

In addition, carbonaceous materials such as graphite are added to ordinary magnesia carbon bricks in an amount of 12 to 25% by weight.
A content of less than or equal to wt% is desirable. However, if the carbonaceous material is less than 10% by weight, the same heat sprinkling and structural spouring as magnesia bricks are generated, and sufficient durability cannot be obtained.

It is known that a method of adding chromium oxide and use of magro bricks are used to reduce the sparking caused by the penetration of slag. However, the chromium oxide component is a material that we do not want to use in terms of environmental protection.

[0006]

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 low carbon magnesia carbon containing 1 to 10% by weight of a carbonaceous material, 0.1 to 3% by weight of titanium nitride or / and titanium carbide, and the remainder being a refractory material mainly containing magnesia. Bon-based refractory. Furthermore, 3% by weight of boric acid and phosphoric acid glass
It contains the following: 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 a synthetic material 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.

As the carbonaceous material, natural graphite, artificial graphite,
Petroleum coke, carbon black, etc. can be used,
From the viewpoint of corrosion resistance at high temperatures, graphite, which is also highly pure, is suitable. The amount of the carbonaceous material used is 1 to 10% by weight. If the carbonaceous material exceeds 10% by weight, the problem of carbon pickup will occur, and conversely 1% by weight of the carbonaceous material will occur.
If it is less than, there is no slag penetration preventing effect of the carbonaceous material,
The anti-spooling property becomes remarkably inferior, which is not preferable.

Titanium nitride and titanium carbide, which are the features of the present invention, are used alone or in combination. The amount is 0.1 to 3% by weight in the refractory. If the amount of titanium nitride or titanium carbide is less than 0.1% by weight, a sufficient slag permeation suppression effect will not be exhibited, and since it is used in combination with a carbonaceous material, if it exceeds 3% by weight, corrosion resistance will only decrease. Yes, 3% by weight or less is sufficient.

Further, when the low carbon magnesia / carbon type refractory material of the present invention is used in a violently oxidizing atmosphere, if a glassy material is added as an antioxidant for titanium nitride or titanium carbide, Good. Boric acid-based, phosphoric acid-based, or boric acid-phosphoric acid-based glass is suitable as the glassy material, and silicate-based glass reacts with slag and magnesia to form a component with a low melting point, so it is preferable to avoid it. In particular, P ₂ O ₅
40-55 mol%, M ₂ O (M represents an alkali metal) 30 to 60 mol%, glassy or consisting of B ₂ O ₃ 10 mol% or less, the M ₂
O for other alkaline earth oxides, Al ₂ O ₃ , SnO, Zn
Glassy materials substituted with O, PbO, etc. are preferable. The glassy material may be water-soluble or water-insoluble. If glassy material is added, the amount is 3% by weight in the refractory.
Below. If the amount exceeds 3% by weight, the corrosion resistance decreases, which is not preferable. In the present invention, titanium carbide is superior in oxidation resistance to titanium nitride.

Since the refractory material of the present invention contains a small amount of carbonaceous material, it has a problem of oxidation. Oxidation of carbonaceous materials is considerably suppressed by the addition of titanium carbides or nitrides or vitreous substances, but in order to impart further oxidation resistance, metal powders such as aluminum, silicon, magnesium, calcium and their It is also possible to add one or more alloys.

In the method for producing a low carbon magnesia-carbon refractory of the present invention, when used as a regular refractory, the raw materials are weighed in accordance with a conventional method, a binder is added, and the mixture is kneaded and then pressed. Mold. This is used as it is or as a non-fired brick by heat treatment at a temperature of 600 ° C or less. As the binder, organic binders such as phosphate, silicate, and phenol resins 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. It is also possible to use it in a non-aqueous system using an organic binder such as a phenol resin.

[0014]

[Function] Refractory materials mainly composed of magnesia and 10
If the carbonaceous material is contained only by weight% or less, the penetration of slag cannot be sufficiently suppressed and structural spooling is likely to occur.Therefore, graphite with a particle size of about 100 to 1000 μm is usually used. By setting the particle size to a few tens of μm or a few μm or less, the small addition amount can be covered by increasing the specific surface area.
Even if you try to do so, this time the loss due to oxidation becomes severe, which is counterproductive. However, in the case of ordinary graphite having a particle size of about 100 to 1000 μm, the addition of 10% by weight or less cannot sufficiently suppress the penetration of slag from between magnesia fine particles.

