JPH0688828B2 - Refractory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The product of the present invention is a chromium-boron alloy with a refractory material containing graphite and / or a carbon material in a molar ratio of 1: 1 to 1: 2 (CrB to CrB ₂ ). TECHNICAL FIELD The present invention relates to graphite and carbonaceous refractory for iron making (for steel making) in which sintering ability is improved by mixing powder, and oxidation of graphite and carbon is reduced to prevent deterioration of quality.

(Prior art) The recent steel industry is developing new steelmaking methods, streamlining operations,
Due to the progress of efficiency and the rapid improvement of the quality of products, the refractory materials used here are under severer usage conditions. The operating conditions are high temperature, diversification of treatment, long time, etc., the operating temperature is high, and the reactivity between the melt and the refractory becomes large due to a sudden change, and it is retained for a long time. The usage conditions are becoming severe.

In order to cope with these severe operating conditions, heat resistant spalling resistance, structural spalling resistance due to the penetration of slag-based foreign matter, scientific erosion resistance, etc. are highly resistant to stable operation, and the service life is extended. Is strongly desired.

(Problems to be Solved by the Invention) At present, raw materials used to meet such requirements are moving toward high-purity, high-grade materials. And in order to fully utilize the characteristics of these selected materials and obtain a refractory material, adjust the particle size suitable for the material, perform kneading and high pressure molding to give a high packing density, and perform long-time firing at high temperature. Therefore, this alone is not sufficient, and graphite and / or carbon materials are further added, and the mixture is kneaded and molded with a suitable organic and / or inorganic binder, followed by low-temperature treatment to produce the product. However, when these graphite refractories are used, they are dried and preheated before they are actually used, but in the process up to the actual use, even during actual use, the surface layer oxidizes from the surface layer to become a porous structure and weakens. The excellent material properties of carbon and graphite cannot be fully utilized, and sufficient durability has not yet been achieved. For this reason, various anti-corrosion agents have been added, but they have not been sufficiently effective, and even their melt resistance is sometimes impaired.

(Means for Solving Problems) In view of the above situation, the present inventors have found that the carbon material added to improve the quality characteristics and the graphite material work effectively until the carbon material is added. The first condition is that it is not oxidized during use. Therefore, as a result of repeated research on various methods for preventing oxidation, it was found that chrome-boron alloy metal powder was used as a method for improving the overall quality characteristics (performance) of refractory materials.

The product of the present invention contains chromium (Cr) and boron (B) in a molar ratio of 1: 1 to
By adding chromium-boron alloy within the range of 1: 2 in the form of fine powder of 0.15 mm or less, the characteristics of carefully selected refractory materials, graphite and carbon materials can be fully utilized and 150
Boron acid (B ₂ O ₃ ), chromium oxide (Cr ₂ ) that takes advantage of the characteristics of the base material by low-temperature curing treatment at ~ 1000 ° C and also produces graphite and carbon by decomposition and oxidation at the surface layer of chromium boron-based material O ₃ ) improved the oxidation resistance, and it was possible to obtain a refractory having excellent heat resistance, corrosion resistance, and spalling resistance.

(Additional Effect of Graphite and / or Carbon Material) When graphite or carbon is contained in the refractory material, these materials will coexist in the joint portion due to the structure of the structure. The weakest point in the structure of the refractory is the joint part.Since this joint part is an aggregate part of fine particles, it has a much coarser texture state than coarse particles, and it easily allows foreign substances to enter, and thus a large alteration layer. It also has a high chemical reactivity. For this reason, the melting loss is large, and since an altered layer is generated due to the intrusion of foreign matter, this portion becomes heterogeneous during use, so that a crack is generated and eventually peels off, resulting in damage. It improves these phenomena. That is, by mixing graphite and carbon materials, which have very small wettability with the slag system, heat spalling resistance, the occurrence of cracks due to the penetration of slag and the occurrence of cracks, and eventually the phenomena such as flaking can be improved. At the same time, it has a great effect of increasing the chemical erosion resistance.

However, both graphite and carbon materials have a great drawback that they are oxidized.

◎ (Regarding the effect of addition of Taromuvolone alloy) In order to enhance the physical properties of refractory bricks, it is necessary to increase the interparticle bonding force of the materials used and form a dense structure.
Since highly purified materials, graphite and / or carbon materials are difficult to sinter, a sintering aid is added. The sintering aids used here are boric acid and its compounds, Na ₂ O, K
Materials containing ₂ O, CaO, MgO, LiO ₂ etc. are used. Among these, boric acid and its compounds are the sintering aids that have less adverse effect on the quality of refractory materials, but these are soluble in water. In addition, it has characteristics such that it moves to a high temperature portion under high temperature.

Therefore, when the molded body is dried, it is baked with the binder,
As it is heated, it moves to the surface layer. For this reason, a B ₂ O _{3 over-} multilayer is formed on the brick surface layer, heat resistance and erosion resistance are not greatly impaired, and the inner layer portion of the brick is insufficiently sintered (bonded), and a uniform brick with high sinterability is obtained. In many cases, other sintering aids are used because the properties of boric acid materials cannot be utilized and the quality is adversely affected. As a result of various studies, in order to improve such defects of the boric acid-based material and to make a more effective state, it can be improved by using a chromium-boron-based alloy fine powder. The chrome-boron alloy fine powder gradually separates into Cr and B from the operating surface during use of the refractory and is further oxidized to produce Cr ₂ O ₃ and B ₂ O.
Generates ₃ and.

Refractory Izure have high sintering effect between the Al ₂ O _3, MgO or the like is a representative component of the herein generated B ₂ O ₃ and Cr ₂ O ₃ works effectively each B ₂ O ₃ is refractory Form a dense layer on the working surface of an object. This dense layer forms a semi-molten layer with high viscosity at high temperature and has excellent physical properties, and at the same time, the outer surface layer forms a glass layer with a highly viscous anti-oxidation effect, thereby forming graphite or carbon. This will prevent the oxidation phenomenon. Also, Cr ₂ O ₃ improves the heat resistance of each of the components such as SiO ₂ , Al ₂ O ₃ , MgO, etc., and when used as a refractory material for ironmaking, a smaller amount than the operating layer When dissolution occurs, Cr ₂ O ₃ elutes in the slag. This eluted C
Since r ₂ O ₃ has the function of increasing the melting point of slag, the viscosity of slag can be increased by increasing the melting point, which significantly improves the chemical reaction capacity and improves corrosion resistance such as reducing melting loss of refractory materials. At the same time, by reducing the penetration of the slag into the refractory structure, the structural peeling due to the formation of the penetration layer (altered layer) is also improved. Due to the heat received during such use, a chromium-boron alloy acts to form a dense layer, and at the same time, it acts very effectively in preventing the oxidation of graphite and carbon. This material is produced by a hardening treatment at a low temperature, and thus the heat resistance spalling resistance against rapid heating and quenching can be improved.

As described above, this chrome-boron alloy decomposes and the oxidation reaction gradually progresses from the surface (operating surface), so that a refractory material having the characteristics of high melting point chrome boron is maintained and a sintered layer with a uniform operating surface is always formed. In addition, a highly viscous glass layer is formed on the outermost surface layer to protect graphite and carbon from oxidation and maintain stable quality. Therefore, even with a composite refractory made of graphite or carbon and a high-purity hardly-sinterable material, it is possible to manufacture a refractory in which the defects of the conventional similar materials are improved and the characteristics of the materials used are fully utilized.

[Reason for limitation] The reason why the chemical composition value of the chrome-boron alloy is 1: 1 to 1: 2 in the molar ratio of chromium to boron and Cr + B is 90% or more.

 When the content of B (boron) is 1: 1 or less in terms of molar ratio, the sintering effect is low and the improvement in physical quality is small.

When the content of B (boron) is 1: 2 or more in molar ratio When the content of boron is 1: 2 or more in molar ratio, the alloy composition is CrB.
_It becomes ₂ + B and contains free B (boron),
When added to the refractory material, free boron easily migrates in the structure and the target quality and stable and uniform quality cannot be maintained. In addition, the yield of materials decreases during alloy production, and the variations in composition also increase.

The reason why Cr + B is 90% or more The reason is that the addition amount is set to 0.5% to 10.0% and the increase in the amount of the impure component causes a defect that a low melt is formed in the base material.

 Reason for using powder of 0.15 mm or less The purpose of addition is to improve sinterability and corrosion resistance.

This addition is intended to improve corrosion resistance and slag penetration resistance, thereby enhancing melting loss and thermal and structural spalling properties. For this purpose, the alloy decomposes and oxidizes to act respectively, and it is more effective to have a grain size of 0.15 mm or less, and if it is coarse, its effect becomes small.

Reasons for setting graphite and / or carbon material to 5% to 30% Graphite and carbon are important materials for modifying the bonding portion. The effect of addition, including usage conditions, needs to be 5% or more. Again 30
The reason why the content is up to 30% is that when the content exceeds 30%, the strength of the refractory material itself is deteriorated and problems of oxidation occur.

Examples Next, the examples of the present invention will be described in detail. Table 1 shows the chemical component values of the raw materials used in the examples.

Using the above raw materials Example (1) Addition amount of chromium and boron alloy Example (2) Particle size of chromium and boron alloy Example (3) Blending amount of graphite and carbon material Example (4) Chromium and boron Examples of differences in the chemical composition values of alloys are shown below. After kneading and molding the compounds shown in Table 1 at a pressure of 1000 kg / cm ² , 350 ° C.
Curing treatment is performed to produce a test piece.

(Effects of the Invention) The added amount of the chromium-boron alloy of the embodiment increases as the added amount of the oxidation resistance of graphite carbon increases. The amount of oxidation is 35% at 3% and 13.2% at 12% compared to the non-added product, which is very small, and is sufficiently effective for oxidation protection under general use conditions. In addition, the quality characteristics of refractories have little change at low and medium temperatures, and can maintain compactness, which results in 49% to 31% and 78% in erosion resistance and slag permeability, respectively.
Stay at ~ 33%. However, if the amount of addition is 12%, there is a drawback that the corrosion resistance becomes low. Regarding the grain size of the chromium-boron alloys of Examples, the effect is small when the grain size becomes 0.5 mm or less and 0.3 mm or less, and the effect is recognized when it is 0.15 mm or less.

When the blending amount of the graphite carbon material in the example is 3%, the corrosion resistance and the slag permeability cannot be sufficiently improved.
At 33%, the quality of the structure deteriorates at high temperatures during use, and the permeability of the slag and the amount of erosion are greatly reduced.

From the chemical composition values of the chromium boron alloy in Example (4),
When Cr is higher than 1: 1 and Cr is higher than 1: 1, sinterability and oxidation resistance are not improved, and when B is higher than 1: 2, the structure becomes brittle at high temperatures, resulting in corrosion resistance and heat resistance. You will lose your sexuality. As shown in the results such as the above, in the product of the present invention, the generation of the deteriorated layer due to the penetration of the slag into the structure is extremely reduced and the chemical erosion resistance can be greatly improved and the structure can be improved. The strength in the temperature range was stable, surface peeling, cracking, etc. could be improved, and structural defects were also improved.

Claims (1)

[Claims] 1. A refractory material consisting of one or two or more graphite and / or carbon materials in an amount of 5% to 30%, and chromium and boron in a molar ratio of 1: 1 to 1: 2 and an impure component within 10%. Characterized by adding 0.5% to 10% by weight of powder of a chromium boride alloy having a particle size of 150 μm or less, kneading and molding using an appropriate organic and / or inorganic binder, and curing at 150 ° C. to 1000 ° C. Graphite refractories for steelmaking.