JPH0688830B2 - Refractory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applied to ironmaking which is rich in sinterability and reduces the fire resistance of graphite and carbon materials to prevent deterioration of quality due to oxidation and enhances residual expansion. The present invention relates to a refractory material containing graphite or a carbon material.

(Prior art) In the recent steel industry, since the development of new steelmaking methods, the rationalization of operations, and the improvement of efficiency have been promoted to improve the quality and the productivity rapidly, the refractory used here is also used. Usage conditions are becoming more and more severe. Regarding the usage conditions, the temperature rises and the temperature changes greatly due to the diversification of treatment. The usage conditions for refractory materials are becoming severe due to various factors such as the composition change range of slag for a long time becoming large.

The characteristics that the refractory must have in order to correspond to these various usage conditions are that it has high heat-resistant spalling property, that structural peeling due to the penetration of foreign matter such as slag into the tissue, and the occurrence of cracks are small, It is necessary to satisfy the properties such as high chemical erosion performance. With these characteristics, highly stable operation is possible, and the extension of life is strongly desired.

(Problems to be Solved by the Invention) At present, in response to such demands, raw materials have been moving toward higher purification and higher grades. In order to obtain refractory bricks that make the best use of the characteristics of these selected materials, the particle size is adjusted according to the material, high-pressure molding is performed through kneading, and high density is attempted. It is manufactured by adding materials.

Although improved by the addition of graphite and / or carbon material, the graphite and carbon materials added during this process of actual use, in which drying and preheating after construction are repeated before use and repeated use during use, from the surface layer As the oxidation progresses and the structure becomes brittle, the characteristics of the refractory used cannot be fully utilized.It has been proposed recently to add fine powder of chromium-boron alloy as a countermeasure against this oxidation. While the refractory itself receives heat during use, it shrinks. Since it is a so-called residual shrinkable material, it is the present situation that the joint properties of the brick joints cause openings and the material has a semi-cylindrical shape and the material characteristics cannot be sufficiently obtained.

(Means for Solving Problems) In view of such a situation, the present inventors have found that the graphite or carbon material added to improve the quality characteristics works effectively and has a residual shrinkage even when receiving heat during use. As a result of various studies for obtaining a smooth monolithic working surface without causing the above, it was found by adding fine powder of aluminum and / or aluminum alloy together with addition of chromium-boron alloy.

The product of the present invention contains chromium (Cr) and boron (B) in a molar ratio of 1: 1 to
Chrome boron alloy in the range of 1: 2 and Al and / or A
A product that can be produced by fully utilizing the characteristics of refractory materials and materials such as graphite carbon that have been carefully selected by adding alloys in the form of fine particles of 0.15 mm or less, and by hardening at a low temperature range of 150 ° C to 1000 ° C. Is.

That is, the chromium-boron alloy material prevents the oxidation phenomenon of graphite and carbonaceous material and prevents the heat resistance due to the action of boric acid (B ₂ O ₃ ) and chromium oxide (Cr ₂ O ₃ ) generated by decomposition and oxidation on the surface layer of the refractory. To improve the properties of Al and / or Al alloys, the spinel (MgO, Al ₂ O ₃ ) and mullite (3Al ₂ O
_3, 2SiO ₂₎ oxidation resistance by to forming a heat resistance may characteristics greatly improved corrosion resistance is equal to heat spalling resistance structural scan conventional refractories such as also enhancing the polling of the enhanced That is what I found.

(Additional Effect of Graphite and / or Carbon Material) When graphite or carbon is contained in the refractory material, these materials will coexist in the tissue-structured joint portion. The weakest part of the refractory structure is the coarsest part of the joint, which is a collection part of the fine particles of the material, and it easily reacts with foreign substances and allows the invasion into this structure. Therefore, the chemical erosion is large and an altered layer is formed to form a heterogeneous structure in the working layer. Due to this, cracking progresses to peeling and abnormal damage is caused. However, by adding graphite or a carbon material to this portion, the above-mentioned drawbacks can be improved. However, both the graphite and the carbon material have a great drawback that they are easily oxidized, such as being extinguished by oxidation to weaken the structure and make them porous.

(Regarding the effect of addition of chrome boron alloy) By mixing chrome boron alloy powder, it gradually decomposes from the operating surface during use and further oxidizes to Cr and B, respectively, so that Cr ₂ O ₃ and B ₂ O ₃ are generated. To generate.

CrB➝Cr + B➝Cr ₂ O ₃ + B ₂ O ₃ CrB ₂ B ₂ O ₃ and Cr ₂ O ₃ generated here work effectively respectively as described later.

B ₂ O ₃ is harming the material properties since Izure be sintered effective and less influence on the properties between the MgO and Al ₂ O _3, or the like which is a typical component and is moreover difficult to sinter the refractory Without forming a dense layer in the working layer of the refractory, this dense layer has high viscosity at high temperature and retains excellent physical properties, and at the same time has a highly viscous and highly antioxidant glass layer on the outermost layer. This results in the effect of preventing the oxidation phenomenon of graphite and carbon.

Cr ₂ O ₃ has the effect of forming spinel (picromchromite MgO, Cr ₂ O ₃ ) between each component of MgO, Al ₂ O ₃ and SiO ₂ and also greatly improving heat resistance and It elutes in the slag, and the melting point is raised to improve the heat resistance of the slag, and the viscosity of the slag is increased and the chemical reactivity is significantly reduced. Structural spalling is also improved because the permeation into the brick structure is suppressed and the generation of an altered layer due to permeation is reduced.

Since this boron alloy gradually decomposes and oxidizes from the surface layer, it can maintain a stable state in which a uniform sintered layer can be always maintained.

(Effect of use of Al or Al alloy) Al or Al alloy oxidizes during use to become highly active oxide and reacts with MgO in the refractory or SiO ₂ to form spinel or mullite _{Al → Al 2 O 3 + SiO} 2 → 3Al 2 O 3, 2SiO 2 - improving耐異product permeability and heat resistance spalling properties by forming a spinel or mullite with a result Izure also volume expansion and generation of mullite . It is possible to obtain a refractory that contains graphite and carbon and that has the advantage of using the characteristics of the material used by improving the drawbacks of conventional allotrope materials even with composite refractories of refractory sinter-resistant materials. It is a thing.

Reasons for limitation The reason why the chemical composition of the boron-chromium alloy is a molar ratio of metallic chromium and boron of 1: 1 to 1: 2 and Cr + B is 90% or more, and the content of B (boron) is 1: When it is 1 or less, 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), and when added to the refractory material, free boron easily migrates in the structure and the target quality and stable 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 90% or more of Cr + B is added. The added amount is 0.5% to 10.0%, and when the impurity content increases, there is a drawback that a low melt is formed in the base material. The reason why the powder is less than 0.15 mm Addition of chrome boron alloy The purpose is to improve sinterability and fire resistance.

This effect is to improve the corrosion resistance and the slag permeation property, thereby improving the melt damage resistance and the heat resistant structural spalling property. For this purpose, the decomposition and the oxidation of the alloy play their respective roles. Al or Al alloy oxidizes to form highly active refractory. This is spinel (MgO-Al ₂
O _3), mullite _{(3Al 2 O 3, 2SiO 2} ) and the like larger particle size for forming to is to reduce the residual expansion of the slag penetration resistance reactivity becomes poor efficiency is reduced. Therefore, it is effective to set the particle size to 0.15 mm or less.

Reasons for setting graphite and / or carbon material to 5% to 30% Graphite and carbon are important materials for modifying the bonding portion, and the addition amount is required to be 5% or more depending on the usage conditions. The reason why the content is up to 30% is that if the content exceeds 30%, the strength of the refractory itself and the problem of oxidation occur.

Example Next, an example of the present invention will be described in detail.

1. The chemical component values of the raw materials used in the examples are shown in Table-1.

Using the above raw materials Table-2 Addition amount of metal powder (Cr-B alloy material, Al material) Table-3 Particle size of metal powder (Cr-B alloy material, Al material) Table-4 Chemical composition of metal material Values (Cr-B alloy material, Al material) Table-5 Examples (Cr-B alloy material and Al material addition amount) Table-6 Examples (graphite addition amount) ~ (Table 2 to Table 4) The basic test results and examples based on these results are shown in- (Tables 5 and 6).

Test piece prototype conditions Molding pressure Based on curing temperature (1000kg / cm ² ) (350 ° C) (Effects of the Invention) As shown above, the conventional magnesia graphite material and the chromium-boron alloy-added material of the same material were treated at 1600 ° C, and the comparative materials were -0.52% and -0.
67% shows all residual shrinkage, but all the products of the present invention have the characteristic of residual expansion, and the products of the examples of the present invention are conventional magnesia-graphite in terms of the amount of erosion and the penetration depth of foreign substances such as slag. 37% to 70% and 45.5% to 80% compared to the material
And it is possible to learn a great improvement in quality. In this way, it is possible to prevent the formation of an altered layer due to the permeation of foreign matter such as slag, and the structural detachment that accompanies this, and most notably, it was possible to retain the residual expansivity as described above. As a result, the conventional product had residual shrinkage, but the joints (brick joints) were mainly opened to form a chamfered shape, resulting in localized erosion damage of the groove, which resulted in heat reception and erosion from multiple faces. By receiving it, it accelerates melting loss and promotes the phenomenon of stripping of the operating layer, and the characteristics of the material could not be fully utilized and the product had reached the end of its life.However, when used, a smooth monolithic operating surface was formed and the characteristics of the material were fully utilized. By being able to do so, stable operation can be achieved and the service life can be extended, and the effect is enormous.

Claims (1)

[Claims] 1. A graphite and / or carbonaceous material in an amount of 5% to 30%
And one or more refractory materials consisting of two or more of chromium and boron in a molar ratio of 1: 1 to 1: 2 and impure components within 10% of chromium boride alloy and Al or Al alloy 0.5 fine powder
~ 10%, and 0.5% ~ 5% are added, and the mixture is kneaded and shaped by using an appropriate organic and / or inorganic binder, and 150 ℃ ~ 1000
A graphite refractory for iron making characterized by being hardened at ℃.