The titanium nitride or carbide of titanium used in the present invention has a remarkably low wettability with respect to slag. Therefore, like graphite, the slag is prevented from penetrating deep into the interior, and the structure sponge associated with the penetration of slag is suppressed. Prevent the ring. Also, in the case of titanium carbide or titanium nitride, there is no concern about carbon pickup to the steel, and even if it is used with a particle size of several tens of μm or several μm or less, it is highly resistant to oxidation and may be lost by oxidation. Also few. Therefore, by adding a small amount of titanium carbide or titanium nitride to a material composed of a refractory material mainly containing magnesia and a carbonaceous material of 10% by weight or less, the penetration of slag can be suppressed very well.

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

During the use of the refractory material of the present invention, titanium nitride and carbide prevent penetration of slag due to its low wettability to the slag, but when these are oxidized, the slag forms a magnesia material. 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.

[0018]

[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 heat treatment method column of Tables 1 and 2 is that dried at 150 ° C for 24 hours, "heat" is heat treated at 300 ° C for 10 hours, and "baked" is 1700 ° C for 20 hours. It was baked. The physical properties of the sample thus manufactured are also shown in Tables 1 and 2.

For the slag test, a rotary slag test furnace and a propane-oxygen burner were used and the temperature was maintained at 1650 to 1700 ° C. for 3 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%, CaO 33
%, MgO 5%, C / S = 1, and a new one was replaced every hour. In the results of Tables 1 and 2,
"None" indicates that almost no cracks were found on the cut surface of the sample after the test, "Large" indicates that large cracks were found, "Medium" indicates that moderate cracks were found, "small"
Is a small crack. The thickness of the permeation layer is indicated by the thickness of the densified portion from the back of the working surface to the inside of the brick.

Spooling resistance test was melted in 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. For those with no cracks, the second and subsequent immersions were performed, and the state of cracks at the time of cracking was observed. The crack size is expressed in the same way as in the slag test.

[0021]

[Table 1]

[0022]

[Table 2]

The slag test of Tables 1 and 2 also shows that the samples containing titanium nitride and carbide of the present invention (Examples 1 to 8) all have low carbon quality magnesia carbon brick ( Compared to Comparative Example 1) and Maguro brick (Comparative Example 7), the permeation thickness of the slag is very small, and the structure support
Almost no cracks were observed due to the ring, and there was little melting loss. Further, when glassy material is added together with the titanium compound, although not clearly shown in the table, the result that the oxidation of the titanium compound is suppressed is obtained. However, it can be seen that if the amount of the titanium compound or the glassy substance is too large (Comparative Examples 2, 3, 5), the amount of erosion increases even if the penetration of slag can be prevented to some extent.

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 small cracks were observed in the second and subsequent tests. On the other hand, in those containing no titanium compound (Comparative Examples 1, 4, 6, and 7), considerable cracks were generated in the first or second test, which caused a large difference from the refractory of the present invention, and the fire resistance of the present invention. It can be seen that the product has excellent heat-resistant spooling property.

[0025]

According to the present invention, low carbon magnesia
By adding titanium nitride or carbide to the carbon-based refractory, it is clear from the results of the examples that the penetration of slag into the refractory is prevented and the refractory by the structural spooling is applied. It is possible to minimize the damage of the. Also, it has excellent heat-resistant spooling and slag corrosion resistance. Further, by adding 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. A low carbon material containing 1 to 10% by weight of a carbonaceous material, 0.1 to 3% by weight of titanium nitride or / and titanium carbide, and the balance being a refractory material mainly containing magnesia. Quality magnesia carbon refractory. 2. Containing 1 to 10% by weight of carbonaceous material, 0.1 to 3% by weight of titanium nitride or / and titanium carbide, boric acid, phosphoric acid type glassy material of 3% by weight or less, and the balance mainly composed of magnesia. Low-curve characterized by being made of refractory material
Bon-based magnesia-carbon refractory